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SDCC Compiler User Guide

1. lt assembly sequence gt assembly instruction each instruction including labels must be on a separate line The optimizer will apply to the rules one by one from the top in the sequence of their appearance it will terminate when all rules are exhausted If the restart option is specified then the optimizer will start matching the rules again from the top this option for a rule is expensive performance it is intended to be used in situations where a transformation will trigger the same rule again An example of this not a good one it has side effects is the following rule 98 8 2 ANSI COMPLIANCE CHAPTER 8 SDCC TECHNICAL DATA replace restart pop 1 push 1 by nop Note that the replace pattern cannot be a blank but can be a comment line Without the restart option only the innermost pop push pair would be eliminated i e pop arl pop ar2 push ar2 push arl would result in pop arl 7 nop push arl with the restart option the rule will be applied again to the resulting code and then all the pop push pairs will be eliminated to yield nop nop A conditional function can be attached to a rule Attaching rules are somewhat more involved let me illustrate this with an example replace ljmp 5 2 by sjmp 5 2 if labelInRange The optimizer does a look up of a function name table defined in function callFuncByName in the source file SDCCpeeph c with
2. sdec sourceforge net snap php and you can always build the very last version from the source code available at Sourceforge http sdcc sourceforge net snap php Source The SDCC Wiki athttp sdcc wiki sourceforge net also holds some information about past and future releases 7 8 Quality control The compiler is passed through daily snapshot build compile and build checks The so called regression tests check that SDCC itself compiles flawlessly on several host platforms 1386 Opteron 64 bit Alpha ppc64 Mac OS X on ppc and i386 Solaris on Sparc and checks the quality of the code generated by SDCC by running the code for several target platforms through simulators The regression test suite comprises more than 100 files which expand Traffic on sdcc devel and sdcc user is about 100 mails month each not counting automated messages mid 2003 89 7 9 EXAMPLES CHAPTER 7 SUPPORT to more than 500 test cases which include more than 4500 tests The results of these tests are published daily on SDCC s snapshot page click on the red or green symbols on the right side of http sdec sourceforge net snap php There is a separate document test_suite pdf http sdcc sourceforge net doc test_suite_ spec pdf about the regression test suite You ll find the test code in the directory sdcc support regression You can run these tests manually by running make in this directory or f e make test mcs51 if you don t want to run the
3. CHAPTER 6 TIPS Name Purpose Where to get gpsim PIC simulator http www dattalo com gnupic gpsim html gputils GNU PIC utilities https sourceforge net projects gputils fIPS PIC programmer http freshmeat net projects fl1p5 ec2drv newcdb Tools for Silicon Laboratories http sourceforge net projects ec2drv JTAG debug adapter partly based on SDCDB Unix only indent Formats C source Master of the http white spaces directory fsf org GNU indent html srecord Object file conversion checksum http ming sourceforge net projects srecord objdump Object file conversion Part of binutils should be there anyway cmon51 8051 monitor hex up download http sourceforge net projects cmon51 single step disassemble doxygen Source code documentation sys http www doxygen org tem kdevelop IDE has anyone tried integrating http www kdevelop org SDCC amp SDCDB Unix only paulmon 8051 monitor hex up download http single step disassemble www pjrc com tech 8051 paulmon2 html splint Statically checks c sources see http www splint org 229 ddd Debugger serves nicely as GUI to http www gnu org software ddd SDCDB Unix only d52 Disassembler can count instruc http www 8052 com users disasm tion cycles use with options pnd cmake Cross platform build system http www cmake org and a dedicated wiki generates Makefiles a
4. The debugger will look for the following files e foo c the source file e foo cdb the debugger symbol information file e foo ihx the Intel hex format object file 77 5 1 DEBUGGING WITH SDCDB CHAPTER 5 DEBUGGING 5 1 4 SDCDB Command Line Options directory lt source file directory gt this option can used to specify the directory search list The debugger will look into the directory list specified for source cdb amp ihx files The items in the directory list must be separated by e g if the source files can be in the directories home src1 and home src2 the directory option should be directory home src1 home src2 Note there can be no spaces in the option cd lt directory gt change to the lt directory gt fullname used by GUI front ends cpu lt cpu type gt this argument is passed to the simulator please see the simulator docs for details X lt Clock frequency gt this options is passed to the simulator please see the simulator docs for details s lt serial port file gt passed to simulator see the simulator docs for details S lt serial in out gt passed to simulator see the simulator docs for details k lt port number gt passed to simulator see the simulator docs for details 5 1 5 SDCDB Debugger Commands As mentioned earlier the command interface for the debugger has been deliberately kept as close the GNU debugger gdb as possible This will help the integration with exi
5. crtxinit asm area GSINIT3 CODE _ mecs51_genXINIT mov r1 1_XINIT mov a rl orl a 1_XINIT gt gt 8 jz 00003 mov r2 1_XINIT 255 gt gt 8 mov dptr s_XINIT mov r0 S_XISEG mov __XPAGE S_XISEG gt gt 8 00001 clr a move a at dptr movx r0 a inc dptr inc ro cjne r0 0 00002 inc __XPAGE 00002S djnz r1 00001 djnz r2 00001 mov __XPAGE 0xFF 000035 crtclear asm area GSINIT4 CODE __mcs51_genRAMCLEAR 44 3 12 STARTUP CODE CHAPTER 3 USING SDCC clr a mov r0 1_IRAM 1 00004S mov r0 a djnz r0 00004 _mcs51_genRAMCLEAR end crtxclear asm area GSINIT4 CODE __mcs51_genXRAMCLEAR mov r0 1_PSEG mov a r0 orl a 1_PSEG gt gt 8 jz 00006 mov rl S_PSEG mov __XPAGE S_PSEG gt gt 8 clra 00005 movx rl a inc rl djnz r0 00005 000065 mov r0 1_XSEG mov a r0 orl a 1_XSEG gt gt 8 jz 00008 mov rl 1_XSEG 255 gt gt 8 mov dptr s_XSEG clra 00007 movx dptr a inc dptr djnz r0 00007 djnz r1 00007 000085 crtxstack asm area GSINIT5 CODE Need to initialize in GSINIT5 because __mcs51_genXINIT modifies __XPAGE and __mcs51_genRAMCLEAR modifies _spx mov __XPAGE __start__xstack gt gt 8 mov _spx __start__xstack application modules area GSINIT CODE main asm area GSFINAL CODE ljmp __sdcc_program_startup area HOME CODE area CSEG CODE
6. _moduint rel _mulint rel Use sdcclib I libint lib myliblist txt Additionally you can instruct sdcclib to compile the files before adding them to the library This is achieved using the environment variables SDCCLIB_CC and or SDCCLIB_AS For example set SDCCLIB_CC sdcc c sdcclib I libint lib myliblist txt To see what modules and symbols are included in the library options s and m are available For example sdcclib s libint lib _divsint rel 24 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC _ divsi _ divsi _ divsi nt_a 1 1 nt_PARM_2 nt _divuint rel _ divui _ divui _ divui _ divui _ divui nt a 1 1 nt_PARM_2 nt_reste_1 1 nt_count_1_1 nt _modsint rel modsi modsi modsi nt_a 1 1 nt_PARM_2 nt _moduint rel modui modui modui nt_a 1 1 nt_PARM_2 nt_count_1 1 _ moduint _mulint rel _ mulint_PARM 2 _ mulint If the source files are compiled using debug the corresponding debug information file adb will be included in the library file as well The library files created with sdcclib are plain text files so they can be viewed with a text editor It is not recommended to modify a library file created with sdcclib using a text editor as there are file index numbers located across the file used by the linker to quickly locate the required module to link Once a rel file as well as a adb file is added to a library using sdcclib it can be safely deleted since all the
7. include_dir_suffix include non_free_include_dir_suffix non free include lib_dir_suffix lib non_free_lib_dir_suffix non free lib sdccconf_h_dir_separator CC gcc mno cygwin CXX g mno cygwin configure is quite slow on Cygwin at least on windows before Win2000 XP The option C turns on caching which gives a little bit extra speed However if options are changed it can be necessary to delete the config cache file 2 2 Install paths Description Path Default Win32 builds Binary files S EXEC_PREFIX usr local bin sdcec bin Include files DATADIR usr local share sdec include INCLUDE_DIR_SUFFIX sdcec include Non free include files DATADIR non free usr local share sdcc non free include INCLUDE_DIR_SUFFIX sdcc non free include Library file DATADIR usr local share sdcc lib LIB_DIR_SUF FIX sdcc lib Library file DATADIR non free usr local share sdcc non free lib LIB_DIR_SUFFIX sdcc non free lib Documentation DOCDIR usr local share sdcc doc sdcc doc 12 2 3 SEARCH PATHS CHAPTER 2 INSTALLING SDCC compiler preprocessor assembler and linker the model is auto appended by the compiler e g small large z80 ds390 etc The install paths can still be changed during make install with e g make install prefix HOME local sdcc Of course this doesn t change the search paths comp
8. re not automatically on the safe side if you use 8 bit variables though We need an example here f e on the 8051 the harmless looking flags 0x80 is not atomic if flags resides in xdata Setting flags 0x40 from within an interrupt routine might get lost if the interrupt occurs at the wrong time counter 8 is not atomic on the 8051 even if counter is located in data memory Bugs like these are hard to reproduce and can cause a lot of trouble 40 3 9 INTERRUPT SERVICE ROUTINES CHAPTER 3 USING SDCC 3 9 1 3 Common interrupt pitfall stack overflow The return address and the registers used in the interrupt service routine are saved on the stack so there must be sufficient stack space If there isn t variables or registers or even the return address itself will be corrupted This stack overflow is most likely to happen if the interrupt occurs during the deepest subroutine when the stack is already in use for f e many return addresses 3 9 1 4 Common interrupt pitfall use of non reentrant functions A special note here int 16 bit and long 32 bit integer division multiplication amp modulus and floating point operations are implemented using external support routines If an interrupt service routine needs to do any of these operations then the support routines as mentioned in a following section will have to be recompiled using the stack auto option and the source file will need to be compiled using t
9. 66 Some Questions 2 lt 2b88 8 a66H a4 bea a bee eG Ee 87 7 Support 88 TL Reporte Bugs sc x wea e Seis AR Gee Bie eS PH REE OSHS OHSS 88 2 Regues ng PESTIES o r oc p a ee OR ew ee A a o be wee a 89 T3 Submitting pathes on BAER AR ERR PAS ea ee eee 2 HAS 89 Sa ere PISS ce we Ae Sok ee ES AR 89 To ChangeLog e e oe a eee Ee Eas Rae ee eo Ee We Ea Se eae s 89 TG Subversion Source Code Repository eres p aa a a e a a G 89 Er 6 Belease poly o o A A EE a e a a A EERE 89 TS Quality contol s s spose maaie msa a a a a a a 89 9 Example a eA RAS GREASE A e See e oe e 90 7 10 Use of SDCC im Education e lt oos ee Bee RA Re Ae ER RE EEE ER Oe S 90 CONTENTS CONTENTS 8 SDCC Technical Data 91 S1 OpumMizations lt lt coo A e a do 91 3 1 1 Sub expression Elimination s s p 6 3645 bea e E ss a 91 8 12 Dead Code Elimination 25 0 50644 56805 bee thane ee ee ea es 91 SLO LOpy PrapesO ed 4 ore ee ese pe we Be ede eae Sa eos Hae os 92 8 14 pop Optimarmatone b teap 4804 po be eae eS aes ba NS Se eS 92 Sla lappRercmime 2245 4 pa 24 b4h8S eRe Pe 6 bk BEES EES S 93 5 1 6 Algebra Simpliications lt lt cae ews GAS Ae A A A 93 Se Swen DIME se os e AY we Boe bie ede eg gloves wk eS aT ede ie Sao lt 93 81 8 Bit shitting Operations lt lt lt 5 846554 ee cn a ee 95 8 19 Bitrotation 2 5 68455 bea Ree eee eee 95 8 1 10 Nibble and Byte Swapping e 96 8 1 11 Highest Order Bit Any Order Bit 2 oe ee ee ee es 96
10. Note that if any segments are located above 64K the r flag must be passed to the linker to generate the proper segment relocations and the Intel HEX output format must be used The r flag can be passed to the linker by using the option Wl r on the SDCC command line However currently the linker can not handle code segments gt 64k 3 19 Pragmas Pragmas are used to turn on and or off certain compiler options Some of them are closely related to corresponding command line options see section 3 2 on page 25 Pragmas should be placed before and or after a function placing pragmas inside a function body could have unpredictable results SDCC supports the following pragma directives e save this will save most current options to the save restore stack See pragma restore 55 3 19 PRAGMAS CHAPTER 3 USING SDCC restore will restore saved options from the last save saves amp restores can be nested SDCC uses a save restore stack save pushes current options to the stack restore pulls current options from the stack See pragma save callee_saves function function2 function3 The compiler by default uses a caller saves convention for register saving across function calls however this can cause unnecessary register pushing and popping when calling small functions from larger functions This option can be used to switch off the register saving con vention for the function names specified The compiler will not
11. __sdcc_program_startup lcall _main return from main will lock up s jmp One of these modules crtstart asm contains a call to the C routine _sdcc_external_startup at the start of the CODE area This routine is also in the runtime library and returns O by default If this routine returns a non zero value the static amp global variable initialization will be skipped and the function main will be invoked Otherwise static amp global variables will be initialized before the function main is invoked You could add an 45 3 13 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC _sdcc_external_startup routine to your program to override the default if you need to setup hardware or perform some other critical operation prior to static amp global variable initialization On some mcs51 variants xdata memory has to be explicitly enabled before it can be accessed or if the watchdog needs to be disabled this is the place to do it The startup code clears all internal data memory 256 bytes by default but from 0 to n 1 if iram sizen is used recommended for Chipcon CC1010 See also the compiler options no xinit opt main return and section 4 1 about MCS51 variants While these initialization modules are meant as generic startup code there might be the need for customiza tion Let s assume the return value of _sdcc_external_startup in crtstart asm should not be checked or _sdcc_external_startup should not be called at all The rec
12. _gint Ir0 0 int _gint 1r0 0 int iTemp17 lr23 38 int r7 r0 Sample c 15 36 42 1 iTemp21 lr21 38 short r4 Temp21 Ir21 38 short r4 0x1 short Sample c 15 37 45 1 iTemp23 Ir22 38 int r5 r6 iTemp23 lr22 38 int r5 r6 0x1 short Sample c 19 38 47 1 goto _forcond_0 4 Sample c 19 39 48 0 _forbreak_0 7 Sample c 20 40 49 0 Temp24 lr40 41 short DPTR iTemp2 1r18 40 short r2 ITemp11 Ir19 40 short 13 Sample c 20 41 50 0 ret Temp24 1r40 41 short Sample c 20 42 51 0 _return 8 Sample c 20 43 52 0 eproc _function Ir0 0 ia0 reO rm0 function short Finally the code generated for this function area DSEG DATA pu ds 2 _gint ds 2 sample c 5 gt function function _function Tempo Ir3 5 _near int r2 recv mov r2 dpl iTemp6 Ir5 16 _near int r0 iTemp0 1r3 5 _near int r2 mov ar0 r2 _whilecontinue_0 1 00101 iTemp4 Ir7 8 int r2 r3 iTemp6 Ir5 16 _near int r0 if iTemp4 lr7 8 int r2 13 0 goto _whilebreak_0 3 mov ar2 r0 inc rO mov ar3 r0 dec r0 mov a r2 orl a r3 jz 00103 00114 iTemp7 Ir9 13 _far int DPTR _p Ir0 0 _far int mov dpl _p 107 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS mov dph _p 1 _p lr0 0 _far int _p lr0 0 _far int 0x2 short mov a 0x02 add a _p mov _p a clra addc a _p 1 m
13. strength reduction of induction variables and loop reversing e constant folding amp propagation e copy propagation e dead code elimination e jump tables for switch statements For the back end SDCC uses a global register allocation scheme which should be well suited for other 8 bit MCUs The peep hole optimizer uses a rule based substitution mechanism which is MCU independent Supported data types are type width default signed range unsigned range bool 1 bit unsigned 0 1 char 8 bits 1 byte signed 128 127 0 255 short 16 bits 2 bytes signed 32 768 32 767 0 65 535 int 16 bits 2 bytes signed 32 768 32 767 0 65 535 long 32 bits 4 bytes signed 2 147 483 648 2 147 483 647 0 4 294 967 295 float 4 bytes IEEE 754 signed 1 175494351E 38 3 402823466E 38 pointer 1 2 3 or 4 bytes generic The compiler also allows inline assembler code to be embedded anywhere in a function In addition routines developed in assembly can also be called SDCC also provides an option cyclomatic to report the relative complexity of a function tions can then be further optimized or hand coded in assembly if needed These func 1 2 OPEN SOURCE CHAPTER 1 INTRODUCTION SDCC also comes with a companion source level debugger SDCDB The debugger currently uses ucSim a free open source simulator for 8051 and other micro controllers The latest SDCC version can b
14. tines are called whenever data is stored or retrieved using generic pointers These are useful for developing reusable library routines Explicitly specifying the pointer type will generate the most efficient code 3 4 1 9 Notes on MCS51 memory layout The 8051 family of microcontrollers have a minimum of 128 bytes of internal RAM memory which is structured as follows Bytes 00 1F 32 bytes to hold up to 4 banks of the registers RO to R7 Bytes 20 2F 16 bytes to hold 128 bit variables and Bytes 30 7F 80 bytes for general purpose use Additionally some members of the MCS51 family may have up to 128 bytes of additional indirectly address able internal RAM memory idata Furthermore some chips may have some built in external memory xdata which should not be confused with the internal directly addressable RAM memory data Sometimes this built in xdata memory has to be activated before using it you can probably find this information on the datasheet of the microcontroller your are using see also section 3 12 Startup Code Normally SDCC will only use the first bank of registers register bank 0 but it is possible to specify that other banks of registers keyword using should be used for example in interrupt routines By default the compiler will place the stack after the last byte of allocated memory for variables For example if the first 2 banks of registers are used and only four bytes are used for data variables it will
15. tribution sets etc You know who you are Thanks to Sourceforge http www sf net which has hosted the project since 1999 and donates sig nificant download bandwidth Also thanks to all SDCC Distributed Compile Farm members for donating CPU cycles and bandwidth for snapshot builds This document was initially written by Sandeep Dutta All product names mentioned herein may be trademarks of their respective companies Alphabetical index To avoid confusion the installation and building options for SDCC itself chapter 2 are not part of the index 110 Index __ prefix for extended keywords 100 Werror 31 acall ajmp 28 98 all callee saves 30 c 1 mode 30 callee saves 30 50 code loc lt Value gt 27 36 code size lt Value gt 28 36 codeseg lt Value gt 32 compile only 30 constseg lt Value gt 32 cyclomatic 31 data loc lt Value gt 27 36 debug 22 25 31 66 77 disable warning 31 dumlrange 32 dumpall 33 88 dumpdeadcode 32 dumpgcse 32 dumploop 32 dumplrange 33 dumprange 32 dumpraw 32 dumpregassign 33 fdollars in identifiers 32 float reent 31 funsigned char 31 1 code in asm 31 idata loc lt Value gt 27 int long reent 31 41 52 Iram size lt Value gt 28 36 46 less pedantic 31 lib path lt path gt 27 main return 31 46 model huge 28 model large 28 53 model medium 28 model small 27 mor
16. util bison hairy _bison 1 2 3 4 5 6 7 8 9 Steps c and d are needed because bison requires by default that the files bison simple and bi son hairy reside in some weird Unix directory usr local share I think So it is necessary to tell bison where those files are located if they are not in such directory That is the function of the environment variables BISON_SIMPLE and BISON_HAIRY e In the Visual C IDE click Tools Options select the Directory tab in Show directories for se lect Executable files and in the directories window add a new path c util click ok Note that you can use any other path instead of c util even the path where the Visual C tools are probably C Program Files Microsoft Visual Studio Common Tools So you don t have to execute step e That is it Open sdcc dsw in Visual Studio click build all when it finishes copy the executables from sdcc bin_vc to sdcec bin and you can compile using SDCC 2 4 6 1 2 4 7 Windows Install Using a ZIP Package Download the binary zip package from http sdcc sf net snap php and unpack it using your favorite unpacking tool gunzip WinZip etc This should unpack to a group of sub directories An example directory structure after unpacking the mingw32 package is c sdcc bin for the executables c sdcc include and c sdcc lib for the include and libraries Adjust your environment
17. 34 46 Feature request 9 89 Flags 35 Flat 24 DS390 memory model 55 Floating point support 41 52 53 100 FPGA field programmable gate array 18 FpgaC subset of C to FPGA compiler 18 function epilogue 30 48 function parameter 39 50 51 function pointer 36 function pointers 50 function prologue 30 48 56 GBZ80 29 Options callee saves bc 29 codeseg lt Value gt 29 constseg lt Value gt 29 ba lt Num gt 29 bo lt Num gt 29 gbz80 GameBoy Z80 26 61 gcc GNU Compiler Collection 26 gdb 77 generic pointer 50 getchar 53 Global subexpression elimination 32 GNU General Public License GPL 7 GNU Lesser General Public License LGPL 54 gpsim pic simulator 86 gputils pic tools 63 86 HC08 26 27 37 41 46 62 interrupt 41 42 Options out fmt elf 27 Storage class 37 __hce08 59 HD64180 see Z180 37 Header files 35 83 84 heap malloc 54 Higher Order Byte 97 Higher Order Word 97 Highest Order Bit 96 HTML version of this document 18 T O memory Z80 Z180 37 ICE in circuit emulator 76 iCode 32 103 106 idata mcs51 ds390 storage class 27 34 36 __idata mcs51 ds390 storage class 34 36 IDE 31 87 Include files 35 83 84 indent source formatting tool 86 Install paths 12 Install trouble shooting 19 Installation 10 instruction cycles count 86 int 16 bit 52 int 64 bit not supported 100 Intel h
18. 8 1 12 Higher Order Byte Higher Order Word o 97 1 13 Peephole Optimizer ea ew eb Ba be wee ee E A 98 G2 ADSL OMDIADES o bas bw ee a Set be db eet BAS 99 2 Cyclone Complex 0 cos ee CG Re ee E ERE RR A E A 101 34 Retargetting for other Processors s eacee ew Re a e eR RR 101 9 Compiler internals 103 9 1 The anatomy ol Mi compller 2 05066 so eA Ae ea Re eee ee 103 9 2 A few words about basic block successors predecessors and dominators 109 10 Acknowledgments 110 Chapter 1 Introduction 1 1 About SDCC SDCC Small Device C Compiler is free open source retargettable optimizing ANSI C compiler by Sandeep Dutta designed for 8 bit Microprocessors The current version targets Intel MCS51 based Microprocessors 8031 8032 8051 8052 etc Dallas DS80C390 variants Freescale formerly Motorola HCO08 and Zilog Z80 based MCUs It can be retargeted for other microprocessors support for Microchip PIC is under development The entire source code for the compiler is distributed under GPL SDCC uses a modified version of ASXXXX amp ASLINK free open source retargetable assembler amp linker SDCC has extensive language extensions suitable for utilizing various microcontrollers and underlying hardware effectively In addition to the MCU specific optimizations SDCC also does a host of standard optimizations like e global sub expression elimination e loop optimizations loop invariant
19. If you include the file z180 h this will be set automatically 3 4 3 HC08 Storage Class Language Extensions 3 4 3 1 data The data storage class declares a variable that resides in the first 256 bytes of memory the direct page The HC08 is most efficient at accessing variables especially pointers stored here 3 4 3 2 xdata The xdata storage class declares a variable that can reside anywhere in memory This is the default if no storage class is specified 3 5 Other SDCC language extensions 3 5 1 Binary constants SDCC supports the use of binary constants such as 0b01100010 This feature is only enabled when the compiler is invoked using std sdccxx 37 3 6 ABSOLUTE ADDRESSING CHAPTER 3 USING SDCC 3 6 Absolute Addressing Data items can be assigned an absolute address with the at lt address gt keyword in addition to a storage class e g _ xdata __at 0x7ffe unsigned int chksum In the above example the variable chksum will be located at Ox7ffe and Ox7fff of the external ram The compiler does not reserve any space for variables declared in this way they are implemented with an equate in the assembler Thus it is left to the programmer to make sure there are no overlaps with other variables that are declared without the absolute address The assembler listing file lst and the linker output files rst and map are good places to look for such overlaps If however you provide an initializer actual memory allo
20. Obviously this has pros and cons 1 5 SYSTEM REQUIREMENTS CHAPTER 1 INTRODUCTION 1 5 bit and sbit types now consistently behave like the C99 _Bool type with respect to type conversion The most common incompatibility resulting from this change is related to bit toggling idioms e g pit D b b equivalent to b 1 instead of toggling b b b toggles b x In previous versions both forms would have toggled the bit in older versions the preprocessor was always called with std c99 regardless of the std xxx setting This is no longer true and can cause compilation failures on code built with std c89 but using c99 preprocessor features such as one line comments in versions older than 2 8 4 the pic16 printf and printf_tiny library functions supported undocumented and not standard compliant b binary format specifier b hb and lb The b specifier is now disabled by default It can be enabled by defining BINARY_SPECIFIER macro in files de vice lib pic16 libc stdio vfprintf c and device lib pic16 libe stdio printf_tiny c and recompiling the library in versions older then 2 8 5 the unnamed bitfield structure members participated in initialization which is not conforming with ISO IEC 9899 1999 standard see section Section 6 7 8 Initialization clause 9 Old behavior before version 2 8 5 struct int a 2 char 2 int b 2 s 1 2 3 x s a 1 s b 3 x New behav
21. SDCC 2 4 1 Building SDCC on Linux 1 Download the source package either from the SDCC Subversion repository or from snapshot builds it will be named something like sdcc src yyyymmdd rrrr tar bz2 http sdcc sourceforge net snap php 2 Bring up a command line terminal such as xterm W Unpack the file using a command like tar xvjf sdcc src yyyymmdd rrrr tar bz2 this will create a sub directory called sdcc with all of the sources Change directory into the main SDCC directory for example type cd sdcc Type configure This configures the package for compilation on your system Type make All of the source packages will compile this can take a while ID UU pa Type make install as root This copies the binary executables the include files the libraries and the documentation to the install directories Proceed with section 2 7 14 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC 2 4 2 Building SDCC on Mac OS X Follow the instruction for Linux On Mac OS X 10 2 x it was reported that the default gec version 3 1 20020420 prerelease fails to com pile SDCC Fortunately there s also gcc 2 9 x installed which works fine This compiler can be selected by running configure with configure CC gcc2 CXX g 2 Universal ppc and 1386 binaries can be produced on Mac OS X 10 4 x with Xcode Run configure with configure LDFLAGS W1 syslibroot Developer SDKs MacOSX10 4
22. _nakea or the callee saves all callee saves command line option or the corresponding callee_saves pragma are used the caller will save the registers RO R7 around the call so the called function can destroy they content freely If the called function is not declared as _naked the caller will swap register banks around the call if caller and callee use different register banks having them defined by the _using modifier The called function can also use DPL DPH B and ACC observing that they are used for parameter return value passing 3 14 3 Assembler Routine non reentrant In the following example the function c_func calls an assembler routine asm_func which takes two parameters extern int asm_func unsigned char unsigned char int c_func unsigned char i unsigned char j return asm_func i j int main return c_func 10 9 The corresponding assembler function is globl _asm_func_PARM_2 globl _asm_func area OSEG asm_func_PARM_2 ds 1 area CSEG asm_func mov a dpl add a _asm_func_PARM 2 mov dpl a mov dph 0x00 ret The parameter naming convention is _ lt function_name gt _PARM_ lt n gt where n is the parameter number starting from 1 and counting from the left The first parameter is passed in DPH DPL B and ACC according to the 50 3 14 INTERFACING WITH ASSEMBLER CODE CHAPTER 3 USING SDCC description above The variable name for the second par
23. a function 58 3 20 DEFINES CREATED B Y THE COMPILER CHAPTER 3 USING SDCC 3 20 Defines Created by the Compiler The compiler creates the following defines define Description SDCC Always defined Since version 2 5 6 the version number as an int ex 256 SDCC_mcs51 or SDCC_ds390 or SDCC_z80 etc depending on the model used e g mds390 _mes51 __ds390 __hc08 __z80 etc depending on the model used e g mz80 SDCC_STACK_AUTO when stack auto option is used SDCC_MODEL_SMALL when model small is used SDCC_MODEL_MEDIUM when model medium is used SDCC_MODEL_LARGE when model large is used SDCC_MODEL_HUGE when model huge is used SDCC_USE_XSTACK when xstack option is used SDCC_CHAR_UNSIGNED when funsigned char option is used SDCC_STACK_TENBIT when mds390 is used SDCC_MODEL_FLAT24 when mds390 is used SDCC_REVISION Always defined SDCC svn revision number SDCC_PARMS_IN_BANK1 when parms in bankl is used SDCC_FLOAT_REENT when float reent is used SDCC_INT_LONG_REENT when int long reent is used 59 Chapter 4 Notes on supported Processors 4 1 MCSSI variants MCS31 processors are available from many vendors and come in many different flavours While they might differ considerably in respect to Special Function Registers the core MCS51 is usually not modified or i
24. b 00001 __endasm Inline assembler code cannot reference any C labels however it can reference labels defined by the inline assembler e g foo some c code x __asm some assembler cod ljmp 0003 __ endasm some more c code x clabel inline assembler cannot reference this label 8 __asm 00035 label can be referenced by inline assembler only __endasm some more c code x In other words inline assembly code can access labels defined in inline assembly within the scope of the function The same goes the other way i e labels defines in inline assembly can not be accessed by C statements 7This is a slightly more stringent rule than absolutely necessary but stays always on the safe side Labels in the form of nnnnn are local labels in the assembler locality of which is confined within two labels of the standard form The compiler uses the same form for labels within a function but starting from nnnnn 00100 and places always a standard label at the beginning of a function thus limiting the locality of labels within the scope of the function So if the inline assembler part would be embedded into C code an improperly placed non local label in the assembler would break up the reference space for labels created by the compiler for the C code leading to an assembling error The numeric part of local labels does not need to have 5 digits although this is the form of labels output by the compiler an
25. can be used to switch the register saving convention for the function names specified The compiler will not save registers when calling these functions no extra code will be generated at the entry and exit function prologue and epilogue for these functions to save and restore the registers used by these functions this can SUBSTANTIALLY reduce code and improve run time performance of the generated code In the future the compiler with inter procedural analysis will be able to determine the appropriate scheme to use for each function call DO NOT use this option for built in functions such as _mulint if this option is used for a library function the appropriate library function needs to be recompiled with the same option If the project consists of multiple source files then all the source file should be compiled with the same callee saves option string Also see pragma callee_saves on page 56 all callee saves Function of callee saves will be applied to all functions by default 30 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC debug When this option is used the compiler will generate debug information The debug information col lected in a file with cdb extension can be used with the SDCDB For more information see documen tation for SDCDB Another file with no extension contains debug information in AOMF or AOMF51 format which is commonly used by third party tools S Stop after the stage of compilation proper do not as
