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SDCC Compiler User Guide

1. 41 3 13 2 Assembler Routine non reentrant 2 41 3 13 3 Assembler Routine reentrant o s ses a co eoa e ea ek a we JERCA 42 int 16 bit and long 32 bit Suppott 43 Floating Point Support oe sso lt e raoe stopa a Be ls ee be wd a Ga a 43 CONTENTS CONTENTS 316 Library RONDES cia a e eR A eG Bee aA a EL eS OR 44 3 16 1 Compiler support routines gptrget mulintete 44 3 16 2 Stdclib functions puts printf streatetc 44 S120 SiGe oe Le we Re a ee ee ae eS 44 3 16 3 Math functions sin pow sqrt etc coco eR EE a 44 Soe Cer DANES se ka ee See Oe poe gi em VE eee ee OR podeli ee 4 44 217 Menure Modelado ed hee Se ed ee id ea T 44 Sli MUSSI Memory Models s croes we GA Ae ee RS Sew s 4 eae 44 JAILLI Small Medium and Large ooo we a we ES ae wee a 44 JIFLI Exiemel Stee eg ba ok eR ee ee AR 44 3 17 2 DS390 Memory Model gt gt o e ies ee EE EH RE Ee Oe EES 45 SA OWNS E Seo a Seg el ee AE Beda Bh ee ow ik Eb ae 45 3 19 Defines Created by The Compiler 26 2 oe eR Re EE EW Re ee ee eee aS 47 4 Notes on supported Processors 48 AT MESSI yaan e bd y SAAS ERS REYES LESSEE EES SE 2S GS 48 4 11 POSE access by SER o ke Se ee AE Re el SA ee ee N 48 41 2 Other Features available by SFR ooo 2684 6 Se ee ye PADS RES Ye EEN a 6 48 Bo DSU HOM e bee pa da ree dee bas Ge a A eb a web aces delih oe Bs 48 4 3 The 280 and eb280 pot e cec A
2. PRJ hex OBJS mplink v PRJ lkr m PRJ map o PRJ hex OBJS libsdcc lib 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 list see sdec help debug extra emit debug info in assembly output no pcode opt disable slightly faulty optimization on pCode 4 5 6 The library 4 5 6 1 error missing definition for symbol __gptrgetl 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 to the linker s arguments Make sure you also add an include path for the library using the I switch to the linker 4 5 6 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 unneccesary BANKSELs migth be removed 4 5 7 Know
3. 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 reversible 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 lt lt lt expression gt lt sym gt lt sym gt 1 lt for body 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 i j 0 changed to i j i 2 changed to i gt gt 1 i j j changed to i 0 i j 1 changed to i j Note the subexpressions given above are generally introduced by macro expansions or as a result of copy co
4. Higher Order Word 76 Highest Order Bit 75 HTML version of this document 15 VO memory Z80 Z180 31 iCode 27 81 82 idata mcs51 ds390 storage class 23 28 31 indent source formatting tool 67 Install paths 10 Install trouble shooting 16 Installation 8 int 16 bit 43 int 64 bit not supported 79 Intel hex format 19 23 61 Intermediate dump options 27 interrupt 31 34 36 37 40 43 45 46 49 interrupt jitter 36 interrupt latency 36 interrupt mask 36 interrupt priority 36 37 interrupts 37 jump tables 72 K amp R style 79 Labels 41 Libraries 20 22 26 30 44 Linker 20 Linker documentation 66 Linker options 22 lint syntax checking tool 27 little endian 75 Live range analysis 27 80 82 local variables 33 34 44 66 lock 37 long 32 bit 43 long long not supported 79 longjmp not supported 79 Loop optimization 27 71 83 Loop reversing 24 72 Mailing list s 68 69 main return 26 MCSS1 21 MCS51 memory 30 MCS51 memory model 44 MGCS51 options 23 INDEX INDEX MCSS51 variants 48 77 Memory map 19 Memory model 30 34 44 45 Microchip 50 Modulus 35 Motorola S19 format 19 23 Multiplication 34 35 72 83 Naked functions 39 near storage class 28 Nibble swapping 75 objdump tool 19 67 Object file 19 Optimization options 24 Optimizations 70 81 Options assembler 26 Options DS390 24 Options in
5. Parameters and local variables of functions that contain 16 or 32 bit multiplication or division will NOT be overlayed since these are implemented using external functions e g 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 overlayed 3 8 Interrupt Service Routines 3 8 1 General Information SDCC allows interrupt 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 using keyword can be used to tell the compiler to use the specified register bank 8051 specific when generating code
6. 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 no peep comments Will not include peep hole comments in the generated files 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 jwk burps please be more specific here please disable warning lt nnnn gt Disable specific warning with number lt nnnn gt 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 visual studio use stdout Send errors and warnings to stdout instead of stderr Wa asmOption asmOption Pass the asmOption to the assembler See file sdcc as doc asxhtm html for as sembler options cd 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 Thi
7. mds390 Generate code for the Dallas DS80C390 processor mds400 Generate code for the Dallas DS80C400 processor mhc08 Generate code for the Freescale Motorola HC08 family of processors mz80 Generate code for the Zilog Z80 family of processors mgbz80 Generate code for the GameBoy Z80 processor Not actively maintained 21 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC mavr Generate code for the Atmel AVR processor In development not complete AVR users should probably have a look at winavr http sourceforge net projects winavr or http www avrfreaks net index php name PNphpBB2 file index 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 3 2 2 Preprocessor Options I lt path gt The additional location where the pre processor 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 f
8. unsigned char hobl aobl bit hob2 hobl hob2 hob3 aobl hob3 aob2 aob3 gint gt gt 15 1 gint gt gt 15 1 gint amp 0x8000 gint gt gt 9 1 aob2 gint gt gt 8 1 aob3 gint amp 0x0800 will generate the following code 00 00 00 00 001 001 001 001 001 001 001 001 001 OA OC 0D OF D E E5 01 23 54 01 F5 02 E5 01 33 92 00 E5 01 33 92 01 E5 01 03 54 01 61 62 63 64 65 66 67 68 69 66 67 68 69 70 71 72 73 hob c 7 mov rl anl mov hob c 8 mov rle mov hob c 9 mov rlc mov hob c 10 mov rr anl a gint 1 a a 0x01 foo hobl 1 1 a gint 1 foo hob2 1 1 a gint 1 a foo hob3 1 1 a gint 1 a a 0x01 C re 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 75 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA 0020 F5 03 74 mov foo aobl 1 1 a 15 bobne 11 0022 E5 01 76 mov a _gint 1 0024 13 17 rrc 0025 92 02 78 mov _foo_aob2_1_1 c 79 hob c 12 0027 E5 01 80 mov a _gint 1 0029 A2 E3 81 mov c acc 3 002B 92 03 82 mov _foo_aob3_1_1 c Other variations of these cases however will not be recognized They are standard C expressions so I heartil
9. 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 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 sdec index html 4 3 The Z80 and gbz80 port SDCC can target both the Zilog and the Nintendo Gameboy s Z80 like gbz80 The Z80 port is passed through the same regressions tests 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 registers and BC and DE are available for holding variables Return values for the Z80 port are stored in L one byte 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 48 4 4 THE HC08 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 4 The HC08 por
10. 66 67 sdcpp preprocessor 17 22 Search path 10 semaphore 37 setjmp not supported 79 sfr 30 31 48 sfr16 30 sfr32 30 signal handler 27 sloc spill location 24 splint syntax checking tool 27 67 srecord bin hex tool 19 23 67 stack 23 25 28 31 33 35 36 44 48 71 stack overflow 35 Startup code 37 static 33 Status of documentation 6 15 Storage class 28 31 34 44 Strength reduction 71 83 Subexpression 72 Subexpression elimination 24 70 Support 68 swapping nibbles bytes 75 switch statement 24 72 74 Symbol listing 19 tabulator spacing 8 columns 13 Test suite 69 Tinibios DS390 45 INDEX INDEX TLCS 900H 22 TMP TEMP TMPDIR 27 Tools 66 Trademarks 86 type conversion 6 type promotion 6 65 Typographic conventions 6 UnxUtils 13 USE_FLOATS 44 using mcs51 ds390 register bank 31 34 35 37 Variable initialization 24 32 37 version 15 69 volatile 32 34 37 40 Warnings 26 warranty 6 XASI 22 xdata hc08 storage class 32 xdata mcs51 ds390 storage class 22 28 31 32 37 XEmacs 64 Z180 31 Z80 21 31 48 Z80 options 24 91
11. DATA pi ds 2 _gint ds 2 sample c 5 gt function function _function Tempo lr3 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 lr7 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 83 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS inc rO mov ar3 r0 dec r0 mov a r2 orl a r3 jz 00103 00114 iITemp7 lr9 13 4 far int DPTR _p lr0 0 4 far int mov dpl p mov dph _p 1 5 _p lr0 0 _far int p Ir0 0 _far int 0x2 short mov a 0x02 add a _p mov _p a clra addc a _p 1 mov _p 1 a iTemp10 Ir13 14 int r2 r3 iTemp7 lr9 13 far int DPTR movx a dptr mov r2 a inc dptr movx a dptr mov r3 a GTemp6 Ir5 16 _near int r0 lt iTemp10 Ir13 14 int r2 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 40x00 Temp21 lr21 38 short r4 0x0 short mov r4 40x00 iTemp23 1r22 38 int r5 r6 Oxa int mov r5 0x0A mov r6 40x00 iTemp17 lr23 3
12. If you re short on memory you might want to use printf small instead of printf For the mcs51 there additionally are assembly versions printf_tiny and printf fast and printf fast f 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 3 16 3 Math functions sin pow sqrt etc 3 16 4 Other 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 Ec 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 3 17 Memory Models 3 17 1 MCS51 Memory Models 3 17 1 1 Small Medium and Large SDCC allows three memory models for MCS51 code small medium and large Modules compiled with different memory models should never be combined together or the resul
13. for this function Interrupt service routines open the door for some very interesting bugs If an interrupt service routine changes variables which are accessed by other functions these variables have to be declared volatile 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 34 3 8 INTERRUPT SERVICE ROUTINES CHAPTER 3 USING SDCC 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 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 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
14. 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 Tf you should know why please drop us a note 2 8 INSTALL TROUBLE SHOOTING CHAPTER 2 INSTALLING SDCC 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 strl testing Compile this by typing sdec test c This should generate a test ihx output file and it should give no warnings such as not finding the 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
15. 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 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 75 00 01 mov _test_data 0x01 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 78x00 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 28 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 3 4 1 4 pdata Paged xdata access is just as straightforward as using the other
16. Temp23 Ir22 38 int 15 r6 Oxa int Sample c 15 23 58 0 iTemp17 Ir23 38 int 17 r0 Oxle int Sample c 15 24 26 1 _forcond_0 4 Sample c 15 25 27 1 Temp13 Ir25 26 char CC iTemp21 lr21 38 short r4 lt Oxa short Sample c 15 26 28 1 if iTemp13 lr25 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 Ir21 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 rl Sample c 18 32 36 1 1 iTemp17 lr23 38 int r7 r0 lt iTemp17 lr23 38 int r7 r0 0x3 short Sample c 18 33 37 1 _gint Ir0 0 int _gint 1r0 0 int iTemp17 lr23 38 int r7 r0 Sample c 15 36 42 1 iTemp21 Ir21 38 short r4 Temp21 Ir21 38 short r4 0x1 short Sample c 15 37 45 1 iTemp23 Ir22 38 int r5 r6 lt 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 iTemp24 1r40 41 4short DPTR iTemp2 Ir18 40 short r2 ITempl1 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
17. _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 don t have to call these routines directly The compiler will use them automatically every time an integer operation is required 3 15 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 f
18. 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 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 atdptr 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 E5 00 mov a _index 90s00r41 mov dptr 4 test array 93 move a latdptr 3 4 1 6 bit This is a data type and a storage class specifier When a variable is declared as a bit 1t is allocated into the bit addressable memory of 8051 e g bit test_bit Writing 1
19. 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 BBI here we are not sure if BB2 or BB3 was executed but we are SURE that BB1 was executed 85 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 tribution sets etc You know who you are 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 86 Index Aquestion answer 22 C 22 D lt macro value gt 22 E 22 25 I lt path gt 22 L lib path 22 M 22 MM 22 S 25 Umacro 22 V 26 Wa asmOption asmOption 26 WI linkOption linkOption 23 Wp preprocessorOption preprocessorOption 22 clmode 25 callee saves 25 callee saves bc 24 code loc lt Value
20. are Keyword Description Module to link ignore ignore all library pragmas none c link the C library libc18flib math link the Math libarary libm18f 11b io link the I O library libio18f 11b debug link the debug library libdebug lib is the device number i e 452 for PIC18F452 MCU This feature allows for linking with specific libraries withoug having to explicit name them in the command line Note that the IGNORE keyword will reject all modules specified by the library pragma The old format ie pragma stack Ox5ff is 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 53 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS udata 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 pragma udata bank2 foo char foo In order for this pragma to work extra SECTION directives should be added in the Ikr script In the following example a sample Ikr file is shown Sample linker script for the PIC18F452 processor LIBPATH CODEPAGE AME vectors START 0x0 END 0x29 PROTECTED CODEPAGE AME page START 0x2A END 0x7FFF CODEPAGE AME idlocs START 0x2000