26. deprecated and will cause the stack pointer to cross page boundaries or even exceed the available data RAM and crash the program Make sure that stack does not cross page boundaries when using the SMALL stack model 67 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS code Force a function to a static FLASH address Example place function test_func at 0x4000 x pragma code test_func 0x4000 library instructs the linker to use a library module Usage pragma library module_name module_name can be any library or object file including its path Note that there are four reserved keywords which have special meaning These are Keyword Description Module to link ignore ignore all library pragmas none c link the C library libc18f 11b math link the Math libarary libm18f 11b io link the 1 O library libio18f 11b debug link the debug library libdebug lib is the device number 1 e 452 for PICI8F452 MCU This feature allows for linking with specific libraries without having to explicit name them in the command line Note that the IGNORE keyword will reject all modules specified by the library pragma udata The pragma udata instructs the compiler to emit code so that linker will place a variable at a specific memory bank Example places variable foo at bank2 x pragma udata bank2 foo char foo In order for this pragma to work extra SECTION directives
27. eee 64 45 5 Punchonareuments o o eek Gee Set es See Se BS 64 552 Wegressiontesteiall ss coser Pe ke ew ERG E Soe 64 a Mie PCIe per x Bas eed beg Bee eee te ae o a a ae eke Oe et Bae 65 AGI Glopa OpPHONS s lt eop ee SR eR eR OE EER OR RS eR OS 65 26 2 Porm Specie CIPMODS n ico ra eee Dee ec Bebe eho 65 4 6 2 1 Code Generation Options s se cse 25 6 bb he ek a ke ee 65 4622 Optimization Options lt lt s c eree ee ew ee ee ee es 65 45 2 9 Assembling Opuens o cc BG a a a AGE awe eG So 66 4624 Linking Opies 044 644 4664 46 eve Pow a A eas 66 4 5 2 5 Debugging Options lt s se c sosen eA DRE RS ROS 66 46 3 Epvitonment Variables lt 64 e004 Pe A eee es ES Gee eee a 66 CONTENTS CONTENTS 404 Preprocessor Matros cae a a a ES GE SS SS 67 AOS o oe Sw eee eh Eee Bebe eA ee ee te 67 AGO PRIMAS co bs eA e a a Ree ad a ea ee aS 67 4 6 7 Header Piles add Libtanes os c csser ero rrepat rine oe ESS 69 A06 Header Files 2 2 cied y ac Hae ede a Re eA A S RAE a eS 69 AO LIBERE 2x cook o Hae te Boe a be oe ee Gee bs BG oe EA 69 46 10 Adding New Devices tothe Port s ooo 2224 ped aE RA SE PS 70 Aol Memory Models obscena Be es BORG Wee we es 70 OTD MIME eoa eaae a e E eA a aa a eee a See 71 BANS o s se pa aup ee s A E E en hee be a a 71 46 14 F nctionret tn values lt s s oa ee RA EER TEE EA 72 ALGAAS o i eb woe Ae Be yw ego we Aree Be ede oaa eee now amp Bs ge ale 72 dolo Genere Pointers ii w
28. in sequence of execution dumpgcse Will create a dump of iCodes after global subexpression elimination into a file named lt source filename gt dumpgcse dumpdeadcode Will create a dump of iCodes after deadcode elimination into a file named lt source file name gt dumpdeadcode dumploop Will create a dump of iCodes after loop optimizations into a file named lt source file name gt dumploop dumprange Will create a dump of iCodes after live range analysis into a file named lt source file name gt dumprange dumlrange Will dump the life ranges for all symbols 32 3 3 ENVIRONMENT VARIABLES CHAPTER 3 USING SDCC dumpregassign Will create a dump of iCodes after register assignment into a file named lt source file name gt dumprass gn dumplrange Will create a dump of the live ranges of iTemp s dumpall Will cause all the above mentioned dumps to be created 3 2 11 Redirecting output on Windows Shells By default SDCC writes its error messages to standard error To force all messages to standard out put use use stdout Additionally if you happen to have visual studio installed in your windows machine you can use it to compile your sources using a custom build and the SDCC ve option Something like this should work c sdcc bin sdcc exe ve model large c InputPath 3 3 Environment variables SDCC recognizes the following environment variables SDCC_LEAVE_SIGNALS SDCC in
29. information required for linking is embedded in the library file itself Library files created using sdcclib are used as described in the preceding sections 3 1 6 Using ar to Create and Manage Libraries Support for ar format libraries was introduced in sdcc 2 9 0 Aris a standard archive managing utility on unices Linux Mac OS X several unix flavors so it is not included in the sdcc package For Windows platform you can find ar utility in GNU binutils package included in several projects Cyg win at http www cygwin com MinGW at http www mingw org Both the GNU and BSD ar format variants are supported by sdld linkers Ar doesn t natively understand the sdas object file format so there is a special version of ranlib distributed with sdcc called asranlib which produces the ar symbol lookup table To create a library containing sdas object files you should use the following sequence ar Sq lt library name gt lib lt list of rel files gt asranlib lt library name gt lib 3 2 Command Line Options 3 2 1 Processor Selection Options mmcs51 Generate code for the Intel MCS51 family of processors This is the default processor target mds390 Generate code for the Dallas DS80C390 processor mds400 Generate code for the Dallas DS80C400 processor 25 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC mhc08 Generate code for the Freescale Motorola HC08 family of processors mz80 Generate code for the Zilog Z80 fami
30. lack of a better term In this case several MCU specific expression folding is done to reduce register pressure The second part is more MCU independent and deals with allocating registers to the remaining live ranges A lot of MCU specific code does creep into this phase because of the limited number of index registers available in the 8051 e The Code generation phase is unhappily entirely MCU dependent and very little if any at all of this code can be reused for other MCU However the scheme for allocating a homogenized assembler operand for each iCode operand may be reused e As mentioned in the optimization section the peep hole optimizer is rule based system which can repro grammed for other MCUs More information is available on SDCC Wiki preliminary link http sdcc wiki sourceforge net SDCCt internalstand porting and in the thread http sf net mailarchive message php msg_id 13954144 102 Chapter 9 Compiler internals 9 1 The anatomy of the compiler This is an excerpt from an article published in Circuit Cellar Magazine in August 2000 It s a little outdated the compiler is much more efficient now and user developer friendly but pretty well exposes the guts of it all The current version of SDCC can generate code for Intel 8051 and Z80 MCU It is fairly easy to retarget for other 8 bit MCU Here we take a look at some of the internals of the compiler Parsing Parsing the input source file and creating an
31. mpicl4 phelp foo c foo c must exist 4 5 1 PIC Code Pages and Memory Banks The linker organizes allocation for the code page and RAM banks It does not have intimate knowledge of the code flow It will put all the code section of a single asm file into a single code page In order to make use of multiple code pages separate asm files must be used The compiler assigns all static functions of a single c file into the same code page To get the best results follow these guidelines 1 Make local functions static as non static functions require code page selection overhead Due to the way sdcc handles functions place called functions prior to calling functions in the file wherever possible Otherwise sdcc will insert unnecessary pagesel directives around the call believing that the called function is externally defined 2 For devices that have multiple code pages it is more efficient to use the same number of files as pages Use up to 4 separate c files for the 16F877 but only 2 files for the 16F874 This way the linker can put the code for each file into different code pages and there will be less page selection overhead 3 And as for any 8 bit micro especially for PIC14 as they have a very simple instruction set use unsigned char wherever possible instead of int 62 4 5 THE PIC14 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 5 2 Adding New Devices to the Port Adding support for a new 14 bit PIC MCU re
32. name to use DEF_INTLOW name begin the definition of the interrupt dispatch table fo low priority interrupt name is the function name to use DEF_HANDLER sig handler define a handler for signal sig END_DEF end the declaration of the dispatch table Additionally there are two more macros to simplify the declaration of the signal handler SIGHANDLER handler this declares the function prototype for the handler function SIGHANDLERNAKED handler same as SIGHANDLER but declares a naked function An example of using the macros above is shown below 74 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS include lt picl8fregs h gt tinclude lt signal h gt DEF_INTHIGH high_int DEF_HANDLER SIG_TMRO _tmr0_handler DEF_HANDLER SIG_BCOL _bcol_handler END_DEF SIGHANDLER _tmr0_handler x action to be taken when timer 0 overflows SIGHANDLERNAKED _bcol_handler __asm action to be taken when bus collision occurs retfie __ endasm NOTES Special care should be taken when using the above scheme e do not place a colon at the end of the DEF_ and END_DEF macros e when declaring SIGHANDLERNAKED handler never forget to use retfie for proper returning 4 6 18 PIC16 Port Tips Here you can find some general tips for compiling programs with SDCC pic16 4 6 18 1 Stack size The default stack size that is 64 bytes probably is e
33. option but that has not been tested It is incompatible with the xstack option It also only makes sense if the processor is in 24 bit contiguous addressing mode see the model flat24 option stack probe insert call to function __stack_probe at each function prologue tini libid lt nnnn gt LibraryID used in mTININative use accelerator generate code for DS390 Arithmetic Accelerator 28 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC 3 2 6 Z80 Options Callee saves bc Force a called function to always save BC no std crt When linking skip the standard crt0 rel object file You must provide your own crt0 rel for your system when linking portmode lt Value gt Determinate PORT I O mode lt Value gt is z80 or z180 asm lt Value gt Define assembler name lt Value gt is rgbds sdasz80 isas or z80asm codeseg lt Value gt Use lt Value gt for the code segment name constseg lt Value gt Use lt Value gt for the const segment name 3 2 7 GBZ80 Options callee saves bc Force a called function to always save BC no std crt When linking skip the standard crt0 rel object file You must provide your own crt0 rel for your system when linking bo lt Num gt Use code bank lt Num gt ba lt Num gt Use data bank lt Num gt codeseg lt Value gt Use lt Value gt for the code segment name constseg lt Value gt Use lt Value gt for the const segment name 3 2 8 Optimization Optio
34. position the base of the internal stack at address 20 0x14 This implies that as the stack grows it will use up the remaining register banks and the 16 bytes used by the 128 bit variables and 80 bytes for general purpose use If any bit variables are used the data variables will be placed in unused register banks and after the byte holding the last bit variable For example if register banks 0 and 1 are used and there are 9 bit variables two bytes used data variables will be placed starting from address 0x10 to 0x20 and continue at address 0x22 You can also use data loc to specify the start address of the data and iram size to specify the size of the total internal RAM data idata By default the 8051 linker will place the stack after the last byte of i data variables Option stack loc allows you to specify the start of the stack i e you could start it after any data in the general purpose area If your microcontroller has additional indirectly addressable internal RAM idata you can place the stack on it You may also need to use xdata loc to set the start address of the external RAM xdata and xram size to specify 1ts size Same goes for the code memory using code loc and code size If in doubt don t specify any options and see if the resulting memory layout is appropriate then you can adjust it 36 3 5 OTHER SDCC LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC The linker generates two files with memory allocation
35. should be added in the Ikr script In the following example a sample Ikr file is shown Sample lin LIB COD COD COD COD COD COD ACC PATH EPAGE EPAGE EPAGE EPAGE EPAGE EPAGE ESSBANK DATABANK DATABAN DATABAN DATABAN DATABAN DATABAN ESSBANK ACC NANNAN ION ION ION ION ION nadan un Awww wt ION SEC ION AN ge A eee DA AS E SAA AN AN DN ae ae See DA AS A Z D prprrrrrprrprrprprerrrrererere ker script for the PIC18F452 processor E vectors START 0x0 E page START 0x2A E idlocs START 0x200000 E config START 0x300000 E devid START 0x3FFFFE E eedata START 0xF00000 E accessram START 0x0 E gpr0 START 0x80 E gprl START 0x100 E gpr2 START 0x200 E gpr3 START 0x300 E gpr4 START 0x400 E gpr5 START 0x500 E accesssfr START 0xF80 E CONFIG ROM conf ig E bank0 RAM gpr0 E bank1 RAM gpr1 E bank2 RAM gpr2 E bank3 RAM gpr3 E bank4 RAM gpr4 E bank5 RAM gpr5 END 0x29 END 0x7FFF END 0 END 0 END 0 END 0 END 0x7F END 0xFF END 0x1FF END 0x2FF END 0x3FF END 0x4FF END 0x5FF END 0xFFF these SI x200007 x30000D X3FFFFF xFOOOFF PRO PRO EC ED PRO EC ED PRO EC ED PRO EC ED PROT ECTION directives should be added to link section name a specific DATABAN
36. than other compilers Eventually insert explicit casts to char or unsigned char Also check that the operator is not used on bit variables use the operator instead See sections 6 and 1 4 check the assembly code generated for interrupt routines f e for calls to possibly non reentrant library functions check whether timing loops result in proper timing or preferably consider a rewrite of the code with timer based delays instead check for differences in printf parameters some compilers push va_arg char variables as int others push them as char See section 1 4 Provide a putchar function if needed check the resulting memory map Usage of different memory spaces code stack data for mcs51 ds390 additionally idata pdata xdata Eventually check if unexpected library functions are included 83 6 2 TOOLS INCLUDED IN THE DISTRIBUTION CHAPTER 6 TIPS 6 2 Tools included in the distribution Name Purpose Directory uCsim Simulator for various architectures sdcc sim ucsim keil2sdcc pl header file conversion sdcc support scripts mh2h c header file conversion sdcc support scripts sdasgb Assembler sdcc bin sdasz80 Assembler sdcc bin sdas805 1 Assembler sdcc bin sdas6808 Assembler sdcc bin SDCDB Simulator sdcc bin sdld Linker sdcc bin sdldz80 Linker sdcc bin sdldgb Linker sdcc bin sd1d6808 Linker sdcc bin packihx Intel Hex packer sdcc bin
37. the interface to work This can be done at XEmacs startup time by inserting the following into your xemacs file which can be found in your HOME directory load file sdcdbsrc el xemacs is a lisp file so the around the command is REQUIRED The files can also be loaded dynami cally while XEmacs is running set the environment variable EMACSLOADPATP to the installation bin directory lt installdir gt bin then enter the following command ESC x load file sdedbsrc To start the interface enter the following command ESC x sdedbsrc You will prompted to enter the file name to be debugged The command line options that are passed to the simulator directly are bound to default values in the file sdcdbsrc el The variables are listed below these values maybe changed as required e sdedbsre cpu type 51 e sdedbsre frequency 11059200 e sdcdbsrc serial nil The following is a list of key mapping for the debugger interface 7 Current Listing j key binding Comment TR rr en sdcdb next from src SDCDB next command O sdcdb back from src SDCDB back command Pp o sdcdb cont from src SDCDB continue command jji sS sdcdb step from src SDCDB step command iy 2 sdcdb whatis c sexp SDCDB ptypecommand for data at it buffer point 77 X sdcdbsrc delete SDCDB Delete all breakpoints if no arg a given or delete arg C u arg x ape Mm sdcdbsrc frame SDCDB Display current frame 80 5 1 DEBUGGING WITH SDCDB CHAPTER 5 D
38. the name labelInRange If it finds a corresponding entry the function is called Note there can be no parameters specified for these functions in this case the use of 5 is crucial since the function la belInRange expects to find the label in that particular variable the hash table containing the variable bindings is passed as a parameter If you want to code more such functions take a close look at the function labelInRange and the calling mechanism in source file SDCCpeeph c Currently implemented are labelInRange labelRefCount labelIsReturnOnly operandsNotSame xramMovcOption 24bitMode portIsDS390 24bitModeAndPortDS390 and notVolatile I know this whole thing is a little kludgey but maybe some day we will have some better means If you are looking at this file you will see the default rules that are compiled into the compiler you can add your own rules in the default set there if you get tired of specifying the peep file option 8 2 ANSI Compliance The latest publicly available version of the standard ISO IEC 9899 Programming languages C should be available at http www open std org jtcl sc22 wg14 www standards html 9899 Deviations from the compliance e in some ports e g mcs51 functions are not reentrant unless explicitly declared as such or the stack auto command line option is specified e structures and unions cannot be assigned values directly cannot be passed as function parameters or assigned to each othe
39. the temporary is used only for a conditional jump the code generation makes use of this information to optimize a compare and jump ICode There are several loop optimizations performed by the compiler It can detect induction variables Temp21 1 and iTemp23 j Also note the compiler does selective strength reduction i e the multiplication of an induction variable in line 18 gint j 3 is changed to addition a new temporary iTemp17 is allocated and assigned a initial value a constant 3 is then added for each iteration of the loop The compiler does not change the multiplication in line 17 however since the processor does support an 8 8 bit multiplication 106 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS Note the dead code elimination optimization eliminated the dead assignments in line 7 amp 8 to I and sum respectively Sample c 5 1 0 0 _entry 9 Sample c 5 2 1 0 proc _function lr0 0 function short Sample c 11 3 2 0 iTemp0 Ir3 5 _near int r2 recv Sample c 11 4 53 0 preHeaderLbl0 11 Sample c 11 5 55 0 Temp6 1r5 16 _near int r0 Tempo 1r3 5 _near int r2 Sample c 11 6 5 1 _whilecontinue_0 1 Sample c 11 7 7 1 iTemp4 Ir7 8 int r2 r3 iTemp6 Ir5 16 _near int rO Sample c 11 8 8 1 if Temp4 Ir7 8 int r2 13 0 goto _whilebreak_0 3 Sample c 11 9 14 1 iTemp7 1r9 13 _far int DPTR _p 1r0 0 _far int Sample c 11 10 15 1 _p Ir
40. these can be implemented by manipulating the interrupt mask and reenabling interrupts within the interrupt routine Check there is sufficient space on the stack and don t add complexity unless you have to 3 10 3 Semaphore locking mcs51 ds390 Some architectures mcs51 ds390 have an atomic bit test and clear instruction These type of instructions are typically used in preemptive multitasking systems where a routine f e claims the use of a data structure acquires a lock on it makes some modifications and then releases the lock when the data structure is consistent again The instruction may also be used if interrupt and non interrupt code have to compete for a resource With the atomic bit test and clear instruction interrupts don t have to be disabled for the locking operation SDCC generates this instruction if the source follows this pattern volatile bit resource_is_free if resource_is_free resource_is_free 0 resource_is_free 1 Note mcs51 and ds390 support only an atomic bit test and clear instruction as opposed to atomic bit test and set 3 11 Functions using private register banks mcs51 ds390 Some architectures have support for quickly changing register sets SDCC supports this feature with the using attribute which tells the compiler to use a register bank other than the default bank zero It should only be applied to interrupt functions see footnote below This will in most circumstances mak
41. void nakedInterrupt void __interrupt 2 __naked __asm inc _counter does not change flags no need to save psw reti MUST explicitly include ret or reti in _naked function __endasm For an 8051 target the generated simpleInterrupt looks like Note this is an outdated example recent versions of SDCC generate the same code for simplelnterrupt and nakedInterrupt _simplelnterrupt push acc push b push dpl push dph push psw mov psw 0x00 48 3 13 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC inc _counter pop psw pop dph pop dpl pop b pop acc reti whereas nakedInterrupt looks like _nakedInterrupt inc _counter does not change flags no need to save psw reti MUST explicitly include ret or reti in _naked function The related directive pragma exclude allows a more fine grained control over pushing amp popping the registers While there is nothing preventing you from writing C code inside a_naked function there are many ways to shoot yourself in the foot doing this and it is recommended that you stick to inline assembler 3 13 3 Use of Labels within Inline Assembler SDCC allows the use of in line assembler with a few restrictions regarding labels All labels defined within inline assembler code have to be of the form nnnnn where nnnnn is a number less than 100 which implies a limit of utmost 100 inline assembler labels per function __asm mov b 10 00001 d3nz
42. 0 13k50 14k50 18F 2220 2221 2320 2321 2331 23k20 18F 2410 2420 2423 2431 2450 2455 2480 24310 24350 24k20 18F 2510 2515 2520 2523 2525 2550 2580 2585 25310 25550 25k20 18F 2610 2620 2680 2682 2685 2650 26k20 18F 4220 4221 4320 4321 4331 43k20 18F 4410 4420 4423 4431 4450 4455 4480 44310 44350 44k20 18F 4510 4515 4520 4523 4525 4550 4580 4585 45310 45350 45k20 18F 4610 4620 4680 4682 4685 46350 46k20 18F 6520 6527 6585 6550 18F 6620 6622 6627 6680 6650 66355 66j60 66j65 18F 6720 6722 67 50 67360 18F 8520 8527 8585 85150 18F 8620 8622 8627 8680 86350 86355 86360 86j65 18F 8720 8722 87 50 87360 18F 96360 96165 97360 An up to date list of supported devices is also available via sdcc mpicl6 plist 4 6 1 Global Options PIC16 port supports the standard command line arguments as supposed with the exception of certain cases that will be mentioned in the following list Callee saves See all callee saves fomit frame pointer Frame pointer will be omitted when the function uses no local variables 4 6 2 Port Specific Options The port specific options appear after the global options in the sdcc help output 4 6 2 1 Code Generation Options These options influence the generated assembler code pstack model model Used in conjunction with the command above Defines the stack model to be used valid stack models are small S
43. 0 0 _far int _p lr0 0 _far int 0x2 short Sample c 11 13 18 1 iTemp10 Ir13 14 int r2 r3 E iTemp7 1r9 13 _far int DPTR Sample c 11 14 19 1 Temp6 Ir5 16 _near int r0 iTemp10 Ir13 14 int r2 r3 Sample c 11 15 12 1 Temp6 Ir5 16 _near int r0 iTemp6 Ir5 16 _near int r0 0x2 short Sample c 11 16 20 1 goto _whilecontinue_0 1 Sample c 11 17 21 0 _whilebreak_0 3 Sample c 12 18 22 0 iTemp2 1r18 40 short r2 0x0 short Sample c 13 19 23 0 iTemp11 Ir19 40 short r3 0x0 short Sample c 15 20 54 0 preHeaderLbl1 13 Sample c 15 21 56 0 Temp21 Ir21 38 short r4 0x0 short Sample c 15 22 57 0 Temp23 Ir22 38 int 15 r6 Oxa int Sample c 15 23 58 0 iTemp17 Ir23 38 int r7 r0 Oxle int Sample c 15 24 26 1 _forcond_0 4 Sample c 15 25 27 1 iTemp13 Ir25 26 char CC iTemp21 Ir21 38 short 14 lt Oxa short Sample c 15 26 28 1 if iTemp13 Ir25 26 char CC 0 goto _forbreak_0 7 Sample c 16 27 31 1 iTemp2 Ir18 40 short r2 iTemp2 Ir18 40 short r2 ITemp21 Ir21 38 short r4 Sample c 17 29 33 1 iTemp15 Ir29 30 short r1 Temp21 lr21 38 short r4 0x3 short Sample c 17 30 34 1 iTemp11 Ir19 40 short r3 Temp11 Ir19 40 short r3 Temp15 Ir29 30 short r1 Sample c 18 32 36 1 1 iTemp17 Ir23 38 int 17 r0 iTemp17 lr23 38 int r7 r0 0x3 short Sample c 18 33 37 1
44. 12 signed char 3 No the result is not 4 int unsigned char 12 int signed char 3 int unsigned char 0xf4 int signed char Oxfd int 0x00 4 int Oxfffd int 0x00 4 int Oxfffd int 244 int 3 int 81 int Oxffaf Don t complain that gcc gives you a different result gcc uses 32 bit ints while SDCC uses 16 bit ints Therefore the results are different From comp lang c FAQ Ifwell defined overflow characteristics are important and negative values are not or ifyou want to steer clear of sign extension problems when manipulating bits or bytes use one of the cor responding unsigned types Beware when mixing signed and unsigned values in expressions though Although character types especially unsigned char can be used as tiny integers doing so is sometimes more trouble than it s worth due to unpredictable sign extension and increased code size e Use unsigned when it is known in advance that the value is not going to be negative This helps especially if you are doing division or multiplication bit shifting or are using an array index 82 6 1 PORTING CODE FROM OR TO OTHER COMPILERS CHAPTER 6 TIPS 6 1 NEVER jump into a LOOP Declare the variables to be local whenever possible especially loop control variables induction Have a look at the assembly listing to get a feeling for the code generation Porting code from or to other compilers
45. 26 v 30 lt NO FLOAT gt 53 69 lt file gt no extension 22 lt file gt adb 22 77 lt file gt asm 22 lt file gt cdb 22 77 lt file gt dump 22 lt file gt ihx 22 lt file gt lib 23 lt file gt Ink 23 lt file gt 1st 22 38 lt file gt map 22 37 38 lt file gt mem 22 37 lt file gt rel 22 24 lt file gt rst 22 38 lt file gt sym 22 lt stdio h gt 53 Operator 8 83 8031 8032 8051 8052 mcs51 CPU 6 Absolute addressing 38 39 ACC mcs51 ds390 register 50 Aligned array 38 46 47 Annotated syntax tree 103 ANSI compliance 7 99 Any Order Bit 96 AOMF AOMF5S1 22 31 76 77 Application notes 86 ar 25 __asm 47 49 _asm 42 47 49 Assembler documentation 48 84 Assembler listing 22 Assembler options 31 Assembler routines 42 46 50 98 Assembler routines non reentrant 50 Assembler routines reentrant 51 Assembler source 22 at 35 37 39 46 __at 35 37 38 46 atomic 40 43 B mcs51 ds390 register 50 backfill unused memory 23 banked 61 Bankswitching 60 Basic blocks 32 109 bit 8 27 35 36 38 39 83 __ bit 35 Bit rotation 95 Bit shifting 95 Bit toggling 8 bitfields 35 block boundary 38 Bug reporting 88 Building SDCC 14 Byte swapping 96 C FAQ 86 C Reference card 86 Carry flag 35 Changelog 89 checksum 23 cmake 86 code 27 32 34 _ code 34 code banking 60 code banking limited support 9 c
46. A picture speaks a thousand words ICode example sections show the live range annotations for each of the operand It is important to note here each iCode is assigned a number in the order of its execution in the function The live ranges are computed in terms of these numbers The from number is the number of the iCode which first defines the operand and the to number signifies the iCode which uses this operand last Register Allocation The register allocation determines the type and number of registers needed by each operand In most MCUs only a few registers can be used for indirect addressing In case of 8051 for example the registers RO amp R1 can be used to indirectly address the internal ram and DPTR to indirectly address the external ram The compiler will try to allocate the appropriate register to pointer variables if it can ICode example section shows the operands annotated with the registers assigned to them The compiler will try to keep operands in registers as much as possible there are several schemes the compiler uses to do achieve this When the compiler runs out of registers the compiler will check to see if there are any live operands which is not used or defined in the current basic block 103 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS being processed if there are any found then it will push that operand and use the registers in this block the operand will then be popped at the end of the basic block
47. AST Annotated Syntax Tree This phase also involves propagating types annotating each node of the parse tree with type information and semantic analysis There are some MCU specific parsing rules For example the storage classes the extended storage classes are MCU specific while there may be a xdata storage class for 8051 there is no such storage class for z80 SDCC allows MCU specific storage class extensions 1 e xdata will be treated as a storage class specifier when parsing 8051 C code but will be treated as a C identifier when parsing z80 code Generating iCode Intermediate code generation In this phase the AST is broken down into three operand form iCode These three operand forms are represented as doubly linked lists Code is the term given to the interme diate form generated by the compiler ICode example section shows some examples of Code generated for some simple C source functions Optimizations Bulk of the target independent optimizations is performed in this phase The optimizations in clude constant propagation common sub expression elimination loop invariant code movement strength reduction of loop induction variables and dead code elimination Live range analysis During intermediate code generation phase the compiler assumes the target machine has infinite number of registers and generates a lot of temporary variables The live range computation determines the lifetime of each of these compiler generated temporaries
48. Alan made his ASxxxx Cross Assemblers version 5 0 available under the GPL licence GPLV3 or later so a reunion could be possible Thanks Alan 2 9 4 s51 sz80 shc08 The Simulators s51 sz80 and shc08 are free open source simulators developed by Daniel Drotos The simulators are built as part of the build process For more information visit Daniel s web site at http mazsola iit uni miskolc hu drdani embedded s51 It currently supports the core mcs51 the Dallas DS80C390 the Phillips XA51 family the Z80 and the 6808 2 9 5 sdcdb Source Level Debugger SDCDB is the companion source level debugger More about SDCDB in section 5 1 The current version of the debugger uses Daniel s Simulator S51 but can be easily changed to use other simulators 21 Chapter 3 Using SDCC 3 1 Compiling 3 1 1 Single Source File Projects For single source file 8051 projects the process is very simple Compile your programs with the following command sdcc sourcefile c This will compile assemble and link your source file Output files are as follows sourcefile asm Assembler source file created by the compiler sourcefile lst Assembler listing file created by the Assembler sourcefile rst Assembler listing file updated with linkedit information created by linkage editor sourcefile sym symbol listing for the sourcefile created by the assembler sourcefile rel Object file created by the assembler input to Linkage editor s
49. CC_MODEL_FLAT 24 ds390 59 SDCC_MODEL_LARGE 59 SDCC_MODEL_MEDIUM 59 SDCC_MODEL_SMALL 59 SDCC_PARMS_IN_BANKI 59 SDCC_pic16 67 SDCC_REVISION svn revision number 59 SDCC_STACK_AUTO 59 SDCC_STACK_TENBIT ds390 59 SDCC_USE_XSTACK 59 SDCC_z80 59 Environment variables NO_REG_OPT 66 OPTIMIZE_BITFIELD_POINTER_GET PIC16 66 SDCC_HOME 33 SDCC_INCLUDE 33 SDCC_LEAVE_SIGNALS 33 SDCC_LIB 33 SDCC_PIC14_SPLIT_LOCALS 64 TMP TEMP TMPDIR 33 undocumented 33 SDCC Wiki 89 _sdcc_external_startup 45 sdcclib 24 SDCDB debugger 21 77 84 86 sdcpp preprocessor 21 26 57 sdld 6 84 Search path 13 semaphore 43 sfr 35 37 60 __ sfr 35 37 sfr16 35 __sfr16 35 sfr32 35 __sfr32 35 shc08 simulator 21 signal handler 33 sloc spill location 29 splint syntax checking tool 32 76 86 srecord bin hex tool 22 23 27 86 stack 27 30 34 36 39 41 43 55 92 stack overflow 41 Startup code 44 static 39 Status of documentation 7 18 115 INDEX INDEX Storage class 33 39 55 Strength reduction 92 106 struct 99 Subexpression 93 Subexpression elimination 29 91 Subversion code repository 88 89 Support 88 swapping nibbles bytes 96 switch statement 29 93 95 Symbol listing 22 sz80 simulator 21 tabulator spacing 8 columns 16 Test suite 90 Tinibios DS390 55 TLCS 900H 26 Tools 84 Trademarks 110 type conversion 8 t
50. C_RIGHT IC_RIGHT IC_RESULTO de IC_LEFT Bitwise OR IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULTO BITWISEAND IC_LEFTO Bitwise AND IC_RESULT IC_LEFT amp IC_RIGHT IC_RIGHT IC_RESULTO LEFT_OP IC_LEFTO Left shift IC_RESULT IC_LEFT lt lt IC_RIGHT IC_RIGHT IC_RESULTO RIGHT_OP IC_LEFTO Right shift IC_RESULT IC_LEFT gt gt IC_RIGHT IC_RIGHT IC_RESULTO GET_VALUE_ IC_LEFTO Indirect fetch IC_RESULT IC_LEFT AT_ ADDRESS IC_RESULTO POINTER_SET IC_RIGHT Indirect set IC_RESULT IC_RIGHT IC_RESULTO IC_RIGHT Assignment IC_RESULT IC_RIGHT IC_RESULTO TFX IC_COND Conditional jump If true la if IC_COND goto IC_TRUE IC_TRUE bel is present then jump to true Or IC_LABEL label if condition is true else If IC_COND goto IC_FALSE jump to false label if condition is false ADDRESS_OF IC_LEFT Address of IC_RESULT amp IC_LEFT IC_RESULTO JUMPTABLE IC_JTCOND Jump to list of labels depending Switch statement IC_JTLABELS on the value of JTCOND CAST IC_RIGHT Cast types IC_RESULT typeof IC_LEFT IC_RIGHT IC_LEFT IC_RESULTO SEND IC_LEFTO This is used for passing param None eters in registers move IC_LEFT to the next available parameter register RECV IC_RESULTO This is used for receiving pa None rameters passed in registers Move the values in the next pa rameter register to IC_RESULT 105 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS iCo