21. 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 HC08 and Zilog Z80 based MCUs It can be retargetted for other microprocessors support for Microchip PIC Atmel AVR is under development The entire source code for the compiler is distributed under GPL SDCC uses ASXXXX amp ASLINK an open source retargettable 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 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 e char 8 bits 1 byte e short and int 16 bits 2 bytes e long 32 bit 4 bytes e float 4 byte IEEE The compiler also allows inline assembler code to be embedded anywhere in a function In addition routines developed in assembly can also be call
22. currently doesn t build under Borland C 2 If you modify any source files and need to rebuild be aware that the dependencies may not be correctly calculated The safest option is to delete all obj files and run the build again From a Cygwin BASH prompt this can easily be done with the command be sure you are in the sdcc directory find Y name obj o name lib o name rul Y print exec rm or on Windows NT 2000 XP from the command prompt with the command del s obj lib rul from the sdcc directory 2 4 8 Windows Install Using a ZIP Package 1 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 direc tory structure after unpacking the mingw32 package is c sdcc bin for the executables c sdcc include and cisdecMib for the include and libraries 2 Adjust your environment variable PATH to include the location of the bin directory or start sdcc using the full path 2 4 9 Windows Install Using the Setup Program Download the setup program sdcc x y z setup exe for an official release from http sf net project showfiles php group_id 599 or a setup program for one of the snapshots sdcc_yyyymmdd_setup exe from http sdcc sf net snap php and execute it A windows typical installer will guide you through the installation process 2 5 BUILDING THE DOCUMENTATI
23. directly by anonymous CVS on cvs sdcc sourceforge net 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 mcs5l 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 or section 2 4 9 More detailled 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 docdir environment variable see table below include_dir_suffix environment variable see table below lib_dir_suffix environment variable see table below sdceconf h dir separator environment variable either or makes sense here This character will only be used in sdceconf h don t forget it s a C header therefore a double backslash is needed there disable mcs51 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 disable ds390 port Excludes the DS390 port disable hc08 port Excludes the HC08 port disable pic port Excludes the PIC port disable xa51 port Exc
24. ee se A RO E a RE RAE ee ig Ree 32 Parameters amp Local Vartables 2 05 ced bee Dobe eRe Re HESS BARE ERS A 33 CINTIA NINE acuosas AED REPRE ERD RE AR ERE ES A 34 Interrupt Service Routines o ocs oo ee eta bea a ek Ee oe si 34 3 8 1 General InfOnmation cos osas ea eR a lk eh 34 3 8 2 MCS51 DS390 Interrupt Service Routines 35 3 8 3 HCOS Interrupt Service Routes 2 4 05 0064 85445 a a e 35 3 8 4 Z80 Interrupt Service Routines gt lt eso c s o ss eses ee 35 Enabling and Disabling Interrupts s lt cco ee bebe ew ed e 36 39 1 Critical Functions and t ritical Statements o lt voe g eR Re ee a ee 36 3 9 2 Enabling and Disabling Interruptsdirectly 36 39 3 Semaphore locking mesas ss scr ds Ge Gob eee a 37 Functions using private register banks mcs51 ds390 37 SiP COIE A SA eS eS Sy GS eS BGR SE Ble Y 37 3 11 1 MUSSIDS3OO Startup Cod oe o e eese eou ee he ee 37 211 2 HOOS SANIP Colo ja a AA Ea a a Bk EEA 38 311 3 LAO STAN Code oea e eA wee o Bh A eed 38 Inline Assembler Code so cca eke SLA RR EE ee Gy Je aw ik kopel 8 38 3 121 A Step by Step niaduchon cece s esea e Re a ee 38 Sle Naked FU DONE ei eas amp eae ees eee Be PR EEOC e Bees 39 3 123 Use of Labels within Inline Assembler ce ee ee ee ee GO ee 40 Interfacing with Assembler Code cs ee ewe ee LAN ee eee ewe N 41 3 13 1 Global Registers used for Parameter Passing
25. i j int main return c_func 10 9 The corresponding assembler routine is globl _asm_func _asm_func push _bp ov _bp sp ov r2 dpl ov a _bp add a 0xfd ov r0 a add a 0xfc ov rl a ov a r0 add a r2 ov dpl a ov dph 0x00 ov sp _bp pop _bp ret The compiling and linking procedure remains the same however note the extra entry amp exit linkage required for the assembler code _bp is the stack frame pointer and is used to compute the offset into the stack for parameters and local variables 42 3 14 INT 16 BIT AND LONG 32 BIT SUPPORT CHAPTER 3 USING SDCC 3 14 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
26. implementation Therefore SDCC ignores the optional interrupt number and does not attempt to generate an interrupt vector table 35 3 9 ENABLING AND DISABLING INTERRUPTS CHAPTER 3 USING SDCC By default SDCC generates code for a maskable interrupt which uses an RETI instruction to return from the interrupt To write an interrupt handler for the non maskable interrupt which needs an RETN instruction instead add the critical keyword void nmi_isr void critical interrupt 3 9 Enabling and Disabling Interrupts 3 9 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 critical i More than one statement could have been included in the block 3 9 2 Enabling and Disabling Interrupts directly Interrupts can also be disabled and enabled directly 8051 EA 0 or EA_SAVE EA EA 0 EA 1 EA EA_SAVE On other architectures which have seperate opcodes for enabling and disabling interrupts you might want to make
27. 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 8 4 What the make install command does This will install the compiler other executables libraries and include files into the appropriate 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 16 2 9 COMPONENTS OF SDCC CHAPTER 2 INSTALLING SDCC As SDCC grows to include support for other processors other packag
28. not guaranteed 3 4 1 8 Pointers to MCS51 DS390 specific memory spaces SDCC 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 in internal ram pointing to object in external ram pointer physically i data p xdata unsigned char pointer physically in external ram pointing to object in internal ram data unsigned char xdata p n code rom pointing to data in xdata space pointer physically i code p xdata unsigned char pointer physically in code space pointing to data in code space code unsigned char code p the following is a generic pointer physically located in xdata space char xdata p 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 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 memo