51. DCC allows via language extensions pointers to explicitly point to any of the memory spaces of the 8051 In addition to the explicit pointers the compiler uses by default generic pointers which can be used to point to any of the memory spaces Pointer declaration examples x pointer physically in internal ram pointing to object in external ram __xdata unsigned char _ data p pointer physically in external ram pointing to object in internal ram __data unsigned char __xdata p 3Not really meant as examples but nevertheless showing what bitfields are about device include mc68hc908qy h and sup port regression tests bitfields c 35 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC pointer physically in code rom pointing to data in xdata space __xdata unsigned char _ code p pointer physically in code space pointing to data in code space __ code unsigned char _ code p x generic pointer physically located in xdata space x unsigned char __xdata p generic pointer physically located in default memory space x unsigned char p x the following is a function pointer physically located in data space char __data fp void Well you get the idea All unqualified pointers are treated as 3 byte 4 byte for the ds390 generic pointers The highest order byte of the generic pointers contains the data space information Assembler support rou
52. E DIR _SUFFIX sdcc non free include non free include LIB_DIR_SUFFIX sdcc lib lib NON_FREE_LIB_DIR_SUFFIX sdcc non free lib non free lib configure also computes relative paths This is needed for full relocatability of a binary package and to complete search paths see section search paths below Variable computed default Win32 builds BIN2DATA_DIR share x PREFIX2BIN_DIR bin bin PREFIX2DATA_DIR share sdcc 11 2 2 INSTALL PATHS CHAPTER 2 INSTALLING SDCC Examples configure configure prefix usr bin datarootdir usr share configure disable avr port disable xa5l port To cross compile on linux for Mingw32 see also sdcc support scripts sdcc_mingw32 configure CC 1586 mingw32msvc gec CXX 1586 mingw32msvc gt RANLIB i586 mingw32msvc ranlib STRIP 1586 mingw32msvc strip prefix sdcc datarootdir sdcec docdir datarootdir doc include_dir_suffix include non_free_include_dir_suffix non free include lib_dir_suffix lib N non_free_lib_dir_suffix non free lib sdccconf_h_dir_separator disable device lib host i586 mingw32msvc build unknown unknown linux gnu To cross compile on Cygwin for Mingw32 see also sdcc support scripts sdcc_cygwin_mingw32 configure C prefix sdcc datarootdir sdcc docdir datarootdir doc
53. EA 0 or BA SAVE EA EA 0 EA 1 EA EA_SAVE On other architectures which have separate opcodes for enabling and disabling interrupts you might want to make use of defines with inline assembly HC08 define CLI asm cli _ endasm define SEI asm sel endasm Note it is sometimes sufficient to disable only a specific interrupt source like f e a timer or serial interrupt by manipulating an interrupt mask register Usually the time during which interrupts are disabled should be kept as short as possible This minimizes both interrupt latency the time between the occurrence of the interrupt and the execution of the first code in the interrupt 42 3 11 FUNCTIONS USING PRIVATE REGISTER BANKS MCS51 DS390 CHAPTER 3 USING SDCC routine and interrupt jitter the difference between the shortest and the longest interrupt latency These really are something different f e a serial interrupt has to be served before its buffer overruns so it cares for the maximum interrupt latency whereas it does not care about jitter On a loudspeaker driven via a digital to analog converter which is fed by an interrupt a latency of a few milliseconds might be tolerable whereas a much smaller jitter will be very audible You can reenable interrupts within an interrupt routine and on some architectures you can make use of two or more levels of interrupt priorities On some architectures which don t support interrupt priorities
54. EBUGGING if no arg rr rr ii buffer rr P at rr rr 9 buffer jj it off rr pes CHC Gert rr 2y C Ks SPC point wre HOC E ie ESC m ae d sdcdbsrc goto sdcdb sdcdb print c sexp sdcdbsrc goto sdcdb sdcdbsrc mode sdcdb finish from src sdcdb break sdcdbsrc mode sdcdbsrc srcmode 81 given or display frame arg buffer point Goto the SDCDB output SDCDB print command for data buffer point Goto the SDCDB output Toggles Sdcdbsrc mode turns SDCDB finish command Set break for line with Toggle Sdcdbsre mode Toggle list mode Chapter 6 TIPS Here are a few guidelines that will help the compiler generate more efficient code some of the tips are specific to this compiler others are generally good programming practice e Use the smallest data type to represent your data value If it is known in advance that the value is going to be less than 256 then use an unsigned char instead of a short or int Please note that ANSI C requires both signed and unsigned chars to be promoted to signed int before doing any operation This promotion can be omitted if the result is the same The effect of the promotion rules together with the sign extension is often surprising unsigned char uc Oxfe if uc uc lt 0 this is true uc uc is evaluated as int uc int uc int Oxfe x int Oxfe int Oxfc04 1024 Another one unsigned char
55. EO SU CORE kk eR a A AO a Cao AoA A a eS SE 46 Inline Assembler Code cocido Bb See eee a o he eh sd 46 3 13 1 A Step by Step Introduction store s sos ee ee ee ek a 46 CONTENTS CONTENTS 313 2 Naked PUNCIGOS ck e a e Be a a OE bo AS 48 3 13 3 Use of Labels within Inline Assembler nestr 49 3 14 Interfacing with Assembler Code cio lt so socie sedas 50 3 14 1 Global Registers used for Parameter Passing 50 Sls RESISTIR USABE 22 a s e si eae Sa eet eae as 50 3 14 3 Assembler Routine non Teentradt s spes earen dp eeka endhih 50 3 14 4 Assembler Routine reentrant aooaa ee 51 3 13 ft 16 bit and long 32 Dit SUpport lt e seos a a eR a RS Se Oe eee 52 gt 10 Hosting Paint SUppoel e ed ok ir RES oe ee AAA 52 ALP Library ROUNDS ooo cor Sak Pad Re OR AR bee Be OO 53 3 17 1 Compiler support routines _gptrget __mulintetc o 53 3 17 2 Stdclib functions puts printf streat ete s sos se so a soca se a 53 SEP od SIGN ee a a Ree MAS a e e ae be a e aS 53 A ARNE a SS See se BE A SG a ae Re Ree ee SS 54 3 17 3 Math functions sinf powf sqrtfetc o o e 54 E A AN 54 SITA id A A 54 2 Le Menor Modele oie otis BMS Eee dt Le eae a aha Gie Bee Od ee Seg 55 318 1 MCSS1 Memory Models ce ee ee eR ER RE ER BES 55 3 18 1 1 Small Medium Large and Huge 55 3181 2 Extem
56. K name with ECTE The linker will recognise the section name set in the pragma statement and will position the variable at the memory bank set with the RAM field at the SECTION line in the linker script file 68 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 7 Header Files and Libraries Pic device specific header and c source files are automatically generated from MPLAB include files which are published by Microchip with a special requirement that they are only to be used with authentic Microchip devices This requirement prevents to publish generated header and c source files under the GPL compatible license so they are located in the non free directory see section 2 3 In order to include them in include and library search paths the use non free command line option should be defined NOTE the compiled code which use non free pic device specific libraries is not GPL compatible 4 6 8 Header Files There is one main header file that can be included to the source files using the picl6 port That file is the picl8fregs h This header file contains the definitions for the processor special registers so it is necessary if the source accesses them It can be included by adding the following line in the beginning of the file include lt picl8fregs h gt The specific microcontroller is selected within the pic18fregs h automatically so the same source can be used with a variety of devices 4 6 9
57. Libraries The libraries that PIC16 port depends on are the microcontroller device libraries which contain the symbol defini tions for the microcontroller special function registers These libraries have the format pic18fxxxx lib where xxxx is the microcontroller identification number The specific library is selected automatically by the compiler at link stage according to the selected device Libraries are created with gplib which is part of the gputils package http sourceforge net projects gp tils Building the libraries Before using SDCC pic16 there are some libraries that need to be compiled This process is done automatically if gputils are found at SDCC s compile time Should you require to rebuild the pic16 libraries manually e g in order to enable output of float values via printf see below these are the steps required to do so under Linux or Mac OS X cygwin might work as well but is untested cd device lib picl6 configure gnu ole 3 make model picl6 su c make install install the libraries you need the root password Cd wifes If you need to install the headers too do cd device include su c make install install the headers you need the root password Output of float values via printf The library is normally built without support for displaying float values only lt NO FLOAT gt will appear instead of the value To change this rebuild the library as stated above but call confi
58. Oxff mov r0 a _gint lr0 0 int _gint Ir0 0 int iTemp17 Ir23 38 int 17 r0 mov a r7 108 9 2 A FEW WORDS ABOUT BASIC BLOCK SUCCESSORS PREDEMABSOR Y ASNONIOMERNANORRNALS add a _gint mov _gint a mov a r0 addc a _gint 1 mov _gint 1 a iTemp21 1r21 38 short r4 iTemp21 lr21 38 short r4 0x1 short inc r4 iTemp23 lr22 38 int r5 r6 iTemp23 Ir22 38 int r5 r6 0x1 short dec r5 cjne 15 0xff 00104 dec r6 goto _forcond_0 4 sjmp 00104 forbreak_0 7 00107 ret Temp24 lr40 41 short mov a r3 add a r2 mov dpl a _return 8 00108 ret 9 2 A few words about basic block successors predecessors and domina tors Successors are basic blocks that might execute after this basic block Predecessors are basic blocks that might execute before reaching this basic block Dominators are basic blocks that WILL execute before reaching this basic block basic block 1 if something basic block 2 else basic block 3 basic block 4 a succList of BB2 BB4 of BB3 BB4 of BB1 BB2 BB3 b predList of BB2 BB1 of BB3 BB1 of BB4 BB2 BB3 c domVect of BB4 BB here we are not sure if BB2 or BB3 was executed but we are SURE that BB1 was executed 109 Chapter 10 Acknowledgments http sdcc sourceforge net Who Thanks to all the other volunteer developers who have helped with coding testing web page creation dis
59. R 71 x 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 14 Function return values Return values from functions are placed to the appropriate registers following a modified Microchip policy opti mized for SDCC The following table shows these registers size destination register 8 bits WREG 16 bits PRODL WREG 24 bits PRODH PRODL WREG 32 bits FSROL PRODH PRODL WREG gt 32 bits on stack FSRO points to the beginning 4 6 15 Interrupts An interrupt service routine ISR is declared using the interrupt keyword void isr void interrupt n n is the interrupt number which for PIC18F devices can be n Interrupt Vector Interrupt Vector Address 0 RESET vector 0x000000 1 HIGH priority interrupts 0x000008 2 LOW priority interrupts 0x000018 When generating assembly code for ISR the code generator places a GOTO instruction at the Interrupt Vector Address which points at the generated ISR This single GOTO instruction is part of an automatically generated interrupt entry point function The actuall ISR code is placed as normally would in the code space Upon interrupt request the GOTO instruction is executed which jumps to the ISR code When declaring interrupt functions as _naked this GOTO instruction is not generated The whole interrupt functions is therefore placed at the Interrupt Vector Address of the specific interrupt This is not
60. SDCC Compiler User Guide SDCC 3 0 0 Date 2010 10 19 Revision 6035 Contents 1 Introduction LI ABGIESDOS socia a A Ge EE a a aw a A a e OA 12 OPUSME ces ad E A Y a doe la de 13 Typographic convennans s es s e ia AA eS RARE RS ES 14 Compatibility with previ s Versions 29 se ss AR RR LA SNS RS QUIEMBIS sec cess AS Se ee he A a s Lo Aer Resonis sos od Gee e Gb wee ae A A ad aol ee de os LF Wishes forihe TUE score 488446 a A A eee a 2 Installing SDCC 21 Conies OUPIODS s sy asa RE A EE Bas a A Doe MRS PS lt lt rd Pe eee do ee ea ee ee eee a ed e Gein PAINS ono PA GRA ERE EEE EE Ge EASES Sede OHA i 2A a oe cae ak e Aa RS Oe ee ORR ER ae wa RG Se ee aLI Blame sDCC en LIME secos hed be RS eG ee RS BB See Se Ba s 22 Bulma DC on MacOS XA oscar ee RE EERE RRP OEE Oe eee EO 2 4 3 Cross compiling SDCC on Linux for Windows 2 4 4 Building SDCC using Cygwin and Mingw32 2 4 5 Building SDCC Using Microsoft Visual C 6 0 NET MSVC 2 4 6 Windows Install Using a ZIP Package gt o o 2 ee eee ee ee 2 4 7 Windows Install Using the Setup Program ee ee 24 6 WRATH ICIMIS e e e e Eee eed eh a N zo Building the Documentanen sps 6 4 ky oe a pe A a Re RO 2 Reading the Documentation lt s s Axe Reed be Roe a e e BA eee ee Ba a 27 Teste he SDC Compiler gs see Pas es ee PL eR ERR PERE AS se He ee 2 Install Troubleshooting s colors e
61. T Pop the operand from the stack NONE CALL IC_LEFTO Call the function represented IC_RESULT IC_LEFT IC_RESULT by IC_LEFT PCALL IC_LEFTO Call via function pointer IC_RESULT IC_LEFT IC_RESULT RETURN IC_LEFTO Return the value in operand return IC_LEFT IC_LEFT LABEL IC_LABEL Label IC_LABEL GOTO IC_LABEL Goto label goto IC_LABELO Y IC_LEFT Addition IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULT gt IC_LEFT Subtraction IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULT neo IC_LEFT Multiplication IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULT P IC_LEFT Division IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULT gt IC_LEFT Modulus IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULT 2 IC_LEFT Less than IC_RESULT IC_LEFT lt IC_RIGHT IC_RIGHT IC_RESULT 104 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS Code Operands Description C Equivalent gt IC_LEFT Greater than IC_RESULT IC_LEFT gt IC_RIGHT IC_RIGHT IC_RESULTO EQ_OP IC_LEFTO Equal to IC_RESULT IC_LEFT IC_RIGHT IC_RIGHT IC_RESULTO AND_OP IC_LEFT Logical and operation IC_RESULT IC_LEFT amp amp IC_RIGHT IC_RIGHT IC_RESULTO OR_OP IC_LEFT Logical or operation IC_RESULT IC_LEFT Il IC_RIGHT IC_RIGHT IC_RESULTO IN IC_LEFT Exclusive OR IC_RESULT IC_LEFT I
62. There are other MCU specific considerations in this phase Some MCUs have an accumulator very short lived operands could be assigned to the accumulator instead of a general purpose register Code generation Figure II gives a table of iCode operations supported by the compiler The code generation involves translating these operations into corresponding assembly code for the processor This sounds overly simple but that is the essence of code generation Some of the iCode operations are generated on a MCU specific manner for example the z80 port does not use registers to pass parameters so the SEND and RECV iCode operations will not be generated and it also does not support JUMPTABLES Figure II Code Operands Description C Equivalent Bl IC_LEFT NOT operation IC_RESULT IC_LEFT IC_RESULT gt IC_LEFTO Bitwise complement of IC_RESULT IC_LEFT IC_RESULT RRC IC_LEFT Rotate right with carry IC_RESULT IC_LEFT lt lt 1 IC_LEFT gt gt IC_RESULT sizeof IC_LEFT 8 1 RLC IC_LEFT Rotate left with carry IC_RESULT IC_LEFT lt lt sizeof LC_LEFT 8 1 IC_RESULT IC_LEFT gt gt 1 GETHBIT IC_LEFT Get the highest order bit of IC_RESULT IC_LEFT gt gt sizeof IC_LEFT 8 1 IC_RESULT IC_LEFT UNARYMINUS IC_LEFT Unary minus IC_RESULT IC_LEFT IC_RESULT IPUSH IC_LEFT Push the operand into stack NONE IPOP IC_LEF
63. U is not available search for Software UART in your favourite search machine use an on target monitor In this context a monitor is a small program which usually accepts commands via a serial line and allows to set program counter to single step through a program and read write memory locations For the 8051 good examples of monitors are paulmon and cmon51 see section 6 5 toggle MCU port pins at strategic points within your code and use an oscilloscope A digital oscilloscope with deep trace memory is really helpful especially if you have to debug a realtime application If you need to monitor more pins than your oscilloscope provides you can sometimes get away with a small R 2R network On a single channel oscilloscope you could for example monitor 2 push pull driven pins by connecting one via a 10 kQ resistor and the other one by a 5 kQ resistor to the oscilloscope probe check output drive capability of the pins you want to monitor If you need to monitor many more pins a logic analyzer will be handy use an ICE in circuit emulator Usually very expensive And very nice to have too And usually locks you for years to the devices the ICE can emulate 76 5 1 DEBUGGING WITH SDCDB CHAPTER 5 DEBUGGING e use a remote debugger In most 8 bit systems the symbol information is not available on the target and a complete debugger is too bulky for the target system Therefore usually a debugger on the host system con nects to an on ta
64. UNE cr 08450 eee pe be bbe eee eae be ee aes 27 S28 MESIN OPRONS si etd eee hess be baw Be ed de eae Sa eet eae as 27 A E A bes ws poe ae eS aes bE Se es 28 J APRA tk oe ChE EES eRe e dd S 29 2l E e e ia es Ba Re he we GA Ae es Sew Sa Re 29 326 CPI ORO PUGNG os AN oe Bodhi eee eg elo oe wk OE ede ie Sages 29 329 Mc PHONG ee cg GN PA OR eR ee ee ee ER SY e Be Oe 30 3 2 10 Intermediate Dump Options 6644 50844 eee ee ee ee eee 32 3 2 11 Redirecting output on Windows Shells e 33 Environment VAciables s seso ers AA 33 Storage Class Language BXIensiOAS c oc socre os erona panoan a eR eS 33 3 4 1 MCS51 DS390 Storage Class Language Extensions 33 A CMP RAY AN 33 JALEA AAA cr a ee EO Shape e a a ee 34 E E A O ets Bees 34 SALA AN 34 SA E O e A ESA a A O A oes 34 E DE cs ced A Bhs Berek E at thd be be eB 35 IALT A MA 35 3 4 1 8 Pointers to MCS51 DS390 specific memory spaces 35 3 4 1 9 Notes on MCS51 memory layout o o 36 3 4 2 Z80 Z180 Storage Class Language Extensions 37 3 4 2 1 sfr in out to 8 bit addresses e o eo 37 3 4 2 2 banked sfr in out to 16 bit addresses 02 00000000 37 3 4 2 3 sfr in0 out0 to 8 bit addresses on Z180 HD64180 37 3 4 3 HC08 Storage Class Language Extensions e 37 SAL CA o e A A ER A Eee e Res 37 Sete A NN 37 Ot
65. a problem for the LOW priority interrupts but it is a problem for the RESET and the HIGH priority interrupts because code may be written at the next interrupt s vector address and cause indeterminate program behaviour if that interrupt is raised n may be omitted This way a function is generated similar to an ISR but it is not assigned to any interrupt When entering an interrupt currently the PIC16 port automatically saves the following registers e WREG e STATUS e BSR e PROD PRODL and PRODH e FSRO FSROL and FSROH These registers are restored upon return from the interrupt routine 3This is not a problem when 1 this is a HIGH interrupt ISR and LOW interrupts are disabled or not used 2 when the ISR is small enough not to reach the next interrupt s vector address 4NOTE that when the _naked attribute is specified for an interrupt routine then NO registers are stored or restored 72 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 16 Generic Pointers Generic pointers are implemented in PIC16 port as 3 byte 24 bit types There are 3 types of generic pointers currently implemented data code and eeprom pointers They are differentiated by the value of the 7th and 6th bits of the upper byte pointer type 7th bit 6th bit rest of the pointer description data 1 0 uuuuuu UUUUXXXX XXXXXXXX a 12 bit data pointer in data RAM memory code 0 0 UXXXXX XXXXXXXX XXXXXXXX a 21 bit co
66. al Stack ius bss aa eh eb ke eS 55 3 18 2 DS390 Memory Model gt lt se ee ee ee ee ee ee ee 55 So PRBS sae ek a A A RG ee A OE ls be Re Bae eS BGA S 55 3 20 Defines Created by the Compiler e oe eh ee a a ee E 59 4 Notes on supported Processors 60 SL ME oT PANO a ae SG EAS eS Be ee we eee Eee ew SS 60 AII piletanceess by SPR nk e em rd EE ee be O el ee eS 60 4 12 Other Features available by SFR e c 26045 2554 494454 2455 S240 4 oe oS 60 RAI gt DADES UCI ces a Ok ee ee EE RES A ee OE ee 60 4 1 3 1 Hawa 6 405404 484404 baa Ee ea ee Hee ee eG we es 61 AL Z SOWIE lt a RG RR AS BR a RS 61 42 DS400 MOM rce ie o hee ee hea Oe a PR owe ee 61 4 3 TheZ band COz80 port o ecos sr more saaa a ee a a a ee a 61 44 Whe HOUS pom 6444554482640 2 Oe Be ee Se eee A a eS 62 Aor EPPO 22022 or EMA SLES e eee Le eae edie caw ad 62 45 1 PIC Code Pages and Memory Banks 1 6 25 eee e Ep eee eS 62 452 Adding New Devices to the Ports 26 9 255k A is 63 ASS Intetapelode lt p a i Bre E e GAS Shoe a Oe eS 63 ASA ELiokme and Assembling cs ira silos ede ee POE Bee ORES Yee Saws 63 435 Uormand Line OPUS lt ao 4 ae ee A eS a 64 45 6 Environment Variables 6245 ee ee ee bw ee eee 64 AST The LIMAN pose mi Ae a a ele Sh a ee a 64 4 5 7 1 error missing definition for symbol __gptrgetl 64 4 5 7 2 Processor mismatch in file XXX recre some seas 64 45 8 Known Bugg roc rerea 0404 608R 4b bea ow E bea wee E Ge
67. ameter will be _ lt function_name gt _PARM_2 Assemble the assembler routine with the following command sdas8051 losg asmfunc asm Then compile and link the assembler routine to the C source file with the following command sdcc cfunc c asmfunc rel 3 14 4 Assembler Routine reentrant In this case the second parameter onwards will be passed on the stack the parameters are pushed from right to left i e before the call the second leftmost parameter will be on the top of the stack the leftmost parameter is passed in registers Here is an example extern int asm_func unsigned char unsigned char unsigned char reentrant int c_func unsigned char i unsigned char j unsigned char k reentrant return asm_func i j k int main return c_func 10 9 8 The corresponding unoptimized assembler routine is globl _asm_func _asm_func push _bp mov _bp sp stack contains _bp return address second parameter third parameter mov r2 dpl mov a _bp add a 0xfd calculate pointer to the second parameter mov r0 a mov a _bp add a t0xfc calculate pointer to the rightmost parameter mov rl a mov a r0 add a rl add a r2 calculate the result sum of all three parameters mov dpl a return value goes into dptr cast into int mov dph 0x00 mov sp _bp pop _bp ret The compiling and linking procedure remains the same however note the extra entry amp exit linkage required for the asse
68. bit loc lt Value gt The start location of the bit addressable internal ram of the 8051 This is not implemented yet Instead an option can be passed directly to the linker W1 bBSEG lt Value gt out fmt ihx The linker output final object code is in Intel Hex format This is the default option The format itself is documented in the documentation of srecord out fmt s19 The linker output final object code is in Motorola 19 format The format itself is documented in the documentation of srecord out fmt elf The linker output final object code is in ELF format Currently only supported for the HC08 processors WI linkOption linkOption Pass the linkOption to the linker If a bootloader is used an option like W1 bCSEG 0x 1000 would be typical to set the start of the code segment Either use the double quotes around this option or use no space e g WI bCSEG 0x1000 See also pragma constseg and pragma codeseg in section3 19 File sdcc sdas doc asxhtm html has more on linker options 3 2 4 MCS51 Options model small Generate code for Small model programs see section Memory Models for more details This is the default model 27 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC model medium Generate code for Medium model programs see section Memory Models for more details If this option is used all source files in the project have to be compiled with this option It must also be used when invoking the l
69. c include picl PIC16 specific headers Compiler I PREFIX sdcc lib pic16 PIC16 specific libraries Linker L If the use non free commad line option is specified non free diractories are searched Directory Description Target Command prefix PREFIX sdcc non free include pic16 PIC16 specific non free headers Compiler I PREFIX sdcc non free lib pic16 PIC16 specific non free libraries Linker L 4 6 6 Pragmas The PIC16 port currently supports the following pragmas stack This forces the code generator to initialize the stack amp frame pointers at a specific address This is an ad hoc solution for cases where no STACK directive is available in the linker script or gplink is not instructed to create a stack section The stack pragma should be used only once in a project Multiple pragmas may result in indeterminate behaviour of the program The format is as follows pragma stack bottom_address stack_size bottom_address is the lower bound of the stack section The stack pointer initially will point at address bottom_address stack_size 1 Example x initializes stack of 100 bytes at RAM address 0x200 x pragma stack 0x200 100 If the stack_size field is omitted then a stack is created with the default size of 64 This size might be enough for most programs but its not enough for operations with deep function nesting or excessive stack usage The old format ie pragma stack Ox5ff is
70. cation will take place and overlaps will be detected by the linker E g _ code __at 0x7ff0 char Id 5 SDCC In the above example the variable Id will be located from 0x7ff0 to 0x7ff4 in code memory In case of memory mapped I O devices the keyword volatile has to be used to tell the compiler that accesses might not be removed volatile __xdata __at 0x8000 unsigned char PORTA_8255 For some architectures mcs51 array accesses are more efficient if an xdata far array starts at a block 256 byte boundary section 3 13 1 has an example Absolute addresses can be specified for variables in all storage classes e g bit __at 0x02 bvar The above example will allocate the variable at offset 0x02 in the bit addressable space There is no real advantage to assigning absolute addresses to variables in this manner unless you want strict control over all the variables allocated One possible use would be to write hardware portable code For example if you have a routine that uses one or more of the microcontroller I O pins and such pins are different for two different hardwares you can declare the I O pins in your routine using extern volatile _ bit MOSI master out slave in x extern volatile _ bit MISO master in slave out x extern volatile _ bit MCLK master clock x x Input and Output of a byte on a 3 wire serial bus If needed adapt polarity of clock polarity of data and bit order unsig
71. check whether endianness of the compilers differs and adapt where needed check the device specific header files for compiler specific syntax Eventually include the file lt compiler h gt http sdcc svn sourceforge net viewvc sdcc trunk sdcc device include mes51 compiler h view markup to allow using common header files see fe cc2510fx h http sdcc svn sourceforge net viewvc sdcc trunk sdcc device include mcs51 cc2510fx h view markup check whether the startup code contains the correct initialization watchdog peripherals check whether the sizes of short int long match check if some 16 or 32 bit hardware registers require a specific addressing order least significant or most significant byte first and adapt if needed first and last relate to time and not to lower upper memory location here so this is not the same as endianness check whether the keyword volatile is used where needed The compilers might differ in their optimization characteristics as different versions of the same compiler might also use more clever optimizations this is good idea anyway See section 3 9 1 1 check that the compilers are not told to suppress warnings check and convert compiler specific extensions interrupts memory areas pragmas etc check for differences in type promotion Especially check for math operations on char or unsigned char variables For the sake of C99 compatibility SDCC will probably promote these to int more often
72. cky someone already had a similar problem While mails to the lists themselves are delivered promptly their web front end on sourceforge sometimes shows a severe time lag up to several weeks 1f you re seriously using SDCC please consider subscribing to the lists 7 5 ChangeLog You can follow the status of the Subversion version of SDCC by watching the Changelog in the Subversion reposi tory http sdcc svn sourceforge net viewcvs cgi checkout sdcc trunk sdcc ChangeLog 7 6 Subversion Source Code Repository The output of sdcc version or the filenames of the snapshot versions of SDCC include date and its Subversion number Subversion allows to download the source of recent or previous versions http sourceforge net svn group_id 599 by number or by date An on line source code browser and detailled instructions are also available there SDCC versions starting from 1999 up to now are available currently the versions prior to the conversion from cvs to Subversion April 2006 are either by accessible by Subversion or by cvs 7 7 Release policy Historically there often were long delays between official releases and the sourceforge download area tended to get not updated at all Starting with version 2 4 0 SDCC in 2004 switched to a time based release schedule with one official release usually during the first half of the year The last digit of an official release is zero Additionally there are daily snapshots available at snap http
73. cl8fregs h The file format is self explanatory just add elif defined picDEVICE include lt picDEVICE h gt at the right place keep the file sorted please 7 Edit path to sdcc device include picl devices txt Copy and modify an existing entry or create a new one and insert it at the correct place keep the file sorted please 8 Add the device to path to sdcc device lib pic16 libdev Makefile am Copy an existing entry and adjust the device name 9 Add the device to path to sdcc device lib picl6 libio Makefile am Copy the record from the 18 2220 and adjust the device name If the new device does not offer ADC I2C and or EJUSART functionality as assumed by the library or if you added the new device to libio adc i2c usart ignore remove the lines with references to adc c i2c c or usart c respectively 10 Update libdev Makefile inand libio Makefile in using bootstrap sh in path to sdcc device lib picl6 11 Recompile the pic16 libraries as described in 4 6 9 4 6 11 Memory Models The following memory models are supported by the PIC16 port e small model e large model Memory model affects the default size of pointers within the source The sizes are shown in the next table 2In fact the ignore files are only used when auto generating Makefile am from steps 8f using the 1ibio mkmk sh script to actually suppress building the I O library you m
74. complete tests The test code might also be interesting if you want to look for examples checking corner cases of SDCC or if you plan to submit patches The PIC14 port uses a different set of regression tests you ll find them in the directory sdcc src regression 7 9 Examples You 1l find some small examples in the directory sdcc device examples More examples and libraries are avail able at The SDCC Open Knowledge Resource http sdccokr dl9sec de web site or at http www pjrc com tech 8051 7 10 Use of SDCC in Education In short highly encouraged If your rationales are to 1 give students a chance to understand the complete steps of code generation 2 have a curriculum that can be extended for years Then you could use an fpga board as target and your cur riculum will seamlessly extend from logic synthesis http www opencores org opencores org Oregano http www oregano at ip ip01 htm over assembly programming to C to FPGA compilers FPGAC http sf net projects fpgac and to C 3 be able to insert excursions about skills like using a revision control system submitting applying patches using a type setting as opposed to word processing engine LyX I4T X using SourceForge http www sf net following some netiquette http en wikipedia org wiki Netiquette understand ing BSD LGPL GPL Proprietary licensing growth models of Open Source Software CPU simulation com piler regression tests And if there shoul
75. convert Intel Hex file to a binary and GameBoy binary image file format In lt installdir gt share sdcc include e the include files In lt installdir gt share sdcc non free include e the non free include files In lt installdir gt share sdcc lib e the src and target subdirectories with the precompiled relocatables In lt installdir gt share sdcc non free lib e the src and target subdirectories with the non free precompiled relocatables In lt installdir gt share sdcc doc e the documentation 20 2 9 COMPONENTS OF SDCC CHAPTER 2 INSTALLING SDCC 2 9 1 sdcc The Compiler This is the actual compiler it in turn uses the c preprocessor and invokes the assembler and linkage editor 2 9 2 sdcpp The C Preprocessor The preprocessor is a modified version of the GNU cpp preprocessor http gcc gnu org The C prepro cessor is used to pull in include sources process ifdef statements defines and so on 2 9 3 sdas sdld The Assemblers and Linkage Editors This is a set of retargettable assemblers and linkage editors which was developed by Alan Baldwin John Hartman created the version for 8051 and I Sandeep have made some enhancements and bug fixes for it to work properly with SDCC SDCC uses an about 1998 branch of asxxxx version 2 0 which unfortunately is not compatible with the more advanced f e macros more targets ASxxxx Cross Assemblers nowadays available from Alan Baldwin http shop pdp kent edu In 2009
76. cuss SDCC with other SDCC users Web links to other SDCC related sites can also be found here This document can be found in the DOC directory of the source package as a text or HTML file A pdf version of this document is available at http sdcc sourceforge net doc sdccman pdf Some of the other tools simulator and assembler included with SDCC contain their own documentation and can be found in the source distribution If you want the latest unreleased software the complete source package is available directly from Subversion on https sdcc svn sourceforge net svnroot sdcc trunk sdcc 1 7 Wishes for the future There are and always will be some things that could be done Here are some I can think of char KernelFunction3 char p at 0x340 better code banking support for mcs51 If you can think of some more please see the section 7 2 about filing feature requests Chapter 2 Installing SDCC For most users it is sufficient to skip to either section 2 4 1 Unix or section 2 4 7 Windows More detailed instructions follow below 2 1 Configure Options The install paths search paths and other options are defined when running configure The defaults can be over ridden by prefix see table below exec_prefix see table below bindir see table below datadir see table below datarootdir see table below docdir environment variable see table below include _dir_suffix environment variable see table below non_free_i
77. d be a shortage of ideas then you can always point students to the ever growing feature request list http sourceforge net tracker group_id 599 amp atid 350599 4 not tie students to a specific host platform and instead allow them to use a host platform of their choice among them Alpha 1386 1386_64 Mac OS X Mips Sparc Windows and eventually OLPC http www laptop org not encourage students to use illegal copies of educational software be immune to licensing availability price changes of the chosen tool chain be able to change to a new target platform without having to adopt a new tool chain have complete control over and insight into the tool chain NO 0 N Dn MN make your students aware about the pros and cons of open source software development 10 give back to the public as you are probably at least partially publicly funded 11 give students a chance to publicly prove their skills and to possibly see a world wide impact then SDCC is probably among the first choices Well probably SDCC might be the only choice 3the phrase use in education might evoke the association only fit for use in education This connotation is not intended but nevertheless risked as the licensing of SDCC makes it difficult to offer educational discounts 90 Chapter 8 SDCC Technical Data 8 1 Optimizations SDCC performs a host of standard optimizations in addition to some MCU specific optimizations 8 1 1 Sub expression Elimi
78. data variables with kword Valid keywords are udata_acs udata_shr udata_ovr ivt loc n Place the interrupt vector table at address n Useful for bootloaders nodefaultlibs Do not link default libraries when linking use crt Use a custom run time module instead of the defaults no crt Don t link the default run time modules 4 6 2 5 Debugging Options Debugging options enable extra debugging information in the output files debug xtra Similar to debug but dumps more information debug ralloc Force register allocator to dump lt source gt d file with debugging information lt source gt is the name of the file being compiled pcode verbose Enable pcode debugging information in translation calltree Dump call tree in calltree file gstack Trace push pops for stack pointer overflow 4 6 3 Environment Variables There is a number of environmental variables that can be used when running SDCC to enable certain optimiza tions or force a specific program behaviour these variables are primarily for debugging purposes so they can be enabled disabled at will Currently there is only two such variables available OPTIMIZE_BITFIELD_POINTER_GET When this variable exists reading of structure bitfields is optimized by directly loading FSRO with the address of the bitfield structure Normally SDCC will cast the bitfield structure to a bitfield pointer and then load FSRO This step saves data ram and code space for fu
79. de Operands Description C Equivalent some more have see f e gen51Code in src mcs51 gen c been added ICode Example This section shows some details of iCode The example C code does not do anything useful it 1s used as an example to illustrate the intermediate code generated by the compiler 1 _xdata int p 2 int gint 3 This function does nothing useful It is used 4 for the purpose of explaining iCode x 5 short function __data int xx 6 1 TA short i 10 x dead initialization eliminated 8 short sum 10 dead initialization eliminated x Ox short mul LO vane yy 11 while x x x ptt LD sum 0 13 mul 0 14 x compiler detects i j to be induction variables VS FOR a i S04 3 gt Or A AA ep of 16 sum i A Be mul i 3 x this multiplication remains x 18 gint j x 3 x this multiplication changed to addition x 19 3 20 return sum mul 21 43 In addition to the operands each iCode contains information about the filename and line it corresponds to in the source file The first field in the listing should be interpreted as follows Filename linenumber iCode Execution sequence number ICode hash table key loop depth of the iCode Then follows the human readable form of the Code operation Each operand of this triplet form can be of three basic types a compiler generated temporary b user defined variable c a con
80. de pointer in FLASH memory eeprom 0 1 uuuuuu uuuuuuxx XXXXXXXX a 10 bit eeprom pointer in EEPROM memory unimplemented 1 1 XXXXXX XXXXXXXX XXXXXXXX unimplemented pointer type Generic pointer are read and written with a set of library functions which read write 1 2 3 4 bytes 4 6 17 PIC16 C Libraries 4 6 17 1 Standard I O Streams In the stdio h the type FILE is defined as typedef char x FILE This type is the stream type implemented I O in the PIC18F devices Also the standard input and output streams are declared in stdio h extern FI extern FI E stdin E stdout The FILE type is actually a generic pointer which defines one more type of generic pointers the stream pointer This new type has the format pointer type lt 7 6 gt lt 5 gt lt 4 gt lt 3 0 gt rest of the pointer descrption stream 00 1 0 nnonn uuuuuuuu uuuuuuuu upper byte high nubble is 0x2n the rest are zeroes Currently implemented there are 3 types of streams defined stream type value module description STREAM_USART 0x200000UL USART Writes Reads characters via the USART peripheral STREAM_MSSP 0x210000UL MSSP Writes Reads characters via the MSSP peripheral STREAM_USER 0x2f0000UL none Writes Reads characters via used defined functions The stream identifiers are declared as macros in the stdio h header In th
81. ding on the hardware implementation Therefore SDCC ignores the optional interrupt number and does not attempt to generate an interrupt vector table By default SDCC generates code for a maskable interrupt which uses a RETI instruction to return from the interrupt To write an interrupt handler for the non maskable interrupt which needs a RETN instruction instead add the critical keyword void nmi_isr void critical interrupt However if you need to create a non interruptable interrupt service routine you would also require the critical keyword To distinguish between this and an nmi_isr you must provide an interrupt number 3 10 Enabling and Disabling Interrupts 3 10 1 Critical Functions and Critical Statements A special keyword may be associated with a block or a function declaring it as critical SDCC will generate code to disable all interrupts upon entry to a critical function and restore the interrupt enable to the previous state before returning Nesting critical functions will need one additional byte on the stack for each call int foo _ critical The critical attribute maybe used with other attributes like reentrant The keyword critical may also be used to disable interrupts more locally _ criticalf i More than one statement could have been included in the block 3 10 2 Enabling and Disabling Interrupts directly Interrupts can also be disabled and enabled directly 8051
82. e 105 case 106 case 107 94 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA then both the switch statements will be implemented using jump tables whereas the unmodified switch statement will not be The pragma nojtbound can be used to turn off checking the jump table boundaries It has no effect if a default label is supplied Use of this pragma is dangerous if the switch argument is not matched by a case statement the processor will happily jump into Nirvana 8 1 8 Bit shifting Operations Bit shifting is one of the most frequently used operation in embedded programming SDCC tries to implement bit shift operations in the most efficient way possible e g unsigned char i i gt gt 4 generates the following code mov a _i swap a anl a 0x0f mov _i a In general SDCC will never setup a loop if the shift count is known Another example unsigned int i i gt gt 9 will generate mov a _i 1 mov _i 1 0x00 clr c rre a mov _i a 8 1 9 Bit rotation A special case of the bit shift operation is bit rotation SDCC recognizes the following expression to be a left bit rotation unsigned char 1 x unsigned is needed for rotation x i 1 lt lt 1 1 gt gt 7 will generate the following code mov a _i El a mov ipa SDCC uses pattern matching on the parse tree to determine this operation Variations of this case will also be recognized as bit rotation 1 e i
83. e A Ca ee el AA 73 AGI WSU Labranes scios doce Aue doa a BS A RRR ae ee Ae Ba A Bs 73 4617 1 Standard VO Streams 5 544 4 44 5606s bow a wea eee had 73 4617 2 Printing FUNCHONS o lt a s eae ken BES ee eee Ge eS 74 A DOTES a e a ew a oe SS 74 46 18 PICIO Port Tips ocins rs nan a AER Se Hewes 75 AOL SBE SIZE ora a RR GOR a OR E OES 75 4 6 19 Known Buss lt c o ecb a e e a a SMO a a A a 75 4 6 19 1 Extended Instruction Set ee 75 46192 Regression TESS ici E e e e a ee ee eR eS AS 75 5 Debugging 76 SL Debuzeme wihSDCODB caso dra e de T SLI Compiling tor Debul sE ss sue ds E a E AR RO 71 si How the Debugger WAKS lt e cocido e A a e W S 77 S13 Sarons the Debugger SDCDB os ud pe ee a oS 77 5 1 4 SDCDB Command Line Options escocesa SERS Eee 78 SLI SDCDB Debugger Commands lt ce ces spes Ae A ew OS Oe 78 5 1 6 Interfacing SDCDB wthDDD 80 517 Interfacing SDCDB With XEMACS 22g ck ee OG a 80 6 TIPS 82 6 1 Portme code irom or ba othercompilers 0064 6 6 ee ee eS ERR OE ae a 83 6 2 Tools included In the distribution lt 4 ceae ss SHR Re eR Le eee S 84 6 3 Documentation included in the distribution 0 0 0 0 0 eee eee 84 64 Communication online at SourceForge cocos rr ee eee 85 6 3 Related Gpen source tools ms cs Ee KE ROR RSE AO OR RR 85 6 6 Related documentation recommended reading e 86 6 7 Application notes specifically forSDCC ow seor ee mae 86
84. e directories See sections 2 2 2 3 about install and search paths On most systems you will need super user privileges to do this 2 9 Components of SDCC SDCC is not just a compiler but a collection of tools by various developers These include linkers assemblers simulators and other components Here is a summary of some of the components Note that the included simulator and assembler have separate documentation which you can find in the source package in their respective directories As SDCC grows to include support for other processors other packages from various developers are included and may have their own sets of documentation You might want to look at the files which are installed in lt installdir gt At the time of this writing we find the following programs for gcc builds In lt installdir gt bin e sdcc The compiler e sdcpp The C preprocessor e sdas8051 The assembler for 8051 type processors e sdasz80 sdasgb The Z80 and GameBoy Z80 assemblers sdas6808 The 6808 assembler e sdld The linker for 8051 type processors sdldz80 sdldgb The Z80 and GameBoy Z80 linkers sd1d6808 The 6808 linker e s51 The ucSim 8051 simulator e sz80 The ucSim Z80 simulator e shc08 The ucSim 6808 simulator e sdcdb The source debugger sdcclib A tool for creating sdcc libraries e asranlib A tool for indexing sdcc ar libraries e packihx A tool to pack compress Intel hex files e makebin A tool to
85. e downloaded from http sdcc sourceforge net snap php Please note the compiler will probably always be some steps ahead of this documentation 1 2 Open Source All packages used in this compiler system are free open source source code for all the sub packages pre processor assemblers linkers etc is distributed with the package This documentation is maintained using a free open source word processor LyX This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 2 or at your option any later version This program is distributed in the hope that 1t will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along with this program if not write to the Free Software Foundation 39 Temple Place Suite 330 Boston MA 02111 1307 USA In other words you are welcome to use share and improve this program You are forbidden to forbid anyone else to use share and improve what you give them Help stamp out software hoarding 1 3 Typographic conventions Throughout this manual we will use the following convention Commands you have to type in are printed in sans serif Code samples are printed in typewriter font Interesting items a
86. e either GPUTILS gplink or MPLAB s mplink exe If you use MPLAB and an interrupt function then the linker script file vectors section will need to be enlarged to link with mplink Pic device specific header and c source files are automatically generated from MPLAB include files which are published by Microchip with a special requirement that they are only to be used with authentic Microchip devices This reqirement prevents to publish generated header and c source files under the GPL compatible license so they are located in non free directory see section 2 3 In order to include them in include and library search paths the use non free command line option should be defined NOTE the compiled code which use non free pic device specific libraries is not GPL compatible Here is aMakefile using GPUTILS C O sdcc y non fr mpicl4 pl6f877 c lt PRJ hex OBJS gplink m s PRJ 1lkr o S PRJ hex OBJS libsdcc lib Here is aMakefile using MPLAB C O sdcc S V non fr mpicl4 p16f877 lt mpasmwin q o x asm PRJ hex OBJS mplink v PRJ lkr m PRJ map o PRJ hex OBJS libsdcc lib 63 4 5 THE PIC14 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS Please note that indentations within a Makefile have to be done with a tabulator character 4 5 5 Command Line Options Besides the switches common to all SDCC backends the PIC 14 port accepts the following options for an updated
87. e g unsigned char foo char i __reentrant Since stack space on 8051 is limited the reentrant keyword or the stack auto option should be used sparingly Note that the reentrant keyword just means that the parameters amp local variables will be allocated to the stack it does not mean that the function is register bank independent Local variables can be assigned storage classes and absolute addresses e g unsigned char foo __xdata int parm __xdata unsigned char i _ bit bvar _ data __at 0x31 unsigned char j In the above example the parameter parm and the variable i will be allocated in the external ram bvar in bit ad dressable space and j in internal ram When compiled with stack auto or when a function is declared as reentrant this should only be done for static variables It is however allowed to use bit parameters in reentrant functions and also non static local bit variables are supported Efficient use is limited to 8 semi bitregisters in bit space They are pushed and popped to stack as a single byte just like the normal registers 3 8 Overlaying For non reentrant functions SDCC will try to reduce internal ram space usage by overlaying parameters and local variables of a function if possible Parameters and local variables of a function will be allocated to an overlayable segment if the function has no other function calls and the function is non reentrant and the memory model is small If an explic
88. e libc library there exist the functions that are used to write to each of the above streams These are __stream_usart_putchar writes a character at the USART stream __stream_mssp_putchar writes a character at the MSSP stream putchar dummy function This writes a character to a user specified manner In order to increase performance putchar is declared in stdio h as having its parameter in WREG 1t has the wparam keyword In stdio h exists the macro PUTCHAR arg that defines the putchar function in a user friendly way arg 1s the name of the variable that holds the character to print An example follows include lt picl8fregs h gt tinclude lt stdio h gt PUTCHAR PORTA e Cc x dump character c to PORTA x 73 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS void main void stdout STREAM USER x this is not necessary since stdout points x by default to STREAM_USER x printf This is a printf testin 4 6 17 2 Printing functions PIC16 contains an implementation of the printf family of functions There exist the following functions extern unsigned int sprintf char buf char xfmt extern unsigned int vsprintf char buf char fmt va_list ap extern unsigned int printf char xfmt extern unsigned int vprintf char fmt va_lista ap extern unsigned int fprintf FILE x fp char x fmt extern unsigned int
89. e name Note this is an alternate method of loading file for debugging frame print information about current frame set srcmode Toggle between C source amp assembly source simulator command Send the string following to the simulator the simulator response is displayed Note the debugger does not interpret the command being sent to the simulator so if a command like go is sent the debugger can loose its execution context and may display incorrect values quit Watch me now Iam going Down My name is Bobby Brown 79 5 1 DEBUGGING WITH SDCDB CHAPTER 5 DEBUGGING 5 1 6 Interfacing SDCDB with DDD The portable network graphics File http sdcc svn sourceforge net viewvc checkoutx sdcc trunk sdec doc figures ddd_example png shows a screenshot of a debugging session with DDD Unix only on a simulated 8032 The debugging session might not run as smoothly as the screenshot suggests The debugger allows setting of breakpoints displaying and changing variables single stepping through C and assembler code The source was compiled with sdcc debug ddd_example c and DDD was invoked with ddd debugger sdcdb cpu 8032 ddd_example 5 1 7 Interfacing SDCDB with XEmacs Two files in emacs lisp are provided for the interfacing with XEmacs sdcdb el and sdcdbsrc el These two files can be found in the prefix bin directory after the installation is complete These files need to be loaded into XEmacs for
90. e of the register allocator loop induction optimization causes an increase in register pressure which may cause unwanted spilling of other temporary variables into the stack data space The compiler will generate a warning message when it is forced to allocate extra space either on the stack or data space If this extra space allocation is undesirable then induction optimization can be eliminated either for the entire source file with noinduction option or for a given function only using pragma noinduction Loop Invariant tor a 0 3 Tr E kK ch Ls changed to itemp k 1 for i 0 i lt 100 1 f itemp As mentioned previously some loop invariants are not as apparent all static address computations are also moved out of the loop Strength Reduction this optimization substitutes an expression by a cheaper expression for i 0 i lt 100 i ar ix5 1x3 changed to itempl 0 itemp2 ll o 92 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA for i 0 i lt 100 i ar itempl itemp2 itempl 5 itemp2 3 The more expensive multiplication is changed to a less expensive addition 8 1 5 Loop Reversing This optimization is done to reduce the overhead of checking loop boundaries for every iteration Some simple loops can be reversed and implemented using a decrement and jump if not zero instruction SDCC checks for the following criterion to determine if a loop is r
91. e option codeseg constseg lt name gt Use this name max 8 characters for the const segment See option constseg The preprocessor SDCPP supports the following pragma directives pedantic_parse_number Pedantic parse numbers so that situations like Oxfe LO_B 3 are parsed properly and the macro LO_B 3 gets expanded Default is off See also the pedantic parse number com mand line option on page 26 Below is an example on how to use this pragma Note this functionality is not in conformance with standard pragma pedantic_parse_number define LO_B x x amp Oxff unsigned char foo void unsigned char c 0xfe LO_B 3 return c preproc_asm switch the __asm __endasm block preprocessing on off Default is on Below is an example on how to use this pragma pragma preproc_asm this is a c code nop define NOP void foo void while 1 NOP __asm this is an assembler nop instruction it is not preprocessed to since the asm preprocessing is disabled NOP __endasm 57 3 19 PRAGMAS CHAPTER 3 USING SDCC The pragma preproc_asm should not be used to define multilines of assembly code even if it supports it since this behavior is only a side effect of sdcpp __asm __endasm implementation in combi nation with pragma preproc_asm and is not in conformance with the C standard This behavior might be changed in the future sdcpp versions To define mult
92. e pedantic 32 no c code in asm 31 no gen comments 31 no pack iram 27 28 no peep 30 no peep comments 31 no std crt0 46 no xinit opt 29 46 nogcse 29 noinduction 29 noinvariant 29 nojtbound 29 nolabelopt 29 noloopreverse 29 nooverlay 30 nostdinc 31 nostdlib 31 opt code size 30 opt code speed 30 out fmt ihx 27 out fmt s19 22 27 pack iram 27 28 peep asm 30 48 peep file 30 98 print search dirs 19 31 short is 8bits 32 stack auto 28 30 39 41 52 55 56 99 stack loc lt Value gt 27 36 stack size lt Value gt 28 std c89 7 8 32 100 std c99 7 8 100 std sdcc89 32 std sdcc99 32 use non free 32 63 67 69 use stdout 31 33 ve 31 33 verbose 31 version 30 xdata loc lt Value gt 36 xram loc lt Value gt 27 xram size lt Value gt 28 36 xstack 28 34 55 xstack loc lt Value gt 27 Aquestion answer 26 C 26 D lt macro value gt 26 E 26 30 I lt path gt 26 L lt path gt 27 M 26 MM 26 S 31 Umacro 26 V 31 Wa asmOption asmOption 31 WI linkOption linkOption 27 111 INDEX INDEX Wp preprocessorOption preprocessorOption 26 c 30 dD 26 dM 26 dN 26 mds390 25 mds400 25 mgbz80 26 mhc08 26 mmcs51 25 mpic14 26 mpic16 26 mxa51 26 mz80 26 o lt path file gt 30 pedantic parse number
93. e string h file If it cannot find the string h file then the problem is that SDCC cannot find the usr local share sdcc include directory see the section 2 8 Install trouble shooting section for suggestions Use option print search dirs to find exactly where SDCC is looking for the include and lib files 2 8 Install Trouble shooting 2 8 1 If SDCC does not build correctly A thing to try is starting from scratch by unpacking the tgz source package again in an empty directory Configure 1t like configure 2 gt amp 1 tee configure log and build it like make 2 gt amp 1 tee make log If anything goes wrong you can review the log files to locate the problem Or a relevant part of this can be attached to an email that could be helpful when requesting help from the mailing list 2 8 2 What the configure does The configure command is a script that analyzes your system and performs some configuration to ensure the source package compiles on your system It will take a few minutes to run and will compile a few tests to determine what compiler features are installed 2 8 3 What the make does This runs the GNU make tool which automatically compiles all the source packages into the final installed binary executables 2 9 COMPONENTS OF SDCC CHAPTER 2 INSTALLING SDCC 2 8 4 What the make install command does This will install the compiler other executables libraries and include files into the appropriat
94. e the generated ISR code more efficient since it will not have to save registers on the stack The using attribute will have no effect on the generated code for a non interrupt function but may occasionally be useful anyway pending Note nowadays the using attribute has an effect on the generated code for a non interrupt function An interrupt function using a non zero bank will assume that it can trash that register bank and will not save 1t Since high priority interrupts can interrupt low priority ones on the 8051 and friends this means that if a high priority ISR using a particular bank occurs while processing a low priority ISR using the same bank terrible and bad things can happen To prevent this no single register bank should be used by both a high priority and a low priority ISR This is probably most easily done by having all high priority ISRs use one bank and all low priority ISRs use another If you have an ISR which can change priority at runtime you re on your own I suggest using the default bank zero and taking the small performance hit It is most efficient if your ISR calls no other functions If your ISR must call other functions it is most efficient if those functions use the same bank as the ISR see note 1 below the next best is if the called functions use bank zero It is very inefficient to call a function using a different non zero bank from an ISR possible exception if a function is called ONLY from in
95. ecognizes the following expressions to yield the higher order byte or word and generates optimized code for it e g unsigned int gint unsigned long int glong foo unsigned char hob1 hob2 unsigned int howl how2 hobl gint gt gt 8 amp OxFF hob2 glong gt gt 24 howl glong gt gt 16 OxFFFF how2 glong gt gt 8 will generate the following code Or lt 2 hob c 15 0037 85x01x06 92 mov foo_hob1_1_1 _gint 1 93 hobo Le 003A 85 05 07 94 mov foo_hob2_1_1 _glong 3 ISi hob c 17 003D 85x04x08 96 mov foo_how1_1_1 _glong 2 0040 85x05x x09 97 mov _foo_how1_1_1 1 _ glong 3 0043 85 03x0A 98 mov foo_how2_1_1 _glong 1 0046 85x04x0B 99 mov _foo_how2_1_1 1 _glong a 23 Again variations of these cases may not be recognized They are standard C expressions so I heartily recommend these be the only way to get the higher order byte word it is portable Of course it will be recognized even if it is embedded in other expressions e g xyz gint gint gt gt 8 amp OxFF will still be recognized 97 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA 8 1 13 Peephole Optimizer The compiler uses a rule based pattern matching and re writing mechanism for peep hole optimization It is inspired by copt a peep hole optimizer by Christopher W Fraser cwfraser microsoft com A default set of rules are co
96. elects small stack model 8 bit stack and frame pointers Supports 256 bytes stack size large Selects large stack model 16 bit stack and frame pointers Supports 65536 bytes stack size pno banksel Do not generate BANKSEL assembler directives extended Enable extended instruction set literal offset addressing mode Use with care 4 6 2 2 Optimization Options obanksel n Set optimization level for inserting BANKSELs 0 no optimization hb checks previous used register and if it is the same then does not emit BANKSEL accounts only for labels 65 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 2 tries to check the location of even different symbols and removes BANKSELs if they are in the same bank Important There might be problems if the linker script has data sections across bank borders denable peeps Force the usage of peepholes Use with care no optimize goto Do not use conditional BRA instead of GOTO optimize cmp Try to optimize some compares optimize df Analyze the dataflow of the generated code and improve it 4 6 2 3 Assembling Options asm Sets the full path and name of an external assembler to call mplab comp MPLAB compatibility option Currently only suppresses special gpasm directives 4 6 2 4 Linking Options link Sets the full path and name of an external linker to call preplace udata with kword Replaces the default udata keyword for allocating unitialized
97. encies are all the files include d in it This rule may be a single line or may be continued with newline if it is long The list of rules is printed on standard output instead of the preprocessed C program M implies E C Tell the preprocessor not to discard comments Used with the E option MM Like M but the output mentions only the user header files included with include file System header files included with include lt file gt are omitted Aquestion answer Assert the answer answer for question in case it is tested with a preprocessor conditional such as if question answer A disables the standard assertions that normally describe the target machine Umacro Undefine macro macro U options are evaluated after all D options but before any include and imacros options dM Tell the preprocessor to output only a list of the macro definitions that are in effect at the end of preprocessing Used with the E option dD Tell the preprocessor to pass all macro definitions into the output in their proper sequence in the rest of the output dN Like dD except that the macro arguments and contents are omitted Only define name is included in the output pedantic parse number Pedantic parse numbers so that situations like Oxfe LO_B 3 are parsed properly and the macro LO_B 3 gets expanded See also pragma pedantic_parse_
98. eprecated and will be removed in future versions acall ajmp Replaces the three byte instructions Icall ljmp with the two byte instructions acall ajmp Only use this option if your code is in the same 2k block of memory You may need to use this option for some 8051 derivatives which lack the Icall ljmp instructions 3 2 5 DS390 DS400 Options model flat24 Generate 24 bit flat mode code This is the one and only that the ds390 code generator supports right now and is default when using mds390 See section Memory Models for more details protect sp update disable interrupts during ESP SP updates stack 10bit Generate code for the 10 bit stack mode of the Dallas DS80C390 part This is the one and only that the ds390 code generator supports right now and is default when using mds390 In this mode the stack is located in the lower 1K of the internal RAM which is mapped to 0x400000 Note that the support is incomplete since it still uses a single byte as the stack pointer This means that only the lower 256 bytes of the potential 1K stack space will actually be used However this does allow you to reclaim the precious 256 bytes of low RAM for use for the DATA and IDATA segments The compiler will not generate any code to put the processor into 10 bit stack mode It is important to ensure that the processor is in this mode before calling any re entrant functions compiled with this option In principle this should work with the stack auto
99. et assume it is saved in buffer c is compiled with SDCC then a corresponding buffer asm file is generated We define a new function to_buffer_asm in file buffer c in which we cut and paste the generated code removing unwanted comments and some Then add __asm and endasm to the beginning and the end of the function body x With a cut and paste from the asm file we have something to start with The function is not yet OK registers aren t saved void to_buffer_asm unsigned char c 5 _plosgff are the assembler options used in http sdcc svn sourceforge net viewvc sdcc trunk sdcc device lib mcs51 Makefile in view markup Note that the single underscore form _asm and _endasm are not C99 compatible and for C99 compatibility the double underscore form __asm and __endasm has to be used The latter is also used in the library functions 46 3 13 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC __asm mov r2 dpl buffer c if head unsigned char tail 1 cast needed to avoid promotion to integer mov a _tail dec a mov r3 a mov a _head cjne a ar3 00106 ret 001065 buffer c buf head c x access to a 256 byte aligned array x mov r3 _head inc _head mov dpl r3 mov dph _buf gt gt 8 mov a r2 movx dptr a 001035 ret endasm The new file buffer c should compile with only one warning about the unreferenced function argument c Now we hand optimize the as
100. eversible note more sophisticated compilers use data dependency analysis to make this determination SDCC uses a more simple minded analysis e The for loop is of the form for lt symbol gt lt expression gt lt sym gt 1 lt for body gt lt sym gt lt lt lt expression gt lt sym gt e The lt for body gt does not contain continue or break e All goto s are contained within the loop e No function calls within the loop e The loop control variable lt sym gt is not assigned any value within the loop e The loop control variable does NOT participate in any arithmetic operation within the loop e There are NO switch statements in the loop 8 1 6 Algebraic Simplifications SDCC does numerous algebraic simplifications the following is a small sub set of these optimizations 1 rh 0 changed to i j i 2 for unsigned i changed to i gt gt 1 a She changed to i 0 isej 1 changed to i j Note the subexpressions given above are generally introduced by macro expansions or as a result of copy constant propagation 8 1 7 SDCC can optimize switch statements to jump tables It makes the decision based on an estimate of the generated code size SDCC is quite liberal in the requirements for jump table generation switch Statements e The labels need not be in order and the starting number need not be one or zero the case labels are in numerical seq