29. saving across function calls however this can cause unnecessary register pushing amp popping when calling small functions from larger functions This option 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 amp exit function prologue amp epilogue for these functions to save amp restore the registers used by these functions this can SUBSTANTIALLY reduce code amp 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 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 no
30. segments gt 64k 3 18 Pragmas SDCC supports the following pragma directives e save this will save all current options to the save restore stack See pragma restore e 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 e 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 amp 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 save registers when calling these functions extra code need to be manually inserted at the entry amp exit for these functions to save amp restore the registers used by these functions this can SUBSTANTIALLY reduce code amp 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 the function names specified in pragma callee_saves is appended to the list of functions specified in the command line e exclude none acc b dpl dph The exclude pragma disables the generatio
31. stack is already in use for f e many return addresses 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 developed in ANSI C 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 the int long reent compiler option 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 Also see section 3 7 about Overlaying and section 3 10 about Functions using private register banks 3 8 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 interrupt vector table 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 If the in
32. these questions may help you to avoid burnout Chances are you didn t want to hear some of them burnout is bad for electronic devices programmers and motorcycle tyres 67 Chapter 7 Support SDCC has grown to be a large project The compiler alone without the preprocessor assembler and linker is well over 100 000 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 download area and cvs 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 reports 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 t
33. to this variable generates the assembly code D2 00 setb _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 bitfields without an explicit signed modifier are implemented as unsigned Not really meant as examples but nevertheless showing what bitfields are about device include mc68hc908gy h and sup port regression tests bitfields c 29 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 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 16 bit special function register combination for timer 0 with the high byte at location 0x8C and the low byte at location 0x8A sfrl6 at 0x8C8A TMRO sbit at 0xd7 CY CY Carry Flag 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 de clared using sfr16 or sfr32 Allthough SDCC usually accesses them Least Significant Byte LSB first this is
34. use of defines with inline assembly HC08 define CLI _asm cli endasm define SEI _asm sei 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 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 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 36 3 10 FUNCTIONS USING PRIVATE REGISTER BANKS MCS51 DS390 CHAPTER
35. 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 a _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 option no xinit opt and section 4 1 about MCS51 variants 2possible exception if a function is called ONLY from interrupt 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 37 3 12 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC 3 11 2 HCOS Startup Code The HCO8 startup code follows the same scheme as the MCS51 startup code 3 11 3 Z80 Startup Code On the Z80 the startup code is inserte
36. 00 END 0x200007 PROTECTED CODEPAGE AME config START 0x300000 END 0x30000D PROTECTED CODEPAGE AME devid START 0x3FFFFE END 0x3FFFFF PROTECTED CODEPAGE AME eedata START 0xF00000 END 0xF000FF PROTECTED ACCESSBANK NAME accessram START 0x0 END 0x7F DATABANK AME gpr0 START 0x80 END 0xFF DATABANK AME lt gprl START 0x100 END 0x1FF DATABANK AME gpr2 START 0x200 END 0x2FF DATABANK AME gpr3 START 0x300 END 0x3FF DATABANK AME gpr4 START 0x400 END 0x4FF DATABANK AME gpr5 START 0x500 END 0x5FF ACCESSBANK NAME accesssfr START 0xF80 END 0xFFF PROTECTED SECTIO AME CONF IG ROM config SECTIO AME bank0 RAM gpr0 these SECTION directives SECTIO AME bank1 RAM gpr1 should be added to link SECTIO AME bank2 RAM gpr2 section name bank with SECTIO AME bank3 RAM gpr3 a specific DATABANK name SECTIO AME bank4 RAM gpr4 SECTIO AME bank5 RAM gpr5 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 4 6 7 Header Files There is one main header file that can be included to the source files using the picl6 port That file is the pic18fregs 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 p
37. 3 USING SDCC 3 9 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 10 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 make 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 o
38. 3 mul 0 14 compiler detects i j to be induction variables 15 for i lt 0 j lt 10 i lt 10 itt j 16 sum 1 17 mul i 3 this multiplication remains 18 gint j 3 this multiplication changed to addition 19 20 return sumtmul 21 In addition to the operands each Code 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 Code Execution sequence number ICode hash table key loop depth of the iCode Then follows the human readable form of the ICode operation Each operand of this triplet form can be of three basic types a compiler generated temporary b user defined variable c a constant 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 iCode with sequence number 5 For induction variables such as iTemp21 the live
39. 599 amp atid 350599 68 7 3 SUBMITTING PATCHES CHAPTER 7 SUPPORT 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 mod ified more than one file a patch created fe with diff Naur unmodified directory modified 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 lucky 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 if you re seriously using SDCC please consider subscribing to the lists 7 5 ChangeLog You can follow the status of the cvs version of SDCC by watching the Changelog in the cvs repository http cvs sf net cgi bin viewcvs cgi checkout sdcc sdcc ChangeLog rev HEADecontent type text plain 7 6 Release policy Historically there often were long delays between official releases and the sourceforge download area tends t
40. 6 2 3 Linking Options nodefaultlibs do not link default libraries when linking no crt Don t link the default run time modules use crt Use a custom run time module instead of the defaults 4 6 2 4 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 compiled pcode verbose Enable pcode debugging information in translation denable peeps Force the usage of peepholes Use with care gstack Trace push pops for stack pointer overflow call tree dump call tree in calltree file 4 6 3 Enviromental Variables There is a number of enviromental 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 functions that perform heavy use of bitfields ie 80 bytes of code space are saved when compiling m
41. 8 int 17 r0 Oxle int mov r7 0x1E mov r0 0x00 forcond_0 4 001048 iTemp 13 1r25 26 char CC iTemp21 lr21 38 short r4 lt Oxa short if iTemp13 lr25 26 charj CC 0 goto _forbreak_0 7 clrc mov a r4 xrl a 0x80 subb a 0x8a jnc 00107 00115 iTemp2 Ir18 40 short r2 iTemp2 lr18 40 short r2 iTemp21 lr21 38 short 14 mov a r4 add a r2 mov r2 a iTemp15 Ir29 30 short r1 iTemp21 lr21 38 short r4 0x3 short mov b 0x03 mov a r4 mul ab mov rl a iTemp11 Ir19 40 short r3 iTemp11 lr19 40 4 short 13 iTemp15 Ir29 30 short rl add a r3 mov r3 a 84 9 2 A FEW WORDS ABOUT BASIC BLOCK SUCCESSORS PREDEMABSOR Y ANDMDOMINANORRNA LS iTemp17 lr23 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 HOxff mov r0 a _gint 1r0 0 int _gint lr0 0 int iTemp17 lr23 38 int r7 r0 mov a r7 add a _gint mov _gint a mov a r0 addc a _gint 1 mov _gint 1 a Temp21 lr21 38 short r4 iTemp21 lr21 38 short r4 0x1 short inc r4 iTemp23 1r22 38 int r5 r6 lt 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 4short mov a r3 add a r2 mov dpl a _return 8 00108 ret 9 2 A few words about basic block successors predecessors
42. AA eR ew A a tepe A Ji 48 4A The COS PON sou sc Se pS EA AAS a p HS ES GS SS ee aS 49 45 TE PIA po sis A ee eH ee Pa eee ee ee RHEE eee eee es 49 4 5 1 C code and 14bit PIC code pageandRAMbanks 49 452 Creating a device linci de Tile 22 64455645 bee eR we deja 49 O e RR 49 ASA Linke ana assemble cee ke AE RE ERS A a As 49 ASS COMBATE PUDE 2 66 64446 202 8 A Ee ee te BA SEES ere BH wg 50 S30 TREDI ss 6 ck ne be ee eae be Ob Se eee k God be Hee cone 4 50 4 5 6 1 error missing definition for symbol __gptrgetl 50 4562 Processor mismatch i tle XXX vii a des ss Re ORES 50 45 7 Know DRES oso a wa eee a be a ee ee eh eee oe a ee ewe e 50 O TAGE IAA onc II 50 46 The PCG pot occ etec tco ee a hea Oe deo RA ewe ee ee Ji 50 46 1 Global Options o srba ee ee RA ee BS a Gea a wo 51 4 6 2 Port Specific OpHons sss c 244 5884 ee be bee ries eee ee eS 51 A o OPONE AA Sad be aie Med ke ea PEERS Ged as 51 4622 Optimization OpPHONS gt p 04 pos RR 51 525 lambing CIO 6 rr ee AS BEER DPSS S 52 4624 Debugging Options lt oe coses 84 kee oa wR SEY OE HS 52 A03 Enviromental Variables sir ls eae ce BOGE A et ew 52 464 Preprocessor Mactos sb alee A AE RR ee EGA 52 46 3 Directories lt lt lt oo bc ee bee eee eee ea bee ee ee ea 53 AGO Promis ss ee Bs de Re a eh skl By bi a Se ha ie Je els 53 4 6 7 Header Files 0405528 ee 0s ae bee Ree HAS See ee eee ee be ae ee PS 54 AGS ie 2 oasis A A d
43. C 11 Byte swapping 75 C Reference card 67 Carry flag 30 Changelog 69 code 23 26 29 code banking limited support 7 code page pic 14 49 Command Line Options 21 Compatibility with previous versions 6 Compiler internals 81 Copy propagation 71 critical 36 cvs code repository 68 Cyclomatic complexity 26 79 data hc08 storage class 32 data mcs51 ds390 storage class 23 28 31 DDD debugger 63 ddd debugger 67 Dead code elimination 27 70 83 Debugger 19 61 Defines created by the compiler 47 DESTDIR 10 Division 34 35 Documentation 66 double not supported 79 download 68 doxygen source documentation tool 67 DPTR 41 48 75 DPTR DPH DPL 41 DS390 memory model 45 DS390 options 24 DS80C390 21 DS80C400 21 ELF format 23 Emacs 64 Endianness 75 Environment variables 27 Examples 69 External stack mcs51 44 far storage class 28 38 Feature request 7 68 Flags 30 Flat 24 DS390 memory model 45 Floating point support 35 43 79 fpga field programmable gate array 15 function epilogue 25 39 function parameter 33 41 42 function prologue 25 39 45 gbz80 GameBoy Z80 21 48 gdb 61 89 getchar 44 Global subexpression elimination 27 GNU General Public License GPL 6 GNU Lesser General Public License LGPL 44 gpsim pic simulator 67 gputils pic tools 49 67 HC08 21 49 HD64180 31 Higher Order Byte 76
44. 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 now no pack iram Causes the linker to use old style for allocating memory areas 23 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC 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 princip
45. LIB SDCC_LIB lt model gt lt model gt lt model gt SDCC_HOME SDCC_HOME SDCC_HOME lib PREFIX2DATA DIR share sdec lt model gt LIB DIR SUFFIX lt model gt lib lt model gt path argv 0 path argv 0 path argv 0 BIN2DATADIR sdcc lib lt model gt Mlib lt model gt LIB_DIR SUFFIX lt model gt DATADIR usr local share sdcc not on Win32 LIB DIR SUFFIX lt model gt lib lt model gt The option nostdlib disables the last two search paths 2 4 Building SDCC 2 4 1 Building SDCC on Linux 1 Download the source package either from the SDCC CVS repository or from the nightly snapshots it will be named something like sdcc src tar gz 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 xvzf sdcc src tar gz this will create a sub directory called sdec with all of the sources Change directory into the main SDCC directory for example type cd sdec 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 a a ura 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 11 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC 2 4 2 Building SDCC on OSX 2 x Follo
46. ON CHAPTER 2 INSTALLING SDCC 2 5 Building the Documentation If the necessary tools LyX BIEX IXATEX2HTML are installed it is as easy as changing into the doc directory and typing make there You re invited to make changes and additions to this manual sdec doc sdceman lyx Using LyX http www 1lyx org as editor this 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 sdecman 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 information 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 we expect you to have a quic
47. PTER 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 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 lt Where is Figure II gt ICode Example This section shows some details of iCode The example C code does not do anything useful it is 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 5 short function data int x 6s 7 short i 10 dead initialization eliminated 8 short sum 10 dead initialization eliminated 9 short mul 10 int j 11 while x x ptt T2 sum 0 1
48. SDCC Compiler User Guide SDCC 2 5 4 Date 2005 11 17 18 25 51 Revision 1 128 Contents 1 Introduction LI AM SIN chee hk ae o a a aw a A a e OA 12 A NR 13 Typographic convennans a eo a A AAA AA eS RAE HESS 14 Compatibilty with previdls VESNE oc see a A RA LA NS RS QUIEMBS 00 es A AS be be AAA AS 1G ther Resonis gt ps eae be ee uda pole a eee ee Bb 1 7 Wishes forthe TIME socios 684400445888 4 ede eA aA ve ob eo 2 Installing SDCC 21 Contes OMAN s sy pik Ks a RR AR ERG A aa A BE RR EVA 2 MSI AS cn rd ee eee oe ee ek a ee a Ee oe ed RS SOMO PAINS oi eee eS Ce Ee eee SESE BAS Sees BES 2A Buking SDE lt lt ow cay nee sO Re Oe ee ORR a wa RG Se E Oe Zali Amina DOCCOL sido hed RSS G Se PRS EBS eee Se AA 6 22 Building SDCC Om USA ZE se aa ee ee pe RE ERR PORN Ole we eS 2 4 3 Cross compiling SDCC on Linux for Windows 244 Building SDCC on Windows lt sc sechas esea Oe smo ew JR ee 2 4 5 Building SDCC using Cygwin and Mingw32 2 4 6 Building SDCC Using Microsoft Visual C 6 0 NET MSVC 2 4 7 Building SDCC Using Borland e 2 4 8 Windows Install Using a ZIP Package 2 4 9 Windows Install Using the Setup Program 29 Building he Documenta es s sace ss Roe a Me HB Gene ee A a 20 Reading the Documentation socias bo ee Re ERR PEEKS A za Tes ng ihe DEL Compiler lt i t bie e be A oe hae RES 2 8 In