101. ex format 22 27 77 Intermediate dump options 32 interrupt 36 40 43 46 48 52 56 interrupt 36 40 48 interrupt jitter 43 interrupt latency 42 interrupt mask 42 interrupt priority 43 interrupt vector table 27 40 41 56 interrupts 43 jump tables 93 K amp R style 100 Labels 49 Libraries 23 27 31 36 53 54 Linker 23 Linker documentation 84 113 INDEX INDEX Linker options 27 lint syntax checking tool 32 76 little endian 96 Live range analysis 32 102 103 106 local variables 39 55 83 lock 43 long 32 bit 52 long long not supported 100 Loop optimization 32 92 106 Loop reversing 29 93 mailing list 85 Mailing list s 88 89 main return 31 Makefile 86 malloc h 54 MCSS1 25 __mes51 59 MCS51 memory 36 MCS51 memory model 55 MCSS1 options 27 MCSS1 variants 60 98 Memory bank pic 14 62 Memory map 22 83 Memory model 35 39 55 Microchip 62 65 Modulus 41 Motorola S19 format 22 27 MSVC output style 31 Multiplication 39 41 93 106 naked 50 __naked 48 56 _naked 48 56 Naked functions 48 near storage class 33 __near storage class 33 Nibble swapping 96 objdump tool 22 86 Object file 22 Optimization options 29 Optimizations 91 103 Options assembler 31 Options DS390 28 Options GBZ80 29 Options intermediate dump 32 Options linker 27 Options MCS51 27 Options optimization 29 Opt
102. gister bank or with register bank 0 using 0 the compiler will save the registers used by itself on the stack upon entry and restore them at exit however if such an interrupt service routine calls another function then the entire register bank will be saved on the stack This scheme may be advantageous for small interrupt service routines which have low register usage If the interrupt service routine is defined to be using a specific register bank then only a b dptr amp psw are saved and restored if such an interrupt service routine calls another function using another register bank then the entire register bank of the called function will be saved on the stack This scheme is recommended for larger interrupt service routines 3 9 3 HC08 Interrupt Service Routines Since the number of interrupts available is chip specific and the interrupt vector table always ends at the last byte of memory the interrupt numbers corresponds to the interrupt vectors in reverse order of address For example interrupt 1 will use the interrupt vector at Oxfffc interrupt 2 will use the interrupt vector at Oxfffa and so on However interrupt O the reset vector at Oxfffe is not redefinable in this way instead see section 3 12 for details on customizing startup 41 3 10 ENABLING AND DISABLING INTERRUPTS CHAPTER 3 USING SDCC 3 9 4 Z80 Interrupt Service Routines The Z80 uses several different methods for determining the correct interrupt vector depen
103. gure gnu nable floats instead of just configure gnu Also make sure that at least 1ibc stdio vfprintf c is actually re compiled e g by touching it after the configure run or deleting its o file The more common appraoch of compiling vfprintf c manually with DUSE_FLOATS 1 should also work but is untested 69 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 10 Adding New Devices to the Port Adding support for a new 16 bit PIC MCU requires the following steps 1 Create picDEVICE c and picDEVICE h from pDEVICE inc using perl path to sdcc support scripts inc2h picl6 pl path to gputils header pDEVICE inc 2 mv picDEVICE h path to sdcc device include picl6 3 mv picDEVICE c path to sdcc device lib picl6 libdev 4 Add DEVICE to path to sdcc device lib picl6 pics all Note No 18f prefix here 5 Either a add the new device to path to sdcc device lib pic16 1libio x ignore to suppress building any of the I O libraries for the new device or b add the device family to path to sdcc support scripts picl8fam h gen pl to assign I O styles run the pic18fam h gen pl script to generate picl8fam h gen replace your existing picl8fam h with the generated file and if required implement new VO styles in path to sdcc device include picl6 adc i2c usart h and path to sdcc device lib picl16 libio x x 6 Edit path to sdcc device include picl6 pi
104. h E oe babe ha 281 ESDCC does wot busdieormecth 4 066 4 Ks Ska SEH ROS ER 28 2 Whatthe feonieure does eeso oeiee su a ee ee eee Bhs mee Whatthe make GES ona ae SR SRM RS aoa AS Oe 2 8 4 What the make install command does a oa o o e e 29 Components ol SDG ec eke RA RE A a e pe 29 1 0ee The Compiler 203 sea kee ER Rae e A Ee ee eS 29 2 steppe Ihe C Preprocessor cis das BAe e BAe Oe ee Ace 2 9 3 sdas sdld The Assemblers and Linkage Editors 2 2000 29 4 51 5280 shoOs The Simulators 2 44 4 2 4 6868080 dei www bab e 29 35 lt sdedb source Level Debuseer oe cccog 664 Ae A Oe eee Oe 3 Using SDCC SA COMPE ooo cee e a eva de ERNE He hs eb Pee ee PP ee ae be hes 3 1 1 Single Source File Projects so stoce s eA OES ee SE SR wo 3 12 Postprocessing the Intel Hex file os ce ee ee ee ee ee EES 3 1 3 Projects with Multiple Source Files sos a ccie eaa sere EN RE ESE OS 3 1 4 Projects with Additional Libraries ee 3 1 5 Using sdcclib to Create and Manage Libraries o o 3 1 6 Using arto Create and Manage Libraries co lt me ne NN 0 D CONTENTS CONTENTS Ee 33 3 4 aed 3 6 a 3 8 310 a ce Command Lane OPONE lt sou eG ea AAS EER eS RS 25 3 2 1 Processor Selection Opuions coses Red bee ee ee es 25 Aza Preprocessor OPONE o s s sopre a ea RS ee oS ee ea a a 26 3 2 5 Linker OP
105. he int long reent compiler option Note the type promotion required by ANSI C can cause 16 bit routines to be used without the programmer being aware of it See f e the cast unsigned char tail 1 within the if clause in section 3 13 1 Calling other functions from an interrupt service routine is not recommended avoid it if possible Note that when some function is called from an interrupt service routine it should be preceded by a pragma nooverlay if it is not reentrant Furthermore nonreentrant functions should not be called from the main program while the interrupt service routine might be active They also must not be called from low priority interrupt service routines while a high priority interrupt service routine might be active You could use semaphores or make the function critical if all parameters are passed in registers Also see section 3 8 about Overlaying and section 3 11 about Functions using private register banks 3 9 2 MCS51 DS390 Interrupt Service Routines Interrupt numbers and the corresponding address amp descriptions for the Standard 8051 8052 are listed below SDCC will automatically adjust the to the maximum interrupt number specified Interrupt Description Vector Address 0 External 0 0x0003 1 Timer 0 0x000b 2 External 1 0x0013 3 Timer 1 0x001b 4 Serial 0x0023 5 Timer 2 8052 0x002b n 0x0003 8 n If the interrupt service routine is defined without using a re
106. he pic16 targets see 4 6 9 If you re short on code memory you might want to use printf_small instead of printf For the mcs51 there additionally are assembly versions printf_tiny subset of printf using less than 270 bytes and printf_fast and printf_fast_f floating point aware version of printf_fast which should fit the requirements of many embedded systems printf_fast can be customized by unsetting defines to not support long variables and field widths Be sure to use only one of these printf options within a project Feature matrix of different printf options on mcs51 mes51 printf printf printf small printf fast printf fast_f printf_tiny USE_FLOATS 1 filename printf_large c printf_large c printfl c printf_fast c printf_fast_f c printf_tiny c Hello World size 1 7k 2 4k 4 3k 5 6k 1 2k 1 8k 1 3k 1 3k 1 9k 1 9k 0 44k 0 44k small large as 1 4k 2 0k 2 8k 3 7k 0 45k 1 2k 1 2k 1 6k 1 6k 0 26k 0 26k small large 0 47k _ltoa formats cdiopsux cdfiopsux cdosx cdsux cdfsux cdsux long 32 bit a oi x x x x x byte arguments b b g 7 g p on stack float format f Gof float formats e g i j i field width x x x xX 10Range limited to 4294967040 precision limited to 8 digits past decimal 53 3 17 LIBRARY ROUTINES CHAPTER 3 USING SDCC mes51 printf printf printf_small printf fast printf fast_f pri
107. her SDCC lang age extensions cocoa sera A a E 37 331 Binary Constants c o ec ersam ee e a A 37 Absol te Addnessi09 150 seo 4 ee ORAS OR ER BO RAE EMER ea OS 38 Parameters amp Local Variables os o cored cerea Re e ss a ee we 39 OPE VIDE lt a Gado A Rae hod he AAA a Bo He Bae BS 39 Interrupt Service Routines 2 4 5 ep he ee ee ew ee 40 33 1 General IOMA osos eee be ER eA Cen E Seb 4s RA eS 40 3 9 1 1 Common interrupt pitfall variable not declared volatile 40 3 9 1 2 Common interrupt pitfall non atomic access o o oo oo 40 3 9 1 3 Common interrupt pitfall stack overflow o o o o ooo o 41 3 9 1 4 Common interrupt pitfall use of non reentrant functions 41 3 9 2 MCS51 DS390 Interrupt Service Routines e 41 3 9 3 HCO8 Interrupt Service Routines s e s sere ceres eres ee es 41 3 94 Z8O Interrupt Service Routines ooo cosas ra a a AR 42 Enabling and Disabling Interrupts 2 2 2 2 0 0 000 0000000 42 3 10 1 Critical Functions and Critical Statements e 42 3 10 2 Enabling and Disabling Interrupts directly o o e 42 310 3 Semaphore locking mesSlas390 ced we we ee PARE EES GS BH SES a 43 Functions using private register banks mcs51 ds390 2 2 ee ee eee 43 Aileen di RES 44 3 12 1 MUSSEDS90 SETUP Code sie e A a ee RR 44 2 EOS Startap COE soto se ae oe eh oe AA OE eb ee See 46 ALZA Z
108. hx gt sourcefile hex 22 3 1 COMPILING CHAPTER 3 USING SDCC The separately available srecord package additionally allows to set undefined locations to a predefined value to insert checksums of various flavours crc add xor and to perform other manipulations convert split crop offset es srec_cat sourcefile ihx intel o sourcefile hex intel An example for a more complex command line could look like srec_cat sourcefile ihx intel fill 0x12 0x0000 Oxfffe little endian checksum negative Oxfffe 0x02 0x02 o source file hex intel The srecord package is available at http sf net projects srecord 3 1 3 Projects with Multiple Source Files SDCC can compile only ONE file at a time Let us for example assume that you have a project containing the following files fool c contains some functions foo2 c contains some more functions foomain c contains more functions and the function main The first two files will need to be compiled separately with the commands sdcc c foo1 c sdcc c foo2 c Then compile the source file containing the main function and link the files together with the following command sdcc foomain c foo1 rel foo2 rel Alternatively foomain c can be separately compiled as well sdcc c foomain c sdcc foomain rel foo1 rel foo2 rel The file containing the main function MUST be the FIRST file specified in the command line since the linkage editor processes file in the order they are prese
109. i gt gt 7 i lt lt 1 5 left bit rotation 95 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA 8 1 10 Nibble and Byte Swapping Other special cases of the bit shift operations are nibble or byte swapping SDCC recognizes the following expres sions unsigned char i unsigned int j i i lt lt 4 i gt gt 4 jJ j lt lt 8 3 gt gt 8 99599 and generates a swap instruction for the nibble swapping or move instructions for the byte swapping The j example can be used to convert from little to big endian or vice versa If you want to change the endianness of a signed integer you have to cast to unsigned int first Note that SDCC stores numbers in little endian format i e lowest order first 8 1 11 Highest Order Bit Any Order Bit It is frequently required to obtain the highest order bit of an integral type long int short or char types Also obtaining any other order bit is not uncommon SDCC recognizes the following expressions to yield the highest order bit and generates optimized code for it e g unsigned int gint foo unsigned char hobl aobl bit hob2 hob3 aob2 aob3 hobl gint gt gt 15 amp 1 hob2 gint gt gt 15 amp 1 hob3 gint amp 0x8000 aobl gint gt gt 9 1 aob2 gint gt gt 8 1 aob3 gint amp 0x0800 will generate the following code 61 gt hob c 7 000A E5x01 62 m
110. if the cyclomatic complexity reported by SDCC exceeds 10 you should think about simplification of the function logic Note that the complexity level is not related to the number of lines of code in a function Large functions can have low complexity and small functions can have large complexity levels SDCC uses the following formula to compute the complexity complexity number of edges in control flow graph number of nodes in control flow graph 2 Having said that the industry standard is 10 you should be aware that in some cases it be may unavoidable to have a complexity level of less than 10 For example if you have switch statement with more than 10 case labels each case label adds one to the complexity level The complexity level is by no means an absolute measure of the algorithmic complexity of the function it does however provide a good starting point for which functions you might look at for further optimization 8 4 Retargetting for other Processors The issues for retargetting the compiler are far too numerous to be covered by this document What follows is a brief description of each of the seven phases of the compiler and its MCU dependency e Parsing the source and building the annotated parse tree This phase is largely MCU independent except for the language extensions Syntax amp semantic checks are also done in this phase along with some initial optimizations like back patching labels and the pattern matching optim
111. if you want to change a file you can leave the original file untouched in the source directory Simply copy it to the build directory edit it enter make clean rm Makefile dep and make make will do the rest for you 2 5 Building the Documentation Add enable doc to the configure arguments to build the documentation together with all the other stuff You will need several tools LyX ATEX KIEX2HTML pdflatex dvipdf dvips and makeindex to get the job done Another possibility is to change to the doc directory and to type make there You re invited to make changes and additions to this manual sdcc doc sdccman lyx Using LyX http www lyx org as editor is straightforward Prebuilt documentation in html and pdf format is available from http sdcc sf net snap php 2 6 Reading the Documentation Currently reading the document in pdf format is recommended as for unknown reason the hyperlinks are working there whereas in the html version they are not You ll find the pdf version at http sdcc sf net doc sdccman pdf A html version should be online at http sdcc sf net doc sdccman html index html This documentation is in some aspects different from a commercial documentation e It tries to document SDCC for several processor architectures in one document commercially these probably would be separate documents products This document currently matches SDCC for mcs51 and DS390 best and does give too few informatio
112. iled into the binaries Moreover the install path can be changed by defining DESTDIR make install DESTDIR HOME sdcc rpm Please note that DESTDIR must have a trailing slash 2 3 Search Paths Some search paths or parts of them are determined by configure variables in italics see section above Further search paths are determined by environment variables during runtime The paths searched when running the compiler are as follows the first catch wins 1 Binary files preprocessor assembler and linker Search path default Win32 builds SDCC_HOME PPREFIX2BIN_DIR SDCC_HOME bin SDCC_HOME bin Path of argv 0 if available Path of argv 0 Path of argv 0 PATH PATH PATH 2 Include files Search path default Win32 builds 1 I dir I dir I dir 2 SDCC_INCLUDE SDCC_INCLUDE SDCC_INCLUDE 3 SDCC_HOME SDCC_HOME SDCC_HOME include PREFIX2DATA_DIR share sdcc include INCLUDE_DIR_SUFFIX 4 path argv 0 path argv 0 path argv 0 include BIN2DATADIR sdcc include INCLUDE_DIR_SUFFIX 5 DATADIR usr local share not on Win32 INCLUDE_DIR_SUFFIX sdec include 6 SDCC_HOME SDCC_HOME share SDCC_HOME non free include PREFIX2DATA_DIR sdcc non free include non free INCLUDE_DIR_SUFFIX 7 path argv 0 path argv 0 path argv 0 non free include BIN2DATADIR sdcc non free include non free INCLUDE_DIR_SUFFIX 8 DATADIR
113. ilines of assembly code you have to include each assembly line into it s own __asm __endasm block Below is an example for multiline assembly defines define Nop __asm nop __endasm define ThreeNops Nop Nop Nop void foo void ThreeNops e sdcc_hash Allow naked hash in macro definition for example define DIR_LO x x amp Oxff Default is off Below is an example on how to use this pragma pragma preproc_asm pragma sdcc_hash define ROMCALL x mov R6_B3 x amp Oxff mov R7_B3 x gt gt 8 amp Oxff Teall __romcall __asm ROMCALL 72 ___endasm Some of the pragmas are intended to be used to turn on or off certain optimizations which might cause the compiler to generate extra stack and or data space to store compiler generated temporary variables This usually happens in large functions Pragma directives should be used as shown in the following example they are used to control options and optimizations for a given function pragma save save the current settings x pragma nogcse turnoff global subexpression elimination x pragma noinduction turn off induction optimizations x int foo large code x pragma restore turn the optimizations back on x The compiler will generate a warning message when extra space is allocated It is strongly recommended that the save and restore pragmas be used when changing options for
114. information The first with extension map shows all the variables and segments The second with extension mem shows the final memory layout The linker will complain either if memory segments overlap there is not enough memory or there is not enough space for stack If you get any linking warnings and or errors related to stack or segments allocation take a look at either the map or mem files to find out what the problem is The mem file may even suggest a solution to the problem 3 4 2 Z80 Z180 Storage Class Language Extensions 3 4 2 1 sfr in out to 8 bit addresses The Z80 family has separate address spaces for memory and input output memory I O memory is accessed with special instructions e g __sfr __at 0x78 IoPort x define a var in I O space at 78h called ToPort Writing 0x01 to this variable generates the assembly code 3E 01 ld a 0x01 D3 78 out _IoPort a 3 4 2 2 banked sfr in out to 16 bit addresses The keyword banked is used to support 16 bit addresses in I O memory e g sfr _ banked __at 0x123 IoPort Writing 0x01 to this variable generates the assembly code 01 23 01 ld bc _IoPort 3E 01 ld a 0x01 ED 79 out c a 3 4 2 3 sfr in0 out0 to 8 bit addresses on Z180 HD64180 The compiler option portmode 180 80 and a compiler pragma portmode z180 z80 is used to turn on off the Z180 HD64180 port addressing instructions in0 out0 instead of in out
115. inker model large Generate code for Large model programs see section Memory Models for more details If this option is used all source files in the project have to be compiled with this option It must also be used when invoking the linker model huge Generate code for Huge model programs see section Memory Models for more details If this option is used all source files in the project have to be compiled with this option It must also be used when invoking the linker xstack Uses a pseudo stack in the pdata area usually the first 256 bytes in the external ram for allocating variables and passing parameters See section 3 18 1 2 External Stack for more details iram size lt Value gt Causes the linker to check if the internal ram usage is within limits of the given value xram size lt Value gt Causes the linker to check if the external ram usage is within limits of the given value code size lt Value gt Causes the linker to check if the code memory usage is within limits of the given value stack size lt Value gt Causes the linker to check if there is at minimum lt Value gt bytes for stack pack iram Causes the linker to use unused register banks for data variables and pack data idata and stack together This is the default and this option will probably be removed along with the removal of no pack iram no pack iram deprecated Causes the linker to use old style for allocating memory areas This option is now d
116. ions other 30 Options PIC16 65 Options preprocessor 26 Options processor selection 25 Options SDCC configuration 10 Options Z80 29 Oscilloscope 76 Other SDCC language extensions 37 Overlaying 39 P2 mcs51 sfr 34 55 60 packihx tool 22 84 Parameter passing 50 Parameters 39 Parsing 103 Patch submission 88 90 pdata mcs51 ds390 storage class 27 28 34 55 60 __pdata mcs51 ds390 storage class 34 PDF version of this document 18 pedantic 26 31 32 56 57 Peephole optimizer 30 48 98 PIC 65 PIC14 26 62 64 Environment variables SDCC_PIC14_SPLIT_LOCALS 64 interrupt 63 Options debug extra 64 no pcode opt 64 stack loc 64 stack size 64 PIC16 26 65 67 69 71 72 84 Defines __picl6 67 pic 8fxxxx 67 __pic18f xxxx 67 STACK_MODEL_nnn 67 Environment variables NO_REG_OPT 66 OPTIMIZE_BITFIELD_POINTER_GET 66 Header files 69 interrupt 72 Libraries 69 MPLAB 66 Options callee saves 65 fommit frame pointer 65 Pragmas pragma code 68 pragma stack 67 shadowregs 71 stack 71 75 wparam 71 Pointer 35 36 pragma callee_saves 30 56 pragma codeseg 57 pragma constseg 57 pragma disable_warning 56 pragma exclude 49 56 pragma less_pedantic 56 pragma nogcse 29 56 58 pragma noinduction 29 56 58 92 pragma noinvariant 29 56 pragma noiv 56 114 INDEX INDEX pragma nojtbound 29 56 95 pragma noloopreverse 56 pragma noove
117. ior struct int ai 2 char 2 int b 2 Pos Ll 2 x S a 1 s b 2 x libraries included in sdcc packages are in ar format in sdcc version 2 9 0 and higher See section 3 1 6 special sdcc keywords which are not preceded by a double underscore are deprecated in version 3 0 and higher See section 8 2 ANSI Compliance targets for xa51 and avr are disabled by default in version 3 0 and higher in sdcc version 3 0 and higher sdldgb and sdldz80 don t support generation of GameBoy binary image format The makebin utility can be used to convert Intel Hex format to GameBoy binary image format in sdcc version 3 0 and higher sdldgb and sdldz80 don t support generation of rrgb GameBoy simulator map file and no gmb symbol file formats The as2gbmap utility can be used to convert sdld map format to rreb and no gmb file formats System Requirements What do you need before you start installation of SDCC A computer and a desire to compute The preferred method of installation is to compile SDCC from source using GNU gcc and make For Windows some pre compiled binary distributions are available for your convenience You should have some experience with command line tools and compiler use 1 6 OTHER RESOURCES CHAPTER 1 INTRODUCTION 1 6 Other Resources The SDCC home page athttp sdcc sourceforge net isa great place to find distribution sets You can also find links to the user mailing lists that offer help or dis
118. ious search in SDCC s sources for getenv 33 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 3 4 1 2 xdata far Variables declared with this storage class will be placed in the external RAM This is the default storage class for the Large Memory model e g __xdata unsigned char test_xdata Writing 0x01 to this variable generates the assembly code 90s00r00 mov dptr _test_xdata 74 01 mov a 0x01 FO movx dptr a 3 4 1 3 idata Variables declared with this storage class will be allocated into the indirectly addressable portion of the internal ram of a 8051 e g __idata unsigned char test_idata Writing 0x01 to this variable generates the assembly code 78r00 mov r0 _test_idata 76 01 mov r0 0x01 Please note the first 128 byte of idata physically access the same RAM as the data memory The original 8051 had 128 byte idata memory nowadays most devices have 256 byte idata memory The stack is located in idata memory 3 4 1 4 pdata Paged xdata access is just as straightforward as using the other addressing modes of a 8051 It is typically located at the start of xdata and has a maximum size of 256 bytes The following example writes 0x01 to the pdata variable Please note pdata access physically accesses xdata memory The high byte of the address is determined by port P2 or in case of some 8051 variants by a separate Special Function Register see section 4 1 This is the default storage class for
119. it storage class is specified for a local variable it will NOT be overlaid Note that the compiler not the linkage editor makes the decision for overlaying the data items Functions that are called from an interrupt service routine should be preceded by a pragma nooverlay if they are not reentrant Also note that the compiler does not do any processing of inline assembler code so the compiler might incor rectly assign local variables and parameters of a function into the overlay segment if the inline assembler code calls other c functions that might use the overlay In that case the pragma nooverlay should be used Parameters and local variables of functions that contain 16 or 32 bit multiplication or division will NOT be overlaid since these are implemented using external functions e g 39 3 9 INTERRUPT SERVICE ROUTINES CHAPTER 3 USING SDCC pragma save pragma nooverlay void set_error unsigned char errcd P3 errcd pragma restore void some_isr __interrupt 2 set_error 10 In the above example the parameter errcd for the function set_error would be assigned to the overlayable segment if the pragma nooverlay was not present this could cause unpredictable runtime behavior when called from an interrupt service routine The pragma nooverlay ensures that the parameters and local variables for the function are NOT overlaid 3 9 Interrupt Service Routines 3 9 1 General Information SDCC allows inter
120. izations like bit rotation etc e The second phase involves generating an intermediate code which can be easy manipulated during the later phases This phase is entirely MCU independent The intermediate code generation assumes the target machine has unlimited number of registers and designates them with the name iTemp The compiler can be made to dump a human readable form of the code generated by using the dumpraw option e This phase does the bulk of the standard optimizations and is also MCU independent This phase can be broken down into several sub phases Break down intermediate code iCode into basic blocks Do control flow amp data flow analysis on the basic blocks Do local common subexpression elimination then global subexpression elimination Dead code elimination Loop optimizations If loop optimizations caused any changes then do global subexpression elimination and dead code elimination again 101 8 4 RETARGETTING FOR OTHER PROCESSORS CHAPTER 8 SDCC TECHNICAL DATA e This phase determines the live ranges by live range I mean those Temp variables defined by the compiler that still survive after all the optimizations Live range analysis is essential for register allocation since these computation determines which of these Temps will be assigned to registers and for how long e Phase five is register allocation There are two parts to this process The first part I call register packing for
121. lding SDCC Using Microsoft Visual C 6 0 NET MSVC Download the source package either from the SDCC Subversion repository or from the snapshot builds http sdcec sourceforge net snap php it will be named something like sdcc src yyyymmdd rrrr tar bz2 SDCC is distributed with all the projects workspaces and files you need to build it using Visual C 6 0 NET except for SDCDB and ucSim The workspace name is sdcc dsw Please note that as it is now all the executables are created in a folder called sdecibin_vc Once built you need to copy the executables from sdcc bin_vc to sdcc bin before running SDCC WARNING Visual studio is very picky with line terminations it expects the OxOd Ox0a DOS style line endings not the Ox0a Unix style line endings When using the Subversion repository it s easiest to configure the svn client to convert automatically for you If however you are getting a message such as This makefile was not generated by Developer Studio etc etc when opening the sdcc dsw workspace or any of the dsp projects then you need to convert the Unix style line endings to DOS style line endings To do so you can use the unix2dos utility freely available on the internet Doug Hawkins reported in the sdcc user list that this works C Programming SDCC gt unix2dos sdcc dsw C Programming SDCC gt for R l in dsp do unix2dos YI In order to build SDCC with MSVC you need win32 executables of bison exe flex exe a
122. lds without an explicit signed modifier are implemented as unsigned 3 4 1 7 sfr sfr16 sfr32 sbit Like the bit keyword sfr sfr16 sfr32 sbit signify both a data type and storage class they are used to describe the special function registers and special bit variables of a 8051 eg sfr _ at 0x80 PO special function register PO at location 0x80 x 16 bit special function register combination for timer 0 with the high byte at location 0x8C and the low byte at location Ox8A x sfrl6 __at 0x8C8A TMRO _ sbit _ at 0xd7 CY x CY Carry Flag gt Special function registers which are located on an address dividable by 8 are bit addressable an sbit addresses a specific bit within these sfr 16 Bit and 32 bit special function register combinations which require a certain access order are better not declared using sfrl6 or sfr32 Allthough SDCC usually accesses them Least Significant Byte LSB first this is not guaranteed Please note if you use a header file which was written for another compiler then the sfr sfr16 sfr32 sbit Storage Class extensions will most likely be not compatible Specifically the syntax sfr PO 0x80 is compiled without warning by SDCC to an assignment of 0x80 to a variable called PO Nevertheless with the file compiler h it is possible to write header files which can be shared among different compilers see section 6 1 3 4 1 8 Pointers to MCS51 DS390 specific memory spaces S
123. libraries Libraries included in SDCC should have a license at least as liberal as the GNU Lesser General Public License LGPL If you have ported some library or want to share experience about some code which f e falls into any of these categories Busses PC CAN Ethernet Profibus Modbus USB SPI JTAG Media IDE Memory cards eeprom flash En Decryption Remote debugging Realtime kernel Keyboard LCD RTC FPGA PID then the sdcc user mailing list http sourceforge net mail group_id 599 would certainly like to hear about it Programmers coding for embedded systems are not especially famous for being enthusiastic so don t expect a big hurray but as the mailing list is searchable these references are very valuable Let s help to create a climate where information is shared Execution time of printf s c s c c c Hello World r n standard 8051 22 1184 MHz empty putchar Execution time of printf d 12345 standard 8051 22 1184 MHz empty putchar 3 printf_tiny integer speed is data dependent worst case is 0 33 ms 4Execution time of printf ld 123456789 standard 8051 E 22 1184 MHz empty putchar Execution time of printf 3f 12345 678 standard 8051 22 1184 MHz empty putchar 54 3 18 MEMORY MODELS CHAPTER 3 USING SDCC 3 18 Memory Models 3 18 1 MCS51 Memory Models 3 18 1 1 Small Medium Large and Huge SDCC allows four memory models fo
124. list see sdcc help debug xtra emit debug info in assembly output no pcode opt disable slightly faulty optimization on pCode stack loc sets the lowest address of the argument passing stack defaults to a suitably large shared databank to reduce BANKSEL overhead stack size sets the size if the argument passing stack default 16 minimum 4 4 5 6 Environment Variables The PIC14 port recognizes the following environment variables SDCC_PIC14_SPLIT_LOCALS Tf set and not empty sdcc will allocate each temporary register the ones called rOxNNNN in a section of its own By default if this variable is unset sdcc tries to cluster registers in sections in order to reduce the BANKSEL overhead when accessing them 4 5 7 The Library The PIC14 library currently only contains support routines required by the compiler to implement multiplication division and floating point support No libc like replacement is available at the moment though many of the common sdcc library sources in device 1ib should also compile with the PIC14 port 4 5 7 1 error missing definition for symbol __ gptrget1 The PIC14 port uses library routines to provide more complex operations like multiplication division modulus and generic pointer dereferencing In order to add these routines to your project you must link with PIC14 s libsdcc lib For single source file projects this is done automatically more complex projects must add libsdcc lib t
125. ly of processors mgbz80 Generate code for the GameBoy Z80 processor Not actively maintained mpicl4 Generate code for the Microchip PIC 14 bit processors p16f84 and variants In development not complete mpicl6 Generate code for the Microchip PIC 16 bit processors p18f452 and variants In development not complete mtlcs900h Generate code for the Toshiba TLCS 900H processor Not maintained not complete mxa51 Generate code for the Phillips XA51 processor Not maintained not complete SDCC inspects the program name it was called with so the processor family can also be selected by renaming the sdcc binary to f e z80 sdcc or by calling SDCC from a suitable link Option m has higher priority than setting from program name 3 2 2 Preprocessor Options SDCC uses an adapted version of the GNU Compiler Collection preprocessor cpp gcc http gcc gnu org If you need more dedicated options than those listed below please refer to the GCC CPP Manual at http www gnu org software gcc onlinedocs I lt path gt The additional location where the preprocessor will look for lt h gt or h files D lt macro value gt Command line definition of macros Passed to the preprocessor M Tell the preprocessor to output a rule suitable for make describing the dependencies of each object file For each source file the preprocessor outputs one make rule whose target is the object file name for that source file and whose depend