49. 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 ISR 4 6 12 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 56 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 13 Interrupts An interrupt servive routine ISR is declared using the interrupt keyword void isr void n is the interrupt number which for PIC18F devices can be interrupt n 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 genetated 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 spa
50. TED PROCESSORS 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 properly 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 0x100 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 11 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 the high part of a is stored in FSR2 2 or 3 for large stack model This keyword replaces the deprecated wparam pragma shadowregs When entering exiting an ISR it is possible to take advantage of the PIC18F hardware shadow registers which hold the values of WREG
51. 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 the 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 include lt stdio h gt PUTCHAR c PORTA c void main void stdout printf This is a printf test nl STREAM_USER dump character c to PORTA this is not necessery since stdout points by default to STREAM_USER 58 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 15 2 Printing functions PIC16 contains an implementation of the printf family of functions There exist the following functions extern unsigne
52. 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 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 or Atmel AVR SDCC allows MCU specific storage class extensions i 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 or ATMEL AVR C 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 Code 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 compile
53. _at 30 33 38 88 _ bit 29 _ code 29 _ critical 36 data hc08 storage class 32 __ data mcs51 ds390 storage class 28 31 __ds390 47 __endasm 38 41 __ far storage class 28 38 __hc08 47 __idata mcs51 ds390 storage class 28 31 __ interrupt 31 34 40 _ mes5l 47 __ naked 39 45 _ near storage class 28 pdata mcs5 1 ds390 storage class 29 __sbit 6 30 sfr 30 31 __sfr16 30 __sfr32 30 __using mcs51 ds390 register bank 31 34 35 37 __xdata hc08 storage class 32 __xdata mcs51 ds390 storage class 28 31 32 __ 280 47 _asm 36 38 40 _endasm 36 38 41 _naked 39 45 _sdcc_external_startup 37 8031 8032 8051 8052 mcs51 CPU 5 Absolute addressing 32 33 ACC mces51 ds390 register 41 Aligned array 32 38 Annotated syntax tree 81 ANSI compliance 6 78 Any Order Bit 75 AOMF AOMFS1 19 25 aslink 5 66 Assembler documentation 39 66 Assembler listing 19 Assembler options 26 Assembler routines 36 38 41 77 Assembler routines non reentrant 41 Assembler routines reentrant 42 Assembler source 19 asXXXX as gbz80 as hc08 asx8051 as z80 5 39 66 at 30 33 38 atomic 34 37 AVR 22 B mcs51 ds390 register 41 Basic blocks 27 85 bit 6 23 29 30 32 33 Bit rotation 74 Bit shifting 74 Bit toggling 6 bitfields 29 INDEX INDEX block boundary 32 Bug reporting 68 Building SDC
54. _endasm 40 3 13 INTERFACING WITH ASSEMBLER CODE CHAPTER 3 USING SDCC Inline assembler code cannot reference any C Labels however it can reference labels defined by the inline assem bler e g foo some c code _asm some assembler code ljmp 0003 _endasm some more c code clabel inline assembler cannot reference this label _asm 0003 label can be referenced by inline assembler only _endasm some more c code 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 3 13 Interfacing with Assembler Code 3 13 1 Global Registers used for Parameter Passing The compiler always uses the global registers DPL DPH B and ACC to pass the first parameter to a routine 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 3 13 2 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
55. _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 12 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 s3 gt 3The assembler does not like some characters like or in comments You ll find an 100 pages assembler manual in sdec as doc asxhtm html 39 3 12 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC 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
56. a a Bape edo Gs 54 4 6 9 Memory Models lt s aes trwa cores cado A A 55 MOM A 55 OLI Practis vi an LR ree Ke ee SE She ew A See a E RA 56 4 6 12 Function returni Values 5 4 38 6 hed si a Oe eR Re More 56 MOIS IMETI seeped dge ee SR Re eR OE EER OR OR a a OS 57 4 6 04 Cenenc POMEN 624544452 a ee ee eee VE AAA 57 46 15 PICIGC Libraries cc ee secta as a A eee 8 58 4 6 15 1 Standard VO Streams coo deso eS 58 2132 PRADOS NUNE NONE cios LG OR Ba a AGE Bae ee ew Go 59 4615 3 SION i sed cb G awe AG boa ea A wd bee 59 4016 PICIO Poth Tips oscar a SEES RE EMERG ES 60 AGIGI SHES ok co Be eRe kK OR AY ae Ge See RA 60 CONTENTS CONTENTS 5 Debugging with SDCDB 5 1 Compiling for Debugging 3 2 How the Debugger Works sopas ras sra RE E JK kle 5 3 Startimes the DEDUSSET ooo eee eee be tress Sa Command Late UOPROAS c ee t 6246 eds b SA Se bd be wae eis a2 DebuseerCouimiged o bee a ee ee bok bs S0 temacie with DDD s i o eS CRN Be eee ea hea ELE a Inberdieme wiii XEDA o coe es kG oe e ER RO ee A elja 6 TIPS 6 1 Toolsincludedinthedistribution 6 2 Documentation included in the distribution 6 3 Related open source tools se s ee ee we 6 4 Related documentation recommended reading 63 SOME OVSRIORS cocidos cr aa a E a 7 Support 71 Reporting Bugs esec rer a eta ra a ee ew es ta Requesting Features ios ca RS Re a ee T3 Sabini patche
57. ace 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 extern volatile bit MISO master in slave out extern volatile bit MCLK master clock Input and Output of a byte on a 3 wire serial bus If needed adapt polarity of clock polarity of data and bit order unsigned char spi_io unsigned char out_byte unsigned char i 8 do MOSI out_byte amp 0x80 out_byte lt lt 1 MCLK 1 _asm nop _endasm for slow peripherals if MISO out_byte 1 MCLK 0 while i 32 3 6 PARAMETERS amp LOCAL VARIABLES CHAPTER 3 USING SDCC return out_byte Then someplace in the code for the first hardware you would use bit at 0x80 MOSI 1 0 port 0 bit 0 bit at 0x81 MISO 1 0 port 0 bit 1 bit at 0x82 MCLK 1 0 port 0 bit 2 Similarly for the second hardware you would use bit at 0x83 MOSI I O port 0 bit 3 bit at 0x91 MISO I O port 1 bit 1 bit at 0x92 MCLK I O port 1 bit 2 and you can use the same hardware dependent routine without chan
58. acing used in the project is 8 Although a tabulator spacing of 8 isa 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 6 Building SDCC Using Microsoft Visual C 6 0 NET MSVC Download the source package either from the SDCC CVS repository or from the nightly snapshots http sdec sourceforge net snap php it will be named something like sdcc src tgz SDCC is dis tributed with all the projects workspaces and files you need to build it using Visual C 6 0 NET except for sdedb exe which currently doesn t build under MSVC The workspace name is sdcc dsw Please note that as it is now all the executables are created in a folder called sdcc bin_vc Once built you need to copy the executables from sdec bin vc to sdec bin before running SDCC WARNING Visual studio is very picky with line terminations it expects the 0x0d Ox0a DOS style line endings not the 0x0a Unix style line endings When using the CVS repository it s easiest to configure the cvs 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 o
59. alloc c with this option NO_REG_OPT do not perform pCode registers optimization This should be used for debugging purposes In some where bugs in the pcode optimizer are found users can benefit from temporarily disabling the optimizer until the bug is fixed 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 nnn 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 52 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 5 Directories PIC16 port uses the following directories for searching header files and libraries Directory Description Target Command prefix PREFIX sdec include pic16 PIC16 specific headers Compiler I PREFIX sdcc lib pic16 PIC16 specific libraries Lin
60. an those iTemp 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 Phase five is register allocation There are two parts to this process The first part I call register packing for 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 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 As mentioned in the optimization section the peep hole optimizer is rule based system which can repro grammed for other MCUs 80 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
61. any storage class storage classes for parameters will be ignored their allocation is governed by the memory model in use and the reentrancy options 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 33 3 7 OVERLAYING CHAPTER 3 USING SDCC 3 7 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 explicit storage class is specified for a local variable it will NOT be overlayed 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
62. aries 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 17 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 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 WI r on the SDCC command line However currently the linker can not handle code
63. 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 sdedb gt clear 100 sdcdbsclear foo c 100 sdedb 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 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 info registers show content of all registers 62 5 6 INTERFACING WITH DDD CHAPTER 5 DEBUGGING WITH SDCDB 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 file 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 followi
64. ay mov r3 _head inc _head mov dpl r3 mov dph _buf gt gt 8 mov a r2 movx dptr a 001038 ret _endasm The new file buffer c should compile with only one warning about the unreferenced function argument c Now we hand optimize the assembly code and insert an define USE_ASSEMBLY 1 and finally have 38 3 12 INLINE ASSEMBLER CODE CHAPTER 3 USING SDCC 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 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 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_ends i buf headtt 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 movx dptr a inc _head we could do an ANL head 40x0f here to use a smaller buffer see above t_b_end restore used registers here _endasm endif The inline assembler code can contain any valid code understood by the assembler this includes any assembler di rectives and comment lines The compiler does not do any validation of the code within the asm
65. ble ucsim host 1586 mingw32msvc build unknown unknown 1inux gnu To cross compile on Cygwin for Mingw32 see also sdec support scripts sdec cygwin mingw32 configure C A CFLAGSz mno cygwin 02 A LDFLAGS mno cygwin A prefix sdcc A datadir sdec docdir sdcec doc include_dir_suffix include lib_dir_suffix lib A sdccconf_h_dir_separator A disable ucsim 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 EXEC PREFIX fusr local bin Usdec bin Include files DATADIR INCLUDE DIR SUFFIX usr local share sdec include sdcc include Library file DATADIR LIB DIR SUFFIX usr local share sdcc lib WsdccMib Documentation DOCDIR usr local share sdcc doc sdec doc 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 sdec Of course this doesn t change the search paths compiled into the binaries Moreover the install path can be changed by defining DESTDIR make install DESTDIR HOME sd
66. c contains some more functions foomain c contains more functions and the function main 19 3 1 COMPILING CHAPTER 3 USING SDCC 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 sdec 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 presented to it The linker is invoked from SDCC using a script file with extension lnk You can view this file to troubleshoot linking problems such as those arising from missing libraries 3 1 3 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 curre
67. cc 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 cvs only if you use CVS 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 bash login i 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC 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 sp
68. cc 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 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC 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 I dir I dir dir SDCC_INCLUDE SDCC_HOME SDCC_INCLUDE SDCC_ HOME SDCC_INCLUDE SDCC_HOME include PREFIX2DATA DIR share sdec INCLUDE DIR SUFFIX include path argv 0 path argv 0 path argv 0 include BIN2DATADIR sdec include INCLUDE DIR SUFFIX DATADIR INCLUDE DIR SUFFIX usr local share sdcc include not on Win32 The option nostdinc disables the last two search paths 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 L dir L dir L dir SDCC_LIB SDCC_
69. ccasionally be useful anyway pending I don t think this has been done yet An interrupt function using a non zero bank will assume that it can trash that register bank and will not save it 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 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 3 11 Startup Code 3 11 1 MCS51 DS390 Startup Code The compiler inserts a call to the C routine _sdec_external_startup at the start of the CODE area This routine is in the runtime library By default this routine returns 0 if this routine returns a non zero value the static amp global variable initialization