126. ly throughout the code generator So its use is not advised Also there are some other points that need special care 1 Do not create stack sections with size more than one physical bank that is 256 bytes 2 Stack sections should no cross physical bank limits i e pragma stack 0x50 0x 100 These limitations are caused by the fact that only FSRxL is modified when using SMALL stack model so no more than 256 bytes of stack can be used This problem will disappear after LARGE model is fully implemented 4 6 13 Functions In addition to the standard SDCC function keywords PIC16 port makes available two more wparam Use the WREG to pass one byte of the first function argument This improves speed but you may not use this for functions with arguments that are called via function pointers otherwise the first byte of the first parameter will get lost Usage void func_wparam int a wparam WREG hold the lower part of a x the high part of a is stored in FSR2 2 or 3 for large stack model shadowregs When entering exiting an ISR it is possible to take advantage of the PIC18F hardware shadow regis ters which hold the values of WREG STATUS and BSR registers This can be done by adding the keyword shadowregs before the interrupt keyword in the function s header void isr_shadow void shadowregs interrupt 1 shadowregs instructs the code generator not to store restore WREG STATUS BSR when entering exiting the IS
127. makebin Intl Hex to binary and GameBoy binay format converter sdcc bin as2gbmap py sdas map to rrgb map and no gmb sym file format converter sdcc support scripts 6 3 Documentation included in the distribution Subject Title Filename Where to get SDCC Compiler User Guide You re reading it right now online at http sdcc sourceforge net doc sdccman pdf Changelog of SDCC sdcc Changelog online at http sdcc svn sourceforge net viewvc checkout sdcc trunk sdcc ChangeLog ASXXXX Assemblers and sdcc sdas doc asxhtm html online at ASLINK Relocating Linker http sdcc svn sourceforge net viewvc hem checkout sdcc trunk sdcc sdas doc asxhtm SDCC regression test spec paf sdcc doc test_suite_spec pdf http sdcc sourceforge net doc test_suite_ online at Various notes dec doc tip sdec svn sou runk sdce doc te online at rceforge net viewvc sdcc Notes on debugging with SDCDB 2 a cc debugger README Etp sdes svn son checkoutx sdcc tru y rceforge net viewvc online at nk sdcc debugger README uCsim Software simulator for microcon trollers Dn http sded 6viusou checkoutx sdcc tru index html dcc sim ucsim doc index html rceforge net viewvc online at nk sdcc sim ucsim doc Temporary notes on the pic16 port sdec src picl6 NOTES http sdcc svn sou checkoutx sdcc tru rceforge net viewvc online at nk
128. mbler code _bp is the stack frame pointer and is used to compute the offset into the stack for parameters and local variables 51 3 15 INT 16 BIT AND LONG 32 BIT SUPPORT CHAPTER 3 USING SDCC 3 15 int 16 bit and long 32 bit Support For signed amp unsigned int 16 bit and long 32 bit variables division multiplication and modulus operations are implemented by support routines These support routines are all developed in ANSI C to facilitate porting to other MCUs although some model specific assembler optimizations are used The following files contain the described routines all of them can be found in lt installdir gt share sdcc lib Function Description _mulint c 16 bit multiplication _divsint c signed 16 bit division calls _divuint _divuint c unsigned 16 bit division _modsint c signed 16 bit modulus calls _moduint _moduint c unsigned 16 bit modulus _mullong c 32 bit multiplication _divslong c signed 32 division calls _divulong _divulong c unsigned 32 division _modslong c signed 32 bit modulus calls _modulong _modulong c unsigned 32 bit modulus Since they are compiled as non reentrant interrupt service routines should not do any of the above operations If this is unavoidable then the above routines will need to be compiled with the stack auto option after which the source program will have to be compiled with int long reent option Notice that you d
129. mpiled into the compiler additional rules may be added with the peep file lt filename gt option The rule language is best illustrated with examples replace mov Sl a mov a 1 by mov Sl a The above rule will change the following assembly sequence mov rl a mov a rl to mov rl a Note All occurrences of a n pattern variable must denote the same string With the above rule the assembly sequence mov rl a mov a r2 will remain unmodified Other special case optimizations may be added by the user via peep file option E g some variants of the 8051 MCU allow only a jmp and aca11 The following two rules will change all 13mp and 1ca11 to ajmp and acall replace lcall 1 by acall 1 replace ljmp 1 by ajmp 1 NOTE from version 2 7 3 on you can use option acall ajmp which also takes care of aligning the interrupt vectors properly The inline assembler code is also passed through the peep hole optimizer thus the peephole optimizer can also be used as an assembly level macro expander The rules themselves are MCU dependent whereas the rule language infra structure is MCU independent Peephole optimization rules for other MCU can be easily programmed using the rule language The syntax for a rule is as follows rule replace restart lt assembly sequence gt n e Sd by ce EA Xp lt assembly sequence gt n 137 if lt functionName gt n
130. n about f e Z80 PIC14 PIC16 and HC08 e There are many references pointing away from this documentation Don t let this distract you If there f e was a reference like http www opencores org together with a statement some processors which are targetted by SDCC can be implemented in a field programmable gate array or http sf net projects fpgac have you ever heard of an open source compiler that compiles a subset of C for an FPGA we expect you to have a quick look there and come back If you read this you are on the right track e Some sections attribute more space to problems restrictions and warnings than to the solution The installation section and the section about the debugger is intimidating e There are still lots of typos and there are more different writing styles than pictures 2 7 Testing the SDCC Compiler The first thing you should do after installing your SDCC compiler is to see if it runs Type Sdcc version at the prompt and the program should run and output its version like SDCC mcs51 z80 avr ds390 picl6 picl4 ds400 hc08 2 5 6 4169 May 8 2006 UNIX If it doesn t run or gives a message about not finding sdcc program then you need to check over your instal lation Make sure that the sdcc bin directory is in your executable search path defined by the PATH environment setting see section 2 8 Install trouble shooting for suggestions Make sure that the sdcc program is in the bin folder if not
131. nation The compiler does local and global common subexpression elimination e g i x y 1 Ji ot Y will be translated to iTemp x y i iTemp 1 j iTemp Some subexpressions are not as obvious as the above example e g a gt b i c 10 a gt b i d 11 In this case the address arithmetic a gt b i will be computed only once the equivalent code in C would be iTemp a gt b il iTemp c 10 iTemp d 11 The compiler will try to keep these temporary variables in registers 8 1 2 Dead Code Elimination int global void f inti ists x dead store global 1 dead store x global 2 return global 3 unreachable x will be changed to 91 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA int global void f global 2 8 1 3 Copy Propagation int int iy Jy i 10 j 1 return j will be changed to Int E 4 int ip je i 10 j 10 return 10 Note the dead stores created by this copy propagation will be eliminated by dead code elimination 8 1 4 Loop Optimizations Two types of loop optimizations are done by SDCC loop invariant lifting and strength reduction of loop induction variables In addition to the strength reduction the optimizer marks the induction variables and the register allocator tries to keep the induction variables in registers for the duration of the loop Because of this preferenc
132. nclude_dir_suffix environment variable see table below lib_dir_suffix environment variable see table below non free lib dir suffix environment variable see table below sdecconf_h_dir_separator environment variable either or makes sense here This character will only be used in sdecconf h don t forget it s a C header therefore a double backslash is needed there disable mcs5 1 port Excludes the Intel mcs51 port disable gbz80 port Excludes the GameBoy gbz80 port disable z80 port Excludes the z80 port disable avr port Excludes the AVR port disabled by default disable ds390 port Excludes the DS390 port disable hc08 port Excludes the HC08 port disable pic port Excludes the PIC14 port disable pic16 port Excludes the PIC16 port 2 1 CONFIGURE OPTIONS CHAPTER 2 INSTALLING SDCC disable xaS 1 port Excludes the XA51 port disabled by default disable ucsim Disables configuring and building of ucsim disable device lib Disables automatically building device libraries disable packihx Disables building packihx enable doc Build pdf html and txt files from the lyx sources enable libgc Use the Bohem memory allocator Lower runtime footprint without ccache Do not use ccache even if available Furthermore the environment variables CC CFLAGS the tools and their arguments can be influenced Please see configure help and the man info pages of configure for details The names of the s
133. nctions that make heavy use of bitfields i e 80 bytes of code space are saved when compiling malloc c with this option NO_REG_OPT Do not perform pCode registers optimization This should be used for debugging purposes If bugs in the pcode optimizer are found users can benefit from temporarily disabling the optimizer until the bug is fixed 66 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 4 Preprocessor Macros PIC16 port defines the following preprocessor macros while translating a source Macro Description SDCC_pic16 Port identification __picl6 Port identification same as above pic18fxxxx MCU Identification xxxx is the microcontrol identification number i e 452 6620 etc __18Fxxxx MCU Identification same as above STACK_MODEL_ nnn nnn SMALL or LARGE respectively according to the stack model used In addition the following macros are defined when calling assembler Macro Description __18Fxxxx MCU Identification xxxx is the microcontrol identification number i e 452 6620 etc SDCC_MODEL_nmm nnn SMALL or LARGE respectively according to the memory model used for SDCC STACK_MODEL_ nnn nnn SMALL or LARGE respectively according to the stack model used 4 6 5 Directories PIC16 port uses the following directories for searching header files and libraries Directory Description Target Command prefix PREFIX sdc
134. nd gawk exe One good place to get them is here http unxutils sourceforge net Download the file UnxUtils zip Now you have to install the utilities and setup MSVC so it can locate the required programs Here there are two alternatives choose one 1 The easy way a Extract UnxUtils zip to your C hard disk PRESERVING the original paths otherwise bison won t work If you are using WinZip make certain that Use folder names is selected b In the Visual C IDE click Tools Options select the Directory tab in Show directories for se lect Executable files and in the directories window add a new path C user local wbin click ok As a side effect you get a bunch of Unix utilities that could be useful such as diff and patch 2 A more compact way This one avoids extracting a bunch of files you may not use but requires some extra work 16 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC a Create a directory were to put the tools needed or use a directory already present Say for exam ple C util b Extract bison exe bison hairy bison simple flex exe and gawk exe to such directory WITHOUT preserving the original paths If you are using WinZip make certain that Use folder names is not selected c Rename bison exe to _bison exe d Create a batch file bison bat in CAutil and add these lines set BISON_SIMPLE C util bison simple set BISON_HAIRY C
135. nd new terms are printed in italic 1 4 Compatibility with previous versions Newer versions have usually numerous bug fixes compared with the previous version But we also sometimes introduce some incompatibilities with older versions Not just for the fun of it but to make the compiler more stable efficient and ANSI compliant see section 8 2 for ANSI Compliance e short is now equivalent to int 16 bits it used to be equivalent to char 8 bits which is not ANSI compliant To maintain compatibility old programs may be compiled using the short is 8bits commandline option see 3 2 9 on page 32 the default directory for gcc builds where include library and documentation files are stored is now in usr local share e char type parameters to vararg functions are casted to int unless explicitly casted and std c89 and std c99 command line option are not defined e g char a 3 printf d c n a char a will push a as an int and as a char resp if std c89 and std c99 command line options are not defined will push a as two ints if std c89 or std c99 command line option is defined pointer type parameters to vararg functions are casted to generic pointers on harvard architectures e g mcs51 ds390 unless explicitly casted and std c89 and std c99 command line option are not defined e option regextend has been removed e option noregparms has been removed e option stack after data has been removed
136. nd project entry workspaces http www cmake org Wiki CmakeSdcce 6 6 Related documentation recommended reading Name Subject Title Where to get c refcard pdf C Reference Card 2 pages https refcards com refcards c index html c faq C FAQ http www c faq com ISO IEC 9899 TC2 C Standard http www open std org jtcl sc22 wg14 www standards html 9899 ISO IEC DTR 18037 Extensions for Embedded C http www open std org jtcl sc22 wg14 www docs n1021 pdf Latest datasheet of target CPU vendor Revision history of datasheet vendor 6 7 Application notes specifically for SDCC SDCC makes no claims about the completeness of this list and about up to dateness or correctness of the application notes 86 6 8 SOME QUESTIONS CHAPTER 6 TIPS Vendor Subject Title Where to get Maxim Dallas Using the SDCC Compiler for the http pdfserv maxim ic com en an AN3346 pdf DS80C400 Maxim Dallas Using the Free SDCC C Compiler to http pdfserv maxim ic com en an AN3477 paf Develop Firmware for the DS89C420 430 440 450 Family of Microcontrollers Silicon Laboratories Integrating SDCC 8051 Tools Into The http www silabs com public documents tpub_doc Cygnal Silicon Labs IDE anote Microcontrollers en an1l98 pdf Ramtron Goal Semi Interfacing SDCC to Syn and Textpad http www ramtron com doc Produc
137. ned char spi_io unsigned char out_byte unsigned char i 8 do MOSI out_byte amp 0x80 out_byte lt lt 1 MCIK 1 _ asm nop __endasm x for slow peripherals x if MISO out_byte 1 MCLK 0 while 1 return out_byte Then someplace in the code for the first hardware you would use _ bit _ at 0x80 MOSI x I O port 0 bit 0 x bit _ at 0x81 MISO x I O port 0 bit 1 x _bit_ at 0x82 MCLK x I O port 0 bit 2 x 38 3 7 PARAMETERS amp LOCAL VARIABLES CHAPTER 3 USING SDCC Similarly for the second hardware you would use _bit_ at 0x83 MOSI x I O port 0 bit 3 x _bit_ at 0x91 MISO x I O port 1 bit 1 x _bit_ at 0x92 MCLK x I O port 1 bit 2 x and you can use the same hardware dependent routine without changes as for example in a library This is somehow similar to sbit but only one absolute address has to be specified in the whole project 3 7 Parameters amp Local Variables Automatic local variables and parameters to functions can either be placed on the stack or in data space The default action of the compiler is to place these variables in the internal RAM for small model or external RAM for medium or large model This in fact makes them similar to static so by default functions are non reentrant They can be placed on the stack by using the stack auto option by using pragma stackauto or by using the reentrant keyword in the function declaration
138. ng bugs http sourceforge net tracker group_id 599 amp atid 100599 With SDCC on average having more than 200 downloads on sourceforge per day there must be some users So it s not exactly easy to find a new bug If you find one we need it reporting bugs is good 1220 daily downloads on average Jan Sept 2006 and about 150 daily downloads between 2002 and 2005 This does not include other methods of distribution 88 7 2 REQUESTING FEATURES CHAPTER 7 SUPPORT 7 2 Requesting Features Like bug reports feature requests are forwarded to the developer mailing list This is the link for requesting features http sourceforge net tracker group_id 599 amp satid 350599 7 3 Submitting patches Like bug reports contributed patches are forwarded to the developer mailing list This is the link for submitting patches http sourceforge net tracker group_id 599 amp atid 300599 You need to specify some parameters to the diff command for the patches to be useful If you modified more than one file a patch created fe with diff Naur unmodified_directory modi fied_directory gt my_changes patch will be fine otherwise diff u sourcefile c orig sourcefile c gt my_changes patch will do 7 4 Getting Help These links should take you directly to the Mailing lists http sourceforge net mail group_id 599 and the Forums http sourceforge net forum group_id 599 lists and forums are archived and searchable so if you are lu
139. nough for many programs One must take care that when there are many levels of function nesting or there is excessive usage of stack its size should be extended An example of such a case is the printf sprintf family of functions If you encounter problems like not being able to print integers then you need to set the stack size around the maximum 256 for small stack model The following diagram shows what happens when calling printf to print an integer printf gt ltoa gt ultoa gt divschar It is should be understood that stack is easily consumed when calling complicated functions Using command line arguments like fomit frame pointer might reduce stack usage by not creating unnecessery stack frames Other ways to reduce stack usage may exist 4 6 19 Known Bugs 4 6 19 1 Extended Instruction Set The PIC16 port emits code which is incompatible with the extended instruction set available with many newer devices Make sure to always explicitly disable it usually using static _ code char __at __CONFIG4L conf41 more flags amp _XINST_OFF_4L Some devices namely 18f2455 18f2550 18f4455 and 18f4550 use _ENHCPU_OFF_4L instead of _XINST_OFF_4L 4 6 19 2 Regression Tests The PIC16 port currently passes most but not all of the tests in SDCC s regression test suite see section 7 8 thus no automatic regression tests are currently performed for the PIC16 target 75 Chapter 5 Debugging There are
140. ns nogcse Will not do global subexpression elimination this option may be used when the compiler creates undesirably large stack data spaces to store compiler temporaries spill locations sloc A warning message will be generated when this happens and the compiler will indicate the number of extra bytes it allocated It is recommended that this option NOT be used pragma nogcse can be used to turn off global subexpression elimination for a given function only noinvariant Will not do loop invariant optimizations this may be turned off for reasons explained for the previ ous option For more details of loop optimizations performed see Loop Invariants in section 8 1 4 It is recommended that this option NOT be used pragma noinvariant can be used to turn off invariant optimizations for a given function only noinduction Will not do loop induction optimizations see section strength reduction for more details It is recommended that this option is NOT used pragma noinduction can be used to turn off induction optimizations for a given function only nojtbound Will not generate boundary condition check when switch statements are implemented using jump tables See section 8 1 7 Switch Statements for more details It is recommended that this option is NOT used pragma nojtbound can be used to turn off boundary checking for jump tables for a given function only noloopreverse Will not do loop reversal optimization nolabelopt Will no
141. nted to it The linker is invoked from SDCC using a script file with extension Ink You can view this file to troubleshoot linking problems such as those arising from missing libraries 3 1 4 Projects with Additional Libraries Some reusable routines may be compiled into a library see the documentation for the assembler and linkage editor which are in lt installdir gt share sdcc doc for how to create a lib library file Libraries created in this manner can be included in the command line Make sure you include the L lt library path gt option to tell the linker where to look for these files if they are not in the current directory Here is an example assuming you have the source file foomain c and a library foolib lib in the directory mylib if that is not the same as your current project sdcc foomain c foolib lib L mylib Note here that mylib must be an absolute path name The most efficient way to use libraries is to keep separate modules in separate source files The lib file the command backfills unused memory with 0x12 and the overall 16 bit sum of the complete 64 kByte block is zero If the program counter on an mcs51 runs wild the backfill pattern 0x12 will be interpreted as an 1ca11 to address 0x1212 where an emergency routine could sit 23 3 1 COMPILING CHAPTER 3 USING SDCC now should name all the modules rel files For an example see the standard library file libsdcc lib in the directory lt installdir gt sha
142. ntf tiny USE_FLOATS 1 filename printf_large c printf_large c printfl c printf_fast c printf_fast_f c printf_tiny c Hello World size 1 7k 2 4k 4 3k 5 6k 1 2k 1 8k 1 3k 1 3k 1 9k 1 9k 0 44k 0 44k small large code size small large 0 47k _ltoa 1 4k 2 0k 2 8k 3 7k 0 45k 1 2k 1 2k 1 6k 1 6k 0 26k 0 26k string speed small large 1 52 2 59 ms 1 53 2 62 0 92 0 93 0 45 0 45 ms 0 46 0 46 0 45 0 45 ms ms ms ms f T2 ci 3 01 3 61 ms 3 01 3 61 3 51 0 22 0 22ms 0 23 0 23 0 25 0 25 ms small large ms 18 13 ms ms 14 long speed 5 37 631ms 5 37 631 8 71 0 40 0 40ms 0 40 0 40 small large ms 40 65 ms ms 15 float speed a 7 49 122 47 4 a 1 04 1 04 small large ms ms 3 17 2 2 lt malloc h gt As of SDCC 2 6 2 you no longer need to call an initialization routine before using dynamic memory allocation and a default heap space of 1024 bytes is provided for malloc to allocate memory from If you need a different heap size you need to recompile _heap c with the required size defined in HEAP_SIZE It is recommended to make a copy of this file into your project directory and compile it there with sdcc c _heap c D HEAP_SIZE 2048 And then link it with sdcc main rel _heap rel 3 17 3 Math functions sinf powf sqrtf etc 3 17 3 1 lt math h gt See definitions in file lt math h gt 3 17 4 Other
143. number on page 57 in section3 19 Note this functionality is not in conformance with C99 standard Wp preprocessorOption preprocessorOption Pass the preprocessorOption to the preprocessor sdcpp 26 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC 3 2 3 Linker Options L lib path lt absolute path to additional libraries gt This option is passed to the linkage editor s additional libraries search path The path name must be absolute Additional library files may be specified in the command line See section Compiling programs for more details xram loc lt Value gt The start location of the external ram default value is 0 The value entered can be in Hex adecimal or Decimal format e g xram loc 0x8000 or xram loc 32768 code loc lt Value gt The start location of the code segment default value 0 Note when this option is used the interrupt vector table is also relocated to the given address The value entered can be in Hexadecimal or Decimal format e g code loc 0x8000 or code loc 32768 stack loc lt Value gt By default the stack is placed after the data segment Using this option the stack can be placed anywhere in the internal memory space of the 8051 The value entered can be in Hexadecimal or Decimal format e g stack loc 0x20 or stack loc 32 Since the sp register is incremented before a push or call the initial sp will be set to one byte prior the provided value The provided value should not o
144. o any validation of the code within the __asm __endasm keyword pair Specifically it will not know which registers are used and thus register pushing popping has to be done manually It is recommended that each assembly instruction including labels be placed in a separate line as the example shows When the peep asm command line option is used the inline assembler code will be passed through the peephole optimizer There are only a few if any cases where this option makes sense it might cause some unexpected changes in the inline assembler code Please go through the peephole optimizer rules defined in file SDCCpeeph def before using this option 3 13 2 Naked Functions A special keyword may be associated with a function declaring it as _naked The _naked function modifier attribute prevents the compiler from generating prologue and epilogue code for that function This means that the user is entirely responsible for such things as saving any registers that may need to be preserved selecting the proper register bank generating the return instruction at the end etc Practically this means that the contents of the function must be written in inline assembler This is particularly useful for interrupt functions which can have a large and often unnecessary prologue epilogue For example compare the code generated by these two functions volatile data unsigned char counter void simplelnterrupt void __interrupt 1 counter
145. o the linker s arguments Make sure you also add an include path for the library using the I switch to the linker 4 5 7 2 Processor mismatch in file XXX This warning can usually be ignored due to the very good compatibility amongst 14 bit PIC devices You might also consider recompiling the library for your specific device by changing the ARCH p16f877 default target entry in device lib pic Makefile in and device lib pic Makefile to reflect your device This might even improve performance for smaller devices as unnecessary BANKSELs might be removed 4 5 8 Known Bugs 4 5 8 1 Function arguments Functions with variable argument lists like printf are not yet supported Similarly taking the address of the first argument passed into a function does not work It is currently passed in WREG and has no address 4 5 8 2 Regression tests fail Though the small subset of regression tests in src regression passes SDCC regression test suite does not indicating that there are still major bugs in the port However many smaller projects have successfully used SDCC in the past 64 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 The PIC16 port The PIC16 port adds support for Microchip PIC MCUs with 16 bit wide instructions Currently this family of microcontrollers contains the PIC18Fxxx and PIC18Fxxxx devices supported by the port include 18F 242 248 252 258 442 448 452 458 18F 1220 132
146. ode page pic14 62 Command Line Options 25 Communication Bug report 88 Feature request 89 Forums 85 Mailing lists 85 89 Monitor 85 Patch submission 89 RSS feed 85 Trackers 85 wiki 85 Compatibility with previous versions 7 Compiler internals 103 compiler h include file 35 83 const 32 Copy propagation 92 cpp see sdcpp see sdcpp critical 42 _ critical 42 cvs see Subversion Cyclomatic complexity 31 101 d52 86 d52 disassembler 86 data hc08 storage class 37 __data hc08 storage class 37 data mcs51 ds390 storage class 27 33 36 __data mcs51 ds390 storage class 33 36 DDD debugger 80 86 Dead code elimination 32 91 107 112 INDEX INDEX Debugger 22 77 defines 59 Defines created by the compiler 59 DESTDIR 13 Division 39 41 Documentation 18 84 double not supported 100 download 88 doxygen source documentation tool 86 DPTR 50 60 96 DPTR DPH DPL 50 DS390 28 Options model flat24 28 protect sp update 28 stack 10bit 28 stack probe 28 tini libid 28 use accelerator 28 __ds390 59 DS390 memory model 55 DS400 61 DS80C390 25 DS80C400 25 61 87 DS89C4x0 87 dynamic memory allocation malloc 54 ELF format 27 Emacs 80 __endasm 47 49 _endasm 42 47 49 Endianness 83 96 Environment variables 33 Examples 90 External stack mcs51 55 far storage class 34 46 __ far storage class
147. ommended way would be to copy crtstart asm f e from http sdcc svn sourceforge net viewvc x checkoutx sdcc trunk sdcc device lib mcs51 crtstart asm into the source directory adapt it there then assemble it with sdas8051 plosgff gt crtstart asm and when linking your project explicitly specify crtstart rel As a bonus a listing of the relocated object file crtstart rst is generated 3 12 2 HC08 Startup Code The HCO8 startup code follows the same scheme as the MCS51 startup code 3 12 3 Z80 Startup Code On the Z80 the startup code is inserted by linking with crt0 rel which is generated from sdcc device lib z80 crt0 s If you need a different startup code you can use the compiler option no std crtO and provide your own crt0 rel 3 13 Inline Assembler Code 3 13 1 A Step by Step Introduction Starting from a small snippet of c code this example shows for the MCS51 how to use inline assembly access variables a function parameter and an array in xdata memory The example uses an MCS51 here but is easily adapted for other architectures This is a buffer routine which should be optimized far __at 0x7f00 buf 0x100 unsigned char head tail x if interrupts are involved see unsigned char section 3 9 1 1 about volatile void to_buffer unsigned char c if head unsigned char tail 1 cast neededto avoid promotion to integer buf head c access to a 256 byte aligned array If the code snipp
148. ompiler installation which also builds and installs the debugger in the target directory specified during configuration The debugger allows you debug BOTH at the C source and at the ASM source level 5 1 1 Compiling for Debugging The debug option must be specified for all files for which debug information is to be generated The compiler generates a adb file for each of these files The linker creates the cdb file from the adb files and the address information This cdb is used by the debugger 5 1 2 How the Debugger Works When the debug option is specified the compiler generates extra symbol information some of which are put into the assembler source and some are put into the adb file Then the linker creates the cdb file from the individual adb files with the address information for the symbols The debugger reads the symbolic information generated by the compiler amp the address information generated by the linker It uses the SIMULATOR Daniel s S51 to execute the program the program execution is controlled by the debugger When a command is issued for the debugger it translates it into appropriate commands for the simulator Currently SDCDM only connects to the simulator but newcdb at http ec2drv sf net is an effort to connect directly to the hardware 5 1 3 Starting the Debugger SDCDB The debugger can be started using the following command line Assume the file you are debugging has the file name foo sdcdb foo
149. on t have to call these routines directly The compiler will use them automatically every time an integer operation is required 3 16 Floating Point Support SDCC supports IEEE single precision 4 bytes floating point numbers The floating point support routines are derived from gcc s floatlib c and consist of the following routines Function Description _fsadd c add floating point numbers _fssub c subtract floating point numbers _fsdiv c divide floating point numbers _fsmul c multiply floating point numbers _fs2uchar c convert floating point to unsigned char _fs2char c convert floating point to signed char _fs2uint c convert floating point to unsigned int _fs2int c convert floating point to signed int _fs2ulong c convert floating point to unsigned long _fs2long c convert floating point to signed long _uchar2fs c convert unsigned char to floating point _char2fs c convert char to floating point number _uint2fs c convert unsigned int to floating point _int2fs c convert int to floating point numbers _ulong2fs c convert unsigned long to floating point number _long2fs c convert long to floating point number These support routines are developed in ANSI C so there is room for space and speed improvement Note if all these routines are used simultaneously the data space might overflow For serious floating point usage the large model might be needed Also notice that y
150. on to the assembler See file sdcc sdas doc asxhtm html for assembler options cd 31 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC std sdcc89 Generally follow the C89 standard but allow SDCC features that conflict with the standard default std c89 Follow the C89 standard and disable SDCC features that conflict with the standard std sdcc99 Generally follow the C99 standard but allow SDCC features that conflict with the standard incom plete support std c99 Follow the C99 standard and disable SDCC features that conflict with the standard incomplete sup port codeseg lt Name gt The name to be used for the code segment default CSEG This is useful if you need to tell the compiler to put the code in a special segment so you can later on tell the linker to put this segment in a special place in memory Can be used for instance when using bank switching to put the code in a bank constseg lt Name gt The name to be used for the const segment default CONST This is useful if you need to tell the compiler to put the const data in a special segment so you can later on tell the linker to put this segment in a special place in memory Can be used for instance when using bank switching to put the const data in a bank fdollars in identifiers Permit as an identifier character more pedantic Actually this is not a SDCC compiler option but if you want more warnings you can use a sepa rate tool dedicated to syn