70. ce 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 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 interruptt s vector address and cause undeterminate program behaviour if that interrupt is raised n is possible to 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 4 6 14 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 descrption data 1 0 uuuuuu uuuuxxxx xxxxxxxx a 12 bit data pointer in data RAM memory code 0 0 UXXXXX XXXXXXXX xxxxxxxx a 21 bit code pointer in FLASH memory eeprom 0 1 uuuuuu uuuuuuxx xxxxxxxx a 10 b
71. ch 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 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 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
72. d by linking with crt0 o 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 o 3 12 Inline Assembler Code 3 12 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 unsigned char far at 0x7f00 buf 0x100 unsigned char head tail void to buffer unsigned char c if head tail 1 buf head c access to a 256 byte aligned array If the code snippet 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 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 _asm mov r2 dpl buffer c if head tail 1 mov a _tail dec a mov r3 a mov a head cjne a ar3 00106 ret 00106 buffer c buf head c access to a 256 byte aligned arr
73. d int sprintf char buf char fmt extern unsigned int vsprintf char buf char fmt va_list ap extern unsigned int printf char fmt extern unsigned int vprintf char fmt va_lista ap extern unsigned int fprintf FILE fp char fmt extern unsigned int vfprintf FILE fp char fmt 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 necessery buffer For fprintf and vfprintf fp should be a stream pointer i e stdout STREAM_MSSP etc 4 6 15 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 descritpion SIG_RB PORTB change interrupt SIG_EE EEPROM FLASH write complete interrupt SIG_INTO INTO external interrupt SIG_BCOL Bus collision interrupt SIG_INT1 INTI 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 TMRI overflow interrupt SIG_MSSP SSP receive transmit interrupt SIG_TMR2 TMR2 matches PR2 interrupt SIG_TMR3 TMR3 overflow inte
74. 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 See file sdec as doc asxhtm html for 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 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 linker 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 xstack Uses a pseudo stack in the first 256 bytes in the external ram for allocating variables and passing parameters See section 3 17 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
75. e extra stack 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 amp optimizations for a given function pragmas should be placed before and or after a function placing pragma s inside a function body could have unpredictable results pragma save save the current settings pragma nogcse turnoff global subexpression elimination pragma noinduction turn off induction optimizations int foo large code pragma restore turn the optimizations back on The compiler will generate a warning message when extra space is allocated It is strongly recommended that the save and restore pragma s be used when changing options for a function 46 3 19 DEFINES CREATED BY THE COMPILER CHAPTER 3 USING SDCC 3 19 Defines Created by the Compiler The compiler creates the following defines define Description SDCC this Symbol is always defined SDCC mes5l or SDCC_ds390 or SDCC_z80 etc depending on the model used e g mds390 __mces51 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_USE_XSTACK when xstack opt
76. e following expression to be a left bit rotation unsigned char i unsigned is needed for rotation i li lt lt 1 i gt gt 7 will generate the following code SDCC uses pattern matching on the parse tree to determine this operation Variations of this case will also be recognized as bit rotation i e i i gt gt 7 i lt lt 1 left bit rotation 74 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 1 gt gt 4 j lt j lt lt 8 3 gt gt 8 and generates a swap instruction for the nibble swapping or move instructions for the byte swapping The j 99299 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 fo O O
77. e pic16 port sdec src pic16 NOTES SDCC internal documentation debugging file format sdec doc cdbfileformat pdf 66 6 3 RELATED OPEN SOURCE TOOLS CHAPTER 6 TIPS 6 3 Related open source tools Name Purpose Where to get gpsim PIC simulator http www dattalo com gnupic gpsim html gputils GNU PIC utilities http sourceforge net projects gputils fIPS PIC programmer http freshmeat net projects flp5 indent Formats C source Master of the http directory fsf org GNU indent html white spaces srecord Object file conversion checksum http sourceforge net projects srecord ming objdump Object file conversion Part of binutils should be there anyway doxygen Source code documentation sys http www doxygen org tem kdevelop IDE has anyone tried integrating http www kdevelop org SDCC amp sdedb Unix only splint Statically checks c sources see http www splint org 3 2 8 ddd Debugger serves nicely as GUI to http www gnu org software ddd sdcdb Unix only 6 4 Related documentation recommended reading Name Subject Title Where to get c refcard pdf C Reference Card 2 pages http refcards com refcards c index html c faq C FAQ list http www eskimo com scs C faq top html Latest datasheet of the target CPU vendor Revision history of datasheet vendor S S Muchnick Advanced Compil
78. ed SDCC also provides an option cyclomatic to report the relative complexity of a function These func tions can then be further optimized or hand coded in assembly if needed SDCC also comes with a companion source level debugger SDCDB the debugger currently uses ucSim a freeware 1 2 OPEN SOURCE CHAPTER 1 INTRODUCTION simulator for 8051 and other micro controllers SDCDB and ucSim are currently not available on Win32 platforms The latest version can be 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 open source and freeware source code for all the sub packages pre processor assemblers linkers etc is distributed with the package This documentation is maintained using a freeware 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 Sof
79. eee 23 323 D53907 IDA OPI i s i e ie Bey pee Bie be Hae Ba eS a eds Had es 24 320 ZOPOPHORE os int bdo bes po be hae eb eee ba ee ee od 4 24 dje Kiplmiizaton PRONG oo ok Se RS ORES EAS BA wee ES be k 24 32e Ober OPMS cos A A a ee a Re See oe ee 25 32 9 Intermediate Dump Options s eaea etka ea ie SEBE A neds 27 3 2 10 Redirecting output on WindowsShells 27 Environment variables lt evos 566s eR REE Ee ee ee 27 Storage Class Language Extensions 28 3 4 1 MCS51 DS390 Storage Class Language Extensioms 28 IALL MA RA sng a eb LAS Ba G os be Re eae ee seda Gos 28 SANS RAMA MA a a ee Pea we ea Ge ee ed 28 Sees AAO A E 28 IALA PS cla x AA ee ek ee SO She e a a Bee 29 Sel As God A II BK Oe E ie 29 SAA BI ee eee OR AAA Oe ee a RS 29 SecA