151. ou don t have to call this routines directly The compiler will use them automatically every time a floating point operation is required These floating point routines not sinf cosf for the mcs51 are implemented in assembler 52 3 17 LIBRARY ROUTINES CHAPTER 3 USING SDCC 3 17 Library Routines lt pending this is messy and incomplete a little more information is in sdcc doc libdoc txt gt 3 17 1 Compiler support routines _gptrget _mulint etc 3 17 2 Stdclib functions puts printf strcat etc 3 17 2 1 lt stdio h gt getchar putchar As usual on embedded systems you have to provide your own getchar and putchar routines SDCC does not know whether the system connects to a serial line with or without handshake LCD keyboard or other device And whether a 1f to crlf conversion within putchar is intended You ll find examples for serial routines f e in sdcc device lib For the mcs51 this minimalistic polling putchar routine might be a start void putchar char c while TI x assumes UART is initialized x r TI 0 SBUF c printfO The default printf implementation in printf_large c does not support float except on ds390 only lt NO FLOAT gt will be printed instead of the value To enable floating point output recompile it with the option DUSE_FLOATS 1 on the command line Use model large for the mcs51 port since this uses a lot of memory To enable float support for t
152. ourcefile map The memory map for the load module created by the Linker sourcefile mem A file with a summary of the memory usage sourcefile ihx The load module in Intel hex format you can select the Motorola S19 format with out fmt s19 If you need another format you might want to use Objdump or srecord see also section 3 1 2 Both formats are documented in the documentation of srecord sourcefile adb An intermediate file containing debug information needed to create the cdb file with debug sourcefile cdb An optional file with debug containing debug information The format is documented in cdbfileformat pdf sourcefile no extension An optional AOMF or AOMFS51 file containing debug information generated with option debug The Intel absolute object module format is a subformat of the OMF51 format and is commonly used by third party tools debuggers simulators emulators sourcefile dump Dump file to debug the compiler it self generated with option dumpall see section 3 2 10 and section 9 1 Anatomy of the compiler 3 1 2 Postprocessing the Intel Hex file In most cases this won t be needed but the Intel Hex file which is generated by SDCC might include lines of varying length and the addresses within the file are not guaranteed to be strictly ascending If your toolchain or a bootloader does not like this you can use the tool packihx which is part of the SDCC distribution packihx sourcefile i
153. ov _p 1 a iTemp 10 Ir13 14 int r2 r3 iTemp7 119 13 _far int DPTR movx a dptr mov r2 a inc dptr movx a dptr mov 13 a GTemp6 Ir5 16 _near int r0 iTemp10 Ir13 14 int 12 13 mov r0 ar2 inc rO mov r10 ar3 iTemp6 Ir5 16 _near int r0 iTemp6 Ir5 16 _near int r0 Ox2 short inc rO goto _whilecontinue_0 1 sjmp 00101 _whilebreak_0 3 00103 iTemp2 Ir18 40 short 12 0x0 short mov r2 0x00 iTemp11 Ir19 40 short r3 0x0 short mov r3 0x00 Temp21 1r21 38 short r4 0x0 short mov r4 0x00 iTemp23 lr22 38 int r5 r6 Oxa int mov r5 0x0A mov r6 0x00 iTemp17 lr23 38 int r7 r0 Oxle int mov r7 0x1E mov r0 0x00 forcond_0 4 00104 Temp13 1r25 26 char CC iTemp21 1r21 38 short r4 lt Oxa short if iTemp13 lr25 26 char CC 0 goto _forbreak_0 7 clr c mov a r4 xrl a 0x80 subb a 0x8a jnc 00107 00115 iTemp2 Ir18 40 short r2 iTemp2 1r18 40 short r2 Temp21 Ir21 38 short r4 mov a r4 add a r2 mov r2 a iTemp15 lr29 30 short r1 iTemp21 lr21 38 short r4 0x3 short mov b 0x03 mov a r4 mul ab mov rl a iTemp11 lr19 40 short r3 iTemp11 Ir19 40 short 13 iTemp15 1r29 30 short 11 add a r3 mov r3 a iTemp17 1r23 38 int 17 r0 iTemp17 Ir23 38 int r7 r0 0x3 short mov a r7 add a 0xfd mov 17 a mov a r0 addc a H
154. ov a _gint 1 000C 23 63 rl a 000D 54 01 64 anl a 0x01 000F F5x x02 65 mov foo_hob1_1_1 a 66 hob c 8 0011 E5x01 67 mov a _gint 1 0013 33 68 rlc a 0014 92x00 69 mov foo hob2 1_1 e 66 hob c 9 0016 E5x01 67 mov a _gint 1 0018 33 68 rle a 0019 92x01 69 mov foo_hob3_1_1 c 70 hob c 10 001B E5x01 71 mov a _gint 1 001D 03 72 Lx a 001E 54 01 73 anl a 0x01 0020 F5x 03 74 mov foo_aob1_1_1 a Usually 8 bit processors don t care much about endianness This is not the case for the standard 8051 which only has an instruction to increment its dptr datapointer so little endian is the more efficient byte order 96 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA 75 hob c 11 0022 E5x01 76 mov a _gint 1 0024 13 77 Tre a 0025 92x02 78 mov foo_aob2_1_1 c 79 hob c 12 0027 E5x01 80 mov a _gint 1 0029 A2 E3 81 mov c acc 3 002B 92x03 82 mov foo_aob3_1_1 c Other variations of these cases however will not be recognized They are standard C expressions so I heartily recommend these be the only way to get the highest order bit it is portable Of course it will be recognized even if it is embedded in other expressions e g xyz gint gint gt gt 15 1 will still be recognized 8 1 12 Higher Order Byte Higher Order Word It is also frequently required to obtain a higher order byte or word of a larger integral type long int or short types SDCC r
155. perhaps something did not install correctly SDCC is commonly installed as described in section Install and search paths Make sure the compiler works on a very simple example Type in the following test c program using your favorite ASCII editor Tf you should know why please drop us a note 2 8 INSTALL TROUBLE SHOOTING CHAPTER 2 INSTALLING SDCC char test void main void test 0 Compile this using the following command sdcc c test c If all goes well the compiler will generate a test asm and test rel file Congratulations you ve just compiled your first program with SDCC We used the c option to tell SDCC not to link the generated code just to keep things simple for this step The next step is to try it with the linker Type in sdcc test c If all goes well the compiler will link with the libraries and produce a test ihx output file If this step fails no test ihx and the linker generates warnings then the problem is most likely that SDCC cannot find the usr local share sdcc lib directory see section 2 8 Install trouble shooting for suggestions The final test is to ensure SDCC can use the standard header files and libraries Edit test c and change it to the following include lt string h gt char str1 10 void main void strcpy strli testing Compile this by typing sdcc test c This should generate a test ihx output file and it should give no warnings such as not finding th
156. ports there and have an overview about the known bugs Bug reports are automatically forwarded to the developer mailing list and will be fixed ASAP When reporting a bug it is very useful to include a small test program the smaller the better which reproduces the problem If you can isolate the problem by looking at the generated assembly code this can be very helpful Compiling your program with the dumpall option can sometimes be useful in locating optimization problems When reporting a bug please make sure you 1 Attach the code you are compiling with SDCC 2 Specify the exact command you use to run SDCC or attach your Makefile 3 Specify the SDCC version type sdcc v your platform and operating system 4 Provide an exact copy of any error message or incorrect output 5 Put something meaningful in the subject of your message Please attempt to include these 5 important parts as applicable in all requests for support or when reporting any problems or bugs with SDCC Though this will make your message lengthy it will greatly improve your chance that SDCC users and developers will be able to help you Some SDCC developers are frustrated by bug reports without code provided that they can use to reproduce and ultimately fix the problem so please be sure to provide sample code if you are reporting a bug Please have a short check that you are using a recent version of SDCC and the bug is not yet known This is the link for reporti
157. quires the following steps 1 Create a new device description Each device is described in two files pic16f h and picl6f c These files primarily define SFRs structs to access their bits and symbolic configuration options Both files can be generated from gputils inc files using the perl script support scripts inc2h pl This file also contains further instructions on how to proceed 2 Copy the h file into SDCC s include path and either add the c file to your project or copy it to device lib pic libdev Afterwards rebuild and install the libraries 3 Edit picl4devices txt in SDCC s include path device include pic in the source tree or usr local share sdcc include pic after installation You need to add a device specification here to make the memory layout code banks RAM aliased memory regions known to the compiler Probably you can copy and modify an existing entry The file format is documented at the top of the file 4 5 3 Interrupt Code For the interrupt function use the keyword __interrupt with level number of 0 PIC14 only has 1 interrupt so this number is only there to avoid a syntax error it ought to be fixed E g void Intr void __interrupt 0 TOIF 0 Clear timer interrupt 4 5 4 Linking and Assembling For assembling you can use either GPUTILS gpasm exe or MPLAB s mpasmwin exe GPUTILS are available from http sourceforge net projects gputils For linking you can us
158. r MCS51 code small medium large and huge Modules compiled with different memory models should never be combined together or the results would be unpredictable The library routines supplied with the compiler are compiled as small medium and large The compiled library modules are contained in separate directories as small medium and large so that you can link to the appropriate set When the medium large or huge model is used all variables declared without a storage class will be allocated into the external ram this includes all parameters and local variables for non reentrant functions Medium model uses pdata and large and huge models use xdata When the small model is used variables without storage class are allocated in the internal ram The huge model compiles all functions as banked4 1 3 and is otherwise equal to large for now All other models compile the functions without bankswitching by default Judicious usage of the processor specific storage classes and the reentrant function type will yield much more efficient code than using the large model Several optimizations are disabled when the program is compiled using the large model it is therefore recommended that the small model be used unless absolutely required 3 18 1 2 External Stack The external stack xstack option is located in pdata memory usually at the start of the external ram segment and uses all unused space in pdata max 256 bytes When xstack option is
159. r and cannot be a return value from a function e g 99 8 2 ANSECOMPLIANCE CHAPTER 8 SDCC TECHNICAL DATA struct s 1 y Struct ssl s2 foo sl s2 x is invalid in SDCC although allowed in ANSI x struct s fool structs parms invalid in SDCC although allowed in ANSI x struct s rets return rets is invalid in SDCC although allowed in ANSI x e initialization of structure arrays must be fully braced struct s char x a 1 2 invalid in SDCC x struct s char x al 111 12 OK x e long long 64 bit integers not supported e double precision floating point not supported e Old K amp R style function declarations are NOT allowed foo 1 3 this old style of function declarations int i j is valid in ANSI but not valid in SDCC x e Some enhancements in C99 are not supported e g for int 1 0 1 lt 10 i is invalid in SDCC although allowed in C99 x e Certain words that are valid identifiers in the standard may be reserved words in SDCC unless the std c89 or std c99 command line options are used These may include depending on the selected processor at banked bit code critical data eeprom far flash idata interrupt near nonbanked pdata reentrant sbit sfr shadowregs sram using wparam xdata _overlay _a
160. r objects you need to tell the linker where to put your segments To do this you use the following command line option to SDCC Wl b BANK1 0x18000 See 3 2 3 This sets the virtual start address of this segment It sets the banknumber to 0x01 and maps the bank to 0x8000 and up The linker will not check for overflows again this is your responsibility 4 2 DS400 port The DS80C400 microcontroller has a rich set of peripherals In its built in ROM library it includes functions to access some of the features among them is a TCP stack with IP4 and IP6 support Library headers currently in beta status and other files are provided at ftp ftp dalsemi com pub tini ds80c400 c_libraries sdcc index html 4 3 The Z80 and gbz80 port SDCC can target both the Zilog Z80 and the Nintendo GameBoy s Z80 like gbz80 The Z80 port is passed through the same regressions tests see section 7 8 as the MCS51 and DS390 ports so floating point support support for long variables and bitfield support is fine See mailing lists and forums about interrupt routines As always the code is the authoritative reference see z80 ralloc c and z80 gen c The stack frame is similar to that generated by the IAR Z80 compiler IX is used as the base pointer HL and IY are used as a temporary 61 4 4 THE HC08 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS registers and BC and DE are available for holding variables Return values for the Z80 port are stored in L one by
161. re lib small 3 1 5 Using sdcclib to Create and Manage Libraries Alternatively instead of having a rel file for each entry on the library file as described in the preceding section sdcclib can be used to embed all the modules belonging to such library in the library file itself This results in a larger library file but it greatly reduces the number of disk files accessed by the linker Additionally the packed library file contains an index of all include modules and symbols that significantly speeds up the linking process To display a list of options supported by sdcclib type sdcclib To create a new library file start by compiling all the required modules For example sdcc c _divsint c sdcc c _divuint c sdcc c _modsint c sdcc c _moduint c sdcc c _mulint c This will create files _divsint rel _divuint rel _modsint rel _moduint rel and _mulint rel The next step is to add the rel files to the library file sdcclib libint lib _divsint rel sdcclib libint lib _divuint rel sdcclib libint lib _modsint rel sdcclib libint lib _moduint rel sdcclib libint lib _mulint rel Or if you preffer sdcclib libint lib divsint rel _divuint rel _modsint rel _moduint rel _mulint rel If the file already exists in the library it will be replaced If a list of rel files is available you can tell sdcclib to add those files to a library For example if the file myliblist txt contains _divsint rel _divuint rel _modsint rel
162. rget debugging stub which accepts only primitive commands Terms to enter into your favourite search engine could be remote debugging gdb stub or inferior debug ger is there one e use an on target hardware debugger Some of the more modern MCUs include hardware support for setting break points and monitoring changing variables by using dedicated hardware pins This facility doesn t require additional code to run on the target and usually doesn t affect runtime behaviour until a breakpoint is hit For the mcs51 most hardware debuggers use the AOMF file see 3 1 1 as input file Last not least e if you are not familiar with any of the following terms you re likely to run into problems rather sooner than later volatile atomic memory map overlay As an embedded programmer you have to know them so why not look them up before you have problems e tell someone else about your problem actually this is a surprisingly effective means to hunt down the bug even if the listener is not familiar with your environment As failure to communicate is probably one of the job induced deformations of an embedded programmer this is highly encouraged 5 1 Debugging with SDCDB SDCC is distributed with a source level debugger The debugger uses a command line interface the command repertoire of the debugger has been kept as close to gdb the GNU debugger as possible The configuration and build process is part of the standard c
163. rlay 39 41 56 pragma opt_code_balanced 57 pragma opt_code_size 57 pragma opt_code_speed 56 pragma pedantic_parse_number 57 pragma preproc_asm 57 pragma restore 56 58 pragma save 55 58 pragma sdcc_hash 58 pragma stackauto 39 56 pragma std_c89 57 pragma std_c99 57 pragma std_sdcc89 57 pragma std_sdcc99 57 Pragmas 55 Preprocessor 21 30 57 Options 26 PIC16 Macros 67 printfQ 53 54 floating point support 53 parameters 83 PIC16 74 PIC16 Floating point support 69 PIC16 floating point support 69 printf_fast mes51 53 printf_fast_f mcs51 53 printf_small 53 printf_tinyO mcs51 53 putchar 53 83 Processor selection options 25 project workspace 86 promotion to signed int 46 47 82 push pop 48 49 56 putchar 53 Quality control 89 reentrant 30 31 39 50 52 55 99 Register allocation 92 103 106 Register assignment 33 register bank mcs51 ds390 36 39 43 Regression test 61 84 89 90 Regression test PIC14 90 Regression test PIC16 75 Related tools 85 Release policy 89 Reporting bugs 88 Requesting features 9 89 return value 50 99 rotating bits 95 RSS feed 85 Runtime library 44 45 s51 simulator 21 sbit 8 35 __sbit 8 35 sdas sdasgb sdas6808 sdas8051 sdasz80 6 48 84 SDCC Defines SDCC version macro 59 SDCC_CHAR_UNSIGNED 59 SDCC_ds390 59 SDCC_FLOAT_REENT 59 SDCC_INT_LONG_REENT 59 SDCC_mes51 59 SD
164. rupt service routines to be coded in C with some extended keywords void timer_isr void __interrupt 1 _ using 1 The optional number following the interrupt keyword is the interrupt number this routine will service When present the compiler will insert a call to this routine in the interrupt vector table for the interrupt number specified If you have multiple source files in your project interrupt service routines can be present in any of them but a prototype of the isr MUST be present or included in the file that contains the function main The optional 8051 specific keyword using can be used to tell the compiler to use the specified register bank when generating code for this function Interrupt service routines open the door for some very interesting bugs 3 9 1 1 Common interrupt pitfall variable not declared volatile If an interrupt service routine changes variables which are accessed by other functions these variables have to be declared volatile See http en wikipedia org wiki Volatile variable 3 9 1 2 Common interrupt pitfall non atomic access If the access to these variables is not atomic i e the processor needs more than one instruction for the access and could be interrupted while accessing the variable the interrupt must be disabled during the access to avoid inconsistent data Access to 16 or 32 bit variables is obviously not atomic on 8 bit CPUs and should be protected by disabling interrupts You
165. s kept compatible 4 1 1 pdata access by SFR With the upcome of devices with internal xdata and flash memory devices using port P2 as dedicated I O port is becoming more popular Switching the high byte for pdata access which was formerly done by port P2 is then achieved by a Special Function Register In well established MCS51 tradition the address of this sfr is where the chip designers decided to put it Needless to say that they didn t agree on a common name either So that the startup code can correctly initialize xdata variables you should define an sfr with the name _XPAGE at the appropriate location if the default port P2 is not used for this Some examples are sfr at 0x85 _XPAGE Ramtron VRS51 family a k a MPAGE x sfr at 0x92 _XPAGE Cypress EZ USB family Texas Instruments Chipcon a k a MPAGE x sfr at 0x91 _XPAGE Infineon Siemens C500 family a k a XPAGE x r__ at Oxaf _XPAGE some Silicon Labs Cygnal chips a k a EMIOCN x r_at 0xaa _XPAGE some Silicon Labs Cygnal chips a k a EMIOCN x n There are also devices without anything resembling _XPAGE but luckily they usually have dual data pointers For these devices a different method can be used to correctly initialize xdata variables A default implementation is already in crtxinit asm but it needs to be assembled manually with DUAL_DPTR set to 1 For more exotic implementations further customization
166. s may be needed See section 3 12 for other possibilities 4 1 2 Other Features available by SFR Some MCS51 variants offer features like Dual DPTR multiple DPTR decrementing DPTR 16x16 Multiply These are currently not used for the MCS51 port If you absolutely need them you can fall back to inline assembly or submit a patch to SDCC 4 1 3 Bankswitching Bankswitching a k a code banking is a technique to increase the code space above the 64k limit of the 8051 60 4 2 DS400 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 1 3 1 Hardware 8000 FFFF bankl bank2 bank3 0000 7FFF common SiLabs C8051F120 example Usually the hardware uses some sfr an output port or an internal sfr to select a bank and put it in the banked area of the memory map The selected bank usually becomes active immediately upon assignment to this sfr and when running inside a bank it will switch out this code it is currently running Therefor you cannot jump or call directly from one bank to another and need to use a so called trampoline in the common area For SDCC an example trampoline is in crtbank asm and you may need to change it to your 8051 derivative or schematic The presented code is written for the C8051F120 When calling a banked function SDCC will put the LSB of the functions address in register RO the MSB in R1 and the bank in R2 and then call this trampoline __sdcc_banked_call The current selected bank is saved on the s
167. save registers when calling these functions extra code need to be manually inserted at the entry and exit for these functions to save and restore the regis ters used by these functions this can SUBSTANTIALLY reduce code and improve run time performance of the generated code In the future the compiler with inter procedural analysis may be able to determine the appropriate scheme to use for each function call If callee saves command line option is used see page on page 30 the function names specified in pragma callee_saves is appended to the list of functions specified in the command line exclude none acc b dpl dph The exclude pragma disables the generation of pairs of push pop in structions in nterrupt Service Routines The directive should be placed immediately before the ISR function definition and it affects ALL ISR functions following it To enable the normal register saving for ISR func tions use pragma exclude none See also the related keyword _naked less_pedantic the compiler will not warn you anymore for obvious mistakes you re on your own now See also the command line option less pedantic on page 31 More specifically the following warnings will be disabled comparison is always true false due to limited range of data type 94 overflow in implicit constant conversion 158 the in famous conditional flow changed by optimizer so said EVELYN the modified DOG 110 function function name must ret
168. sdcc src picl6 NOTES SDCC internal documentation debugging file sdcc doc cdbfileformat pdf format cdbfileformat pdf http sdcc sourceforge net doc online at 84 6 4 COMMUNICATION ONLINE AT SOURCEFORGE CHAPTER 6 TIPS 6 4 Communication online at SourceForge Note Link Subject Title wiki MERDE sdcc wiki sourceforge net sdcc user mailing list around 650 subscribers mid 2009 tes leis sourceforge net mailman listinfo sdcc user sdcc devel mailing list https lists sourceforge net mailman listinfo sdcc devel help forum similar scope as sdcc user mailing list http source forge net forum forum php forum_id 1865 open discussion forum http source forge net forum forum php forum_id 1864 trackers bug tracker feature requests patches support requests webdocs http source forge net tracker group_id 599 rss feed stay tuned with most not all sdcc activities http source rss2_keepsake forge net export php group_id 599 With a sourceforge account you can monitor forums and trackers so that you automatically receive mail on changes You can digg out earlier communication by using the search function http sourceforge net search group_id 599 6 5 Related open source tools 85 6 6 RELATED DOCUMENTATION RECOMMENDED READING
169. semble The output is an assembler code file for the input file specified int long reent Integer 16 bit and long 32 bit libraries have been compiled as reentrant Note by default these libraries are compiled as non reentrant See section Installation for more details cyclomatic This option will cause the compiler to generate an information message for each function in the source file The message contains some important information about the function The number of edges and nodes the compiler detected in the control flow graph of the function and most importantly the cyclomatic complexity see section on Cyclomatic Complexity for more details float reent Floating point library is compiled as reentrant See section Installation for more details funsigned char The default signedness for every type is signed In some embedded environments the default signedness of char is unsigned To set the signess for characters to unsigned use the option funsigned char If this option is set and no signedness keyword unsigned signed is given a char will be signed All other types are unaffected main return This option can be used if the code generated is called by a monitor program or if the main routine includes an endless loop This option results in slightly smaller code and saves two bytes of stack space The return from the main function will return to the function calling main The default setting is to lock upi e generatea
170. sembly code and insert an define USE_ASSEMBLY 1 and finally have unsigned char far __at 0x7f00 buf 0x100 unsigned char head tail define USE_ASSEMBLY 1 if USE_ASSEMBLY void to_buffer unsigned char c if head unsigned char tail 1 buf head c else void to_buffer unsigned char c c to avoid warning unreferenced function argument __asm Save used registers here If we were still using r2 r3 we would have to push them here if head unsigned char tail 1 mov a _tail dec a xrl a _head we could do an ANL a 0x0f here to use a smaller buffer see below JZ t_b_end Y buf head c mov a dpl dpl holds lower byte of function argument mov dpl _head buf is 0x100 byte aligned so head can be used directly mov dph _buf gt gt 8 47 3 13 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC movx dptr a inc _head we could do an ANL _head 0x0f here to use a smaller buffer see above t_b_ends restore used registers here _endasm tendif The inline assembler code can contain any valid code understood by the assembler this includes any assembler directives and comment lines The assembler does not like some characters like or in comments You ll find an 100 pages assembler manual in sdcc sdas doc asxhtm html or online at http sdcc svn sourceforge net viewvc checkout sdcc trunk sdcc sdas doc asxhtm html The compiler does not d
171. several approaches to debugging your code This chapter is meant to show your options and to give detail on some of them When writing your code write your code with debugging in mind avoid duplicating code put conceptually similar variables into structs use structured code have strategic points within your code where all variables are consistent run a syntax checking tool like splint see more pedantic 3 2 9 over the code for the high level code use a C compiler like f e GCC to compile run and debug the code on your host See see more pedantic 3 2 9 on how to handle syntax extensions like __xdata __at use another C compiler to compile code for your target Always an option but not recommended And not very likely to help you If you seriously consider walking this path you should at least occasionally check portability of your code Most commercial compiler vendors will offer an evaluation version so you can test compile your code or snippets of your code Debugging on a simulator there is a separate section about SDCDB section 5 1 below or 8051 specific use a free open source commercial simulator which interfaces to the AOMF file see 3 1 1 optionally generated by SDCC Debugging On target use a MCU port pin to serially output debug data to the RS232 port of your host You ll probably want some level shifting device typically involving a MAX232 or similar IC If the hardware serial port of the MC
172. sjmp nostdinc This will prevent the compiler from passing on the default include path to the preprocessor nostdlib This will prevent the compiler from passing on the default library path to the linker verbose Shows the various actions the compiler is performing V Shows the actual commands the compiler is executing no c code in asm Hides your ugly and inefficient c code from the asm file so you can always blame the compiler fverbose asm Include code generator and peep hole comments in the generated asm files no peep comments Don t include peep hole comments in the generated asm files even if fverbose asm option 1s specified i code in asm Include i codes in the asm file Sounds like noise but is most helpful for debugging the compiler itself less pedantic Disable some of the more pedantic warnings For more details see the less_pedantic pragma on page 56 disable warning lt nnnn gt Disable specific warning with number lt nnnn gt Werror Treat all warnings as errors print search dirs Display the directories in the compiler s search path VC Display errors and warnings using MSVC style so you can use SDCC with the visual studio IDE With SDCC both offering a GCC like the default and a MSVC like output style integration into most programming editors should be straightforward use stdout Send errors and warnings to stdout instead of stderr Wa asmOption asmOption Pass the asmOpti
173. sm _en dasm and _naked The compiler displays a warning keyword lt keyword gt is deprecated use __ lt key word gt instead in such cases The warning can be disabled by using pragma disable_warning 197 in the source file or disable warning 197 command line option Compliant equivalents of these keywords are always available in a form that begin with two underscores f e __data instead of data and __asm gt instead of _asm gt e Integer promotion of variable arguments is not performed if the argument is explicitly typecasted unless the std c89 or std c99 command line options are used void vararg_func char x str str void main void char c 10 x argument u is promoted to int before 100 8 3 CYCLOMATIC COMPLEXITY CHAPTER 8 SDCC TECHNICAL DATA x passing to function x vararg_func c Cc x argument u is not promoted to int x it is passed as char to function x if std cXX is not defined is promoted to int before passing x to function if std cXX is defined vararg_func Sbc char u 8 3 Cyclomatic Complexity Cyclomatic complexity of a function is defined as the number of independent paths the program can take during execution of the function This is an important number since it defines the number test cases you have to generate to validate the function The accepted industry standard for complexity number is 10
174. st be specified using the o option E Run only the C preprocessor Preprocess all the C source files specified and output the results to standard output 0 lt path file gt The output path where everything will be placed or the file name used for all generated output files If the parameter is a path it must have a trailing slash or backslash for the Windows bina ries to be recognized as a path Note for Windows users if the path contains spaces it should be surrounded by quotes The trailing backslash should be doubled in order to prevent escaping the fi nal quote for example o F Projects test3 output IN or put after the final quote for example o F Projects test3 output 1 The path using slashes for directory delimiters can be used too for example o F Projects test3 output 1 stack auto All functions in the source file will be compiled as reentrant 1 e the parameters and local variables will be allocated on the stack See section 3 7 Parameters and Local Variables for more details If this option is used all source files in the project should be compiled with this option It automatically implies int long reent and float reent callee saves function1 function2 function3 The compiler by default uses a caller saves convention for register saving across function calls however this can cause unnecessary register pushing and popping when calling small functions from larger functions This option
175. st software update mechanism patent issues is your project adequately positioned in that magic triangle fame fortune fun Maybe not all answers to these questions are known and some answers may even be no nevertheless knowing these questions may help you to avoid burnout Chances are you didn t want to hear some of them l burnout is bad for electronic devices programmers and motorcycle tyres 87 Chapter 7 Support SDCC has grown to be a large project The compiler alone without the preprocessor assembler and linker is well over 150 000 lines of code blank stripped The open source nature of this project is a key to its continued growth and support You gain the benefit and support of many active software developers and end users Is SDCC perfect No that s why we need your help The developers take pride in fixing reported bugs You can help by reporting the bugs and helping other SDCC users There are lots of ways to contribute and we encourage you to take part in making SDCC a great software package The SDCC project is hosted on the SDCC sourceforge site at http sourceforge net projects sdcc You ll find the complete set of mailing lists forums bug reporting system patch submission system wiki rss feed download area and Subversion code repository there 7 1 Reporting Bugs The recommended way of reporting bugs is using the infrastructure of the sourceforge site You can follow the status of bug re
176. stalls a signal handler to be able to delete temporary files after an user break AC or an exception If this environment variable is set SDCC won t install the signal handler in order to be able to debug SDCC TMP TEMP TMPDIR Path where temporary files will be created The order of the variables is the search order In a standard nix environment these variables are not set and there s no need to set them On Windows it s recommended to set one of them SDCC_HOME Path see section 2 2 Install Paths SDCC_INCLUDE Path see section 2 3 Search Paths SDCC_LIB Path see section 2 3 Search Paths There are some more environment variables recognized by SDCC but these are mainly used for debugging pur poses They can change or disappear very quickly and will never be documented 3 4 Storage Class Language Extensions 3 4 1 MCS51 DS390 Storage Class Language Extensions In addition to the ANSI storage classes SDCC allows the following MCS51 specific storage classes 3 4 1 1 data near This is the default storage class for the Small Memory model data and near or the more ANSI C compliant forms _ data and __near can be used synonymously Variables declared with this storage class will be allocated in the directly addressable portion of the internal RAM of a 8051 e g __ data unsigned char test_data Writing 0x01 to this variable generates the assembly code 75x00 01 mov _test_data 0x01 if you are cur
177. stant value Note that local variables and parameters are replaced by compiler generated temporaries Live ranges are computed only for temporaries i e live ranges are not computed for global variables Registers are allocated for temporaries only Operands are formatted in the following manner Operand Name Ir live from live to type information registers allocated As mentioned earlier the live ranges are computed in terms of the execution sequence number of the iCodes for example the iTemp0 is live from i e first defined in iCode with execution sequence number 3 and is last used in the Code with sequence number 5 For induction variables such as iTemp21 the live range computation extends the lifetime from the start to the end of the loop The register allocator used the live range information to allocate registers the same registers may be used for different temporaries if their live ranges do not overlap for example rO is allocated to both Temp6 and to iTemp17 since their live ranges do not overlap In addition the allocator also takes into consideration the type and usage of a temporary for example itemp6 is a pointer to near space and is used as to fetch data from i e used in GET_VALUE_AT_ADDRESS so it is allocated a pointer register r0 Some short lived temporaries are allocated to special registers which have meaning to the code generator e g iTemp13 is allocated to a pseudo register CC which tells the back end that
178. sting graphical user interfaces like ddd xxgdb or xemacs existing for the GNU debugger If you use a graphical user interface for the debugger you can skip this section break line file line function file function Set breakpoint at specified line or function sdcdb gt break 100 sdcdb gt break foo c 100 sdcdb gt break funcfoo sdcdb gt break foo c funcfoo clear line file line function file function Clear breakpoint at specified line or function sdcdb gt clear 100 sdcdb gt clear foo c 100 sdcdb gt clear funcfoo sdcdb gt clear foo c funcfoo continue Continue program being debugged after breakpoint finish Execute till the end of the current function delete n Delete breakpoint number n If used without any option clear ALL user defined break points 78 5 1 DEBUGGING WITH SDCDB CHAPTER 5 DEBUGGING info break stack frame registers e info break list all breakpoints e info stack show the function call stack e info frame show information about the current execution frame e info registers show content of all registers step Step program until it reaches a different source line Note pressing lt return gt repeats the last command next Step program proceeding through subroutine calls run Start debugged program ptype variable Print type information of the variable print variable print value of variable file filename load the given fil
179. t optimize labels makes the dumpfiles more readable no xinit opt Will not memcpy initialized data from code space into xdata space This saves a few bytes in code space if you don t have initialized data 29 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC nooverlay The compiler will not overlay parameters and local variables of any function see section Parameters and local variables for more details no peep Disable peep hole optimization with built in rules peep file lt filename gt This option can be used to use additional rules to be used by the peep hole optimizer See section 8 1 13 Peep Hole optimizations for details on how to write these rules peep asm Pass the inline assembler code through the peep hole optimizer This can cause unexpected changes to inline assembler code please go through the peephole optimizer rules defined in the source file tree lt target gt peeph def before using this option opt code speed The compiler will optimize code generation towards fast code possibly at the expense of code size opt code size The compiler will optimize code generation towards compact code possibly at the expense of code speed 3 2 9 Other Options vy version displays the sdcc version c compile only will compile and assemble the source but will not call the linkage editor clmode reads the preprocessed source from standard input and compiles it The file name for the assembler output mu
180. tack the new bank is selected and an indirect jump is made When the banked function returns it jumps to __sdcc_banked_ret which restores the previous bank and returns to the caller 4 1 3 2 Software When writing banked software using SDCC you need to use some special keywords and options You also need to take over a bit of work from the linker To create a function that can be called from another bank it requires the keyword banked The caller must see this in the prototype of the callee and the callee needs it for a proper return Called functions within the same bank as the caller do not need the banked keyword nor do functions in the common area Beware SDCC does not know or check if functions are in the same bank This is your responsibility Normally all functions you write end up in the segment CSEG If you want a function explicitly to reside in the common area put it in segment HOME This applies for instance to interrupt service routines as they should not be banked Functions that need to be in a switched bank must be put in a named segment The name can be mostly anything up to eight characters e g BANK1 To do this you either use codeseg BANK1 See 3 2 9 on the command line when compiling or pragma codeseg BANK1 See 3 19 at the top of the C source file The segment name always applies to the whole source file and generated object so functions for different banks need to be defined in different source files When linking you
181. tandard libraries STD_LIB STD_INT_LIB STD_LONG_LIB STD_FP_LIB STD_DS390_LIB STD_XA51_LIB and the environment variables SDCC_DIR_NAME SDCC_INCLUDE_NAME SDCC_LIB_NAME are defined by configure too At the moment it s not possible to change the default settings it was simply never required These configure options are compiled into the binaries and can only be changed by rerunning configure and recompiling SDCC The configure options are written in italics to distinguish them from run time environment variables see section search paths The settings for Win32 builds are used by the SDCC team to build the official Win32 binaries The SDCC team uses Mingw32 to build the official Windows binaries because it s 1 open source 2 a gcc compiler and last but not least 3 the binaries can be built by cross compiling on SDCC Distributed Compile Farm See the examples how to pass the Win32 settings to configure The other Win32 builds using VC or whatever don t use configure but a header file sdcc_vc_in h is the same as sdccconf h built by configure for Win32 These defaults are Variable default Win32 builds PREFIX usr local sdcc EXEC_PREFIX PREFIX PREFIX BINDIR EXEC_PREFIX bin SEXEC_PREFIX bin DATADIR DATAROOTDIR DATAROOTDIR DATAROOTDIR PREFIX share PREFIX DOCDIR SDATAROOTDIR sdcc doc DATAROOTDIR doc INCLUDE_DIR_SUFFIX sdec include include NON_FREE_INCLUD
182. tax checking like splint http www splint org To make your source files parseable by splint you will have to include lint h in your source file and add brackets around ex tended keywords like __ at Oxab and __ interrupt 2 Splint has an excellent on line manual at http www splint org manual and it s capabili ties go beyond pure syntax checking You ll need to tell splint the location of SDCC s include files so a typical command line could look like this splint I usr local share sdcc include mcs51 myprogram c short is 8bits Treat short as 8 bit for backward compatibility with older versions of compiler see section 1 4 use non free Search include non free licensed libraries and header files located under the non free directory see section 2 3 3 2 10 Intermediate Dump Options The following options are provided for the purpose of retargetting and debugging the compiler They provide a means to dump the intermediate code iCode generated by the compiler in human readable form at various stages of the compilation process More on Codes see chapter 9 1 The anatomy of the compiler dumpraw This option will cause the compiler to dump the intermediate code into a file of named lt source filename gt dumpraw just after the intermediate code has been generated for a function i e before any optimizations are done The basic blocks at this stage ordered in the depth first number so they may not be
183. te HL two bytes or DEHL four bytes The gbz80 port use the same set of registers for the return values but in a different order of significance E one byte DE two bytes or HLDE four bytes 4 4 The HCOS port The port to the Freescale Motorola HC08 family has been added in October 2003 and is still undergoing some basic development The code generator is complete but the register allocation is still quite unoptimized Some of the SDCC s standard C library functions have embedded non HC08 inline assembly and so are not yet usable The HC08 port passes the regression test suite see section 7 8 4 5 The PIC14 port The PIC14 port adds support for Microchip PIC MCUs with 14 bit wide instructions This port is not yet mature and still lacks many features However it can work for simple code Currently supported devices include 12F 629 635 675 683 16C 432 433 16C 554 557 558 16C 62 620 620a 621 621a 622 622a 63a 65b 16C 71 710 711 715 717 72 73b 745 74b 765 770 771 773 774 781 782 16C 925 926 16CR 620a 73 74 76 77 16F 616 627 627a 628 628a 630 636 639 648 648a 676 684 685 687 688 689 690 16F 716 72 73 737 74 747 76 767 77 777 785 16F 818 819 84 84a 87 870 871 872 873 873a 874 874a 876 876a 877 877a 88 886 887 16F 913 914 916 917 946 16HV 616 785 An up to date list of currently supported devices can be obtained via sdcc
184. terrupt functions using a particular bank it can be declared with the same using attribute as the calling interrupt functions For instance if you have several ISRs using bank one and all of them call memcpy it might make sense to create a specialized version of memcpy using 1 since this would prevent the ISR from having to save bank zero to the stack on entry and switch to bank zero before calling the function 43 3 12 STARTUP CODE CHAPTER 3 USING SDCC 3 12 Startup Code 3 12 1 MCS51 DS390 Startup Code The compiler triggers the linker to link certain initialization modules from the runtime library called crt lt something gt Only the necessary ones are linked for instance crtxstack asm GSINIT1 GSINITS is not linked unless the xstack option is used These modules are highly entangled by the use of special segments areas but a common layout is shown below main asm area HOME CODE __interrupt_vect ljmp __sdcc_gsinit_startup crtstart asm area GSINITO CODE sdcc_gsinit_startup mov sp __start__stack 1 crtxstack asm area GSINIT1 CODE sdec_ init xstack Need to initialize in GSINIT1 in case the user s __sdcc_external_startup uses the xstack mov __XPAGE __start__xstack gt gt 8 mov _spx __start__xstack crtstart asm area GSINIT2 CODE lcall __sdcc_external_startup mov a dpl jz __sdcc_init_data 13mp sdcc_program_startup sdeo init datas
185. the Medium Memory model e g __pdata unsigned char test_pdata Writing 0x01 to this variable generates the assembly code 78r00 mov r0 _test_pdata 74 01 mov a 0x01 F2 movx r0 a If the xstack option is used the pdata memory area is followed by the xstack memory area and the sum of their sizes is limited to 256 bytes 3 4 1 5 code Variables declared with this storage class will be placed in the code memory __ code unsigned char test_code Read access to this variable generates the assembly code 90s00r6F mov dptr _test_code E4 clr a 93 move a la dptr char indexed arrays of characters in code memory can be accessed efficiently __ code char test_array c h e a p Read access to this array using an 8 bit unsigned index generates the assembly code E5x00 mov a _index 90s00r41 mov dptr _test_array 93 move a la dptr 34 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 3 4 1 6 bit This is a data type and a storage class specifier When a variable is declared as a bit it is allocated into the bit addressable memory of 8051 e g _ bit test_bit Writing 1 to this variable generates the assembly code D2x00 s etb test_bit The bit addressable memory consists of 128 bits which are located from 0x20 to 0x2f in data memory Apart from this 8051 specific storage class most architectures support ANSI C bitfields In accordance with ISO IEC 9899 bits and bitfie
186. ts Microcontroller conductor Support_Tools asp Ramtron Goal Semi Installing and Configuring SDCC and http www ramtron com doc Products Microcontroller conductor Crimson Editor Support_Tools asp Texas Instruments MSC12xx Programming with SDCC http focus ti com general docs lit getliterature tsp literatureNumber sbaal09 amp fileType pdf 6 8 Some Questions Some questions answered some pointers given it might be time to in turn ask you some questions can you solve your project with the selected microcontroller Would you find out early or rather late that your target is too small slow whatever Can you switch to a slightly better device if it doesn t fit should you solve the problem with an 8 bit CPU Or would a 16 32 bit CPU and or another programming language be more adequate Would an operating system on the target device help if you solved the problem will the marketing department be happy if the marketing department is happy will customers be happy if you re the project manager marketing department and maybe even the customer in one person have you tried to see the project from the outside is the project done if you think it is done Or is just that other interface protocol feature configuration option missing How about website manual s internationali zls ation packaging labels 2nd source for compo nents electromagnetic compatability interference documentation for production production te
187. u sdk arch i386 arch ppc CXXFLAGS 02 isysroot Developer SDKs MacOSX10 4u sdk arch 1386 arch ppc CFLAGS 02 isysroot Developer SDKs MacOSX10 4u sdk arch i386 arch ppc 2 4 3 Cross compiling SDCC on Linux for Windows With the Mingw32 gcc cross compiler it s easy to compile SDCC for Win32 See section Configure Options 2 4 4 Building SDCC using Cygwin and Mingw32 For building and installing a Cygwin executable follow the instructions for Linux On Cygwin a native Win32 binary can be built which will not need the Cygwin DLL For the necessary configure options see section configure options or the script sdcc support scripts sdec_cygwin_mingw32 In order to install Cygwin on Windows download setup exe from www cygwin com http www cygwin com Run it set the default text file type to unix and download install at least the following packages Some packages are selected by default others will be automatically selected because of dependencies with the manually selected packages Never deselect these packages e flex e bison e gcc version 3 x is fine no need to use the old 2 9x binutils selected with gcc e make e rxvt a nice console which makes life much easier under windoze see below e man not really needed for building SDCC but you ll miss it sooner or later e less not really needed for building SDCC but you ll miss it sooner or later e svn only if you use S
188. ubversion access If you want to develop something you ll need e python for the regression tests e gdb the gnu debugger together with the nice GUI insight e openssh to access the CF or commit changes e autoconf and autoconf devel if you want to fight with configure don t use autoconf stable rxvt is a nice console with history Replace in your cygwin bat the line 15 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC bash login i with one line rxvt sl 1000 fn Lucida Console 12 sr cr red bg black fg white geometry 100x65 e bash login Text selected with the mouse is automatically copied to the clipboard pasting works with shift insert The other good tip is to make sure you have no c style paths anywhere use cygdrive c instead Using invokes a network lookup which is very slow If you think cygdrive is too long you can change it with e g mount s u c mnt SDCC sources use the unix line ending LF Life is much easier if you store the source tree on a drive which is mounted in binary mode And use an editor which can handle LF only line endings Make sure not to commit files with windows line endings The tabulator spacing used in the project is 8 Although a tabulator spacing of 8 is a sensible choice for programmers it s a power of 2 and allows to display 8 16 bit signed variables without loosing columns the plan is to move towards using only spaces in the source 2 4 5 Bui
189. uence or not too many case labels are missing switch i switch 1 case 4 case 0 case 5 Case 1 case 3 Case 6 case 3 case 7 case 4 case 8 case 5 case 9 case 6 93 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA Case 10 Sto Case 7 Case 11 Ls Case 8 Both the above switch statements will be implemented using a jump table The example to the right side is slightly more efficient as the check for the lower boundary of the jump table is not needed e The number of case labels is not larger than supported by the target architecture e If the case labels are not in numerical sequence gaps between cases SDCC checks whether a jump table with additionally inserted dummy cases is still attractive e If the starting number is not zero and a check for the lower boundary of the jump table can thus be eliminated SDCC might insert dummy cases 0 Switch statements which have large gaps in the numeric sequence or those that have too many case labels can be split into more than one switch statement for efficient code generation e g switch i case 1 case 2 case 3 case 4 case 5 case 6 case 7 case 101 case 102 case 103 case 104 case 105 case 106 case 107 If the above switch statement is broken down into two switch statements switch case case case case case case case H pe JO OB WNP NH and switch i case 101 case 102 case 103 case 104 cas
190. upts nojtbound will not generate code for boundary value checking when switch statements are turned into jump tables dangerous For more details see section 8 1 7 noloopreverse Will not do loop reversal optimization nooverlay the compiler will not overlay the parameters and local variables of a function stackauto See option stack auto and section 3 7 Parameters and Local Variables opt_code_speed The compiler will optimize code generation towards fast code possibly at the expense of code size Currently this has little effect 56 3 19 PRAGMAS CHAPTER 3 USING SDCC opt_code_size The compiler will optimize code generation towards compact code possibly at the expense of code speed Currently this has little effect opt_code_balanced The compiler will attempt to generate code that is both compact and fast as long as meeting one goal is not a detriment to the other this is the default std_sdcc89 Generally follow the C89 standard but allow SDCC features that conflict with the standard default std_c89 Follow the C89 standard and disable SDCC features that conflict with the standard std_sdcc99 Generally follow the C99 standard but allow SDCC features that conflict with the standard incomplete support std_c99 Follow the C99 standard and disable SDCC features that conflict with the standard incomplete support codeseg lt name gt Use this name max 8 characters for the code segment Se
191. urn value 59 Furthermore warnings of less importance of PEDANTIC and INFO warning level are disabled too namely constant value out of range 81 left right shifting more than size of object changed to zero 116 unreachable code 126 integer overflow in expression 165 unmatched pragma save and pragma restore 170 comparison of signed char with unsigned char requires promotion to int 185 ISO C90 does not support flexible array members 187 extended stack by number bytes for compiler temp s in function function name 114 function function name edges number nodes number cyclomatic complexity number 121 disable_warning lt nnnn gt the compiler will not warn you anymore about warning number lt nnnn gt nogcse will stop global common subexpression elimination noinduction will stop loop induction optimizations noinvariant will not do loop invariant optimizations For more details see Loop Invariants in section8 1 4 noiv Do not generate interrupt vector table entries for all ISR functions defined after the pragma This is useful in cases where the interrupt vector table must be defined manually or when there is a secondary manually defined interrupt vector table e g for the autovector feature of the Cypress EZ USB FX2 More elegantly this can be achieved by omitting the optional interrupt number after the interrupt keyword see section 3 9 about interr
192. used to compile the program the parameters and local variables of all reentrant functions are allocated in this area This option is provided for programs with large stack space requirements When used with the stack auto option all parameters and local variables are allocated on the external stack note support libraries will need to be recompiled with the same options There is a predefined target in the library makefile The compiler outputs the higher order address byte of the external ram segment into port P2 see also section 4 1 therefore when using the External Stack option this port may not be used by the application program 3 18 2 DS390 Memory Model The only model supported is Flat 24 This generates code for the 24 bit contiguous addressing mode of the Dallas DS80C390 part In this mode up to four meg of external RAM or code space can be directly addressed See the data sheets at www dalsemi com for further information on this part Note that the compiler does not generate any code to place the processor into 24 bitmode although tinibios in the ds390 libraries will do that for you If you don t use tinibios the boot loader or similar code must ensure that the processor is in 24 bit contiguous addressing mode before calling the SDCC startup code Like the model large option variables will by default be placed into the XDATA segment Segments may be placed anywhere in the 4 meg address space using the usual loc options
193. usr local share not on Win32 non free sdcc non free include INCLUDE_DIR_SUFFIX 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC The option nostdinc disables all search paths except 1 and 2 3 Library files With the exception of L dir the model is auto appended by the compiler e g small large z80 ds390 etc Search path default Win32 builds 1 L dir L dir L dir 2 SDCC_LIB lt model gt SDCC_LIB lt model gt SDCC_LIB lt model gt 3 SDCC_HOME SDCC_HOME SDCC_HOME S PREFIX2DATA_DIR share sdcc lib lt model gt lib lt model gt LIB_DIR_SUFFIX lt model gt 4 path argv 0 path argv 0 sdcc path argv 0 BIN2DATADIR lib lt model gt MUDA LIB_DIR_SUFFIX lt model gt lt model gt 5 DATADIR non free usr local share sdcc not on Win32 LIB_DIR_SUFFIX lib lt model gt lt model gt 6 SDCC_HOME SDCC_HOME share sdcc SDCC_HOME PREFIX2DATA_DIR non free lib lt model gt lib non free lt model gt non free LIB_DIR_SUF FIX lt model gt 7 path argv 0 path argv 0 sdcc path argv 0 BIN2DATADIR non free lib lt model gt lib non free lt model gt non free LIB_DIR_SUFFIX lt model gt 8 DATADIR Mon free usr local share sdcc not on Win32 LIB_DIR_SUFFIX non free lib lt model gt lt model gt The option nostdlib disables all search paths except 1 and 2 2 4 Building
194. ust not include the adc i2c and usart sources in the Makefile am in step 9 70 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS Pointer sizes according to memory model small model large model code pointers 16 bits 24 bits data pointers 16 bits 16 bits It is advisable that all sources within a project are compiled with the same memory model If one wants to override the default memory model this can be done by declaring a pointer as far or near Far selects large memory model s pointers while near selects small memory model s pointers The standard device libraries see 4 6 8 contain no reference to pointers so they can be used with both memory models 4 6 12 Stack The stack implementation for the PIC16 port uses two indirect registers FSR1 and FSR2 FSR1 is assigned as stack pointer FSR2 is assigned as frame pointer The following stack models are supported by the PIC16 port e SMALL model e LARGE model SMALL model means that only the FSRxL byte is used to access stack and frame while LARGE uses both FSRxL and FSRxH registers The following table shows the stack frame pointers sizes according to stack model and the maximum space they can address Stack amp Frame pointer sizes according to stack model small large Stack pointer FSR1 8 bits 16 bits Frame pointer FSR2 8 bits 16 bits LARGE stack model is currently not working proper
195. variable PATH to include the location of the bin directory or start sdcc using the full path Windows Install Using the Setup Program Download the setup program sdcc x y z setup exe for an official release from http shots sf net project showfiles php group_id 599 or a setup program for one of the snap sdcc yyyymmdd xxxx setup exe from http sdcc sf net snap php and execute it A windows typical installer will guide you through the installation process 2 4 8 VPATH feature SDCC supports the VPATH feature provided by configure and make It allows to separate the source and build trees Here s an example cd cd SHOME tar xjf sdcc src yyyymmdd rrrr tar bz2 extract source to directory sdcc mkdir sdcc build put output in sdcc build cd sdcc build sdcc configure configure is doing all the magic make That s it configure will create the directory tree will all the necessary Makefiles in sdcc build It automagically computes the variables srcdir top_srcdir and top_buildir for each directory After running make the generated files 17 2 5 BUILDING THE DOCUMENTATION CHAPTER 2 INSTALLING SDCC will be in sdcc build while the source files stay in sdcc This is not only usefull for building different binaries e g when cross compiling It also gives you a much better overview in the source tree when all the generated files are not scattered between the source files And the best thing is
196. verlap any other memory areas such as used register banks or the data segment and with enough space for the current application The pack iram option which is now a default setting will override this setting so you should also specify the no pack iram option if you need to manually place the stack xstack loc lt Value gt By default the external stack is placed after the pdata segment Using this option the xstack can be placed anywhere in the external memory space of the 8051 The value entered can be in Hexadecimal or Decimal format e g xstack loc 0x8000 or stack loc 32768 The provided value should not overlap any other memory areas such as the pdata or xdata segment and with enough space for the current application data loc lt Value gt The start location of the internal ram data segment The value entered can be in Hexadecimal or Decimal format eg data loc 0x20 or data loc 32 By default the start location of the internal ram data segment is set as low as possible in memory taking into account the used register banks and the bit segment at address 0x20 For example if register banks 0 and 1 are used without bit variables the data segment will be set if data loc is not used to location 0x10 idata loc lt Value gt The start location of the indirectly addressable internal ram of the 8051 default value is 0x80 The value entered can be in Hexadecimal or Decimal format eg idata loc 0x88 or idata loc 136
197. vfprintf FILE fp char xfmt va_list ap For sprintf and vsprintf buf should normally be a data pointer where the resulting string will be placed No range checking is done so the user should allocate the necessary buffer For fprintf and vfprintf fp should be a stream pointer i e stdout STREAM_MSSP etc 4 6 17 3 Signals The PIC18F family of microcontrollers supports a number of interrupt sources A list of these interrupts is shown in the following table signal name description signal name description SIG_RB PORTB change interrupt SIG_EE EEPROM FLASH write complete interrupt SIG_INTO INTO external interrupt SIG_BCOL Bus collision interrupt SIG_INT1 INT1 external interrupt SIG_LVD Low voltage detect interrupt SIG_INT2 INT2 external interrupt SIG_PSP Parallel slave port interrupt SIG_CCP1 CCP1 module interrupt SIG_AD AD convertion complete interrupt SIG_CCP2 CCP2 module interrupt SIG_RC USART receive interrupt SIG_TMRO TMRO overflow interrupt SIG_TX USART transmit interrupt SIG_TMR1 TMR1 overflow interrupt SIG_MSSP SSP receive transmit interrupt SIG_TMR2 TMR2 matches PR2 interrupt SIG_TMR3 TMR3 overflow interrupt The prototypes for these names are defined in the header file signal h In order to simplify signal handling a number of macros is provided DEF_INTHIGH name begin the definition of the interrupt dispatch table for high priority interrupts name is the function
198. y valid integer will do Please refer to the assemblers documentation for further details 8Here the C label cl abe is translated by the compiler into a local label so the locality of labels within the function is not broken 49 3 14 INTERFACING WITH ASSEMBLER CODE CHAPTER 3 USING SDCC 3 14 Interfacing with Assembler Code 3 14 1 Global Registers used for Parameter Passing The compiler always uses the global registers DPL DPH B and ACC to pass the first non bit parameter to a function and also to pass the return value of function according to the following scheme one byte return value in DPL two byte value in DPL LSB and DPH MSB three byte values generic pointers in DPH DPL and B and four byte values in DPH DPL B and ACC Generic pointers contain type of accessed memory in B 0x00 xdata far 0x40 idata near 0x60 pdata 0x80 code The second parameter onwards is either allocated on the stack for reentrant routines or if stack auto is used or in data xdata memory depending on the memory model Bit parameters are passed in a virtual register called bits in bit addressable space for reentrant functions or allocated directly in bit memory otherwise Functions with two or more parameters or bit parameters that are called through function pointers must there for be reentrant so the compiler knows how to pass the parameters 3 14 2 Registers usage Unless the called function is declared as
199. ype promotion 8 41 46 47 82 Typographic conventions 7 uCsim 84 union 99 UnxUtils 16 USE_FLOATS 53 using mcs51 ds390 register bank 36 40 41 43 using mcs51 ds390 register bank 36 40 41 43 vararg va_arg 7 83 Variable initialization 29 38 46 version 18 89 version macro 59 volatile 38 40 43 48 83 VPATH 17 Warnings 31 warranty 7 watchdog 46 83 wiki 85 89 102 XA51 26 xdata hc08 storage class 37 __xdata hc08 storage class 37 xdata mcs51 ds390 storage class 27 34 36 38 46 __xdata mcs51 ds390 storage class 34 36 XEmacs 80 _XPAGE mcs531 60 xstack 27 Z180 37 T O memory 37 Options portmode 37 Pragmas pragma portmode 37 Z80 26 29 37 42 46 61 T O memory 37 116 interrupt 42 Options asm lt Value gt 29 callee saves bc 29 codeseg lt Value gt 29 constseg lt Value gt 29 no std crt0 29 portmode lt Value gt 29 return value 62 stack 61 Storage class 37 z80 59

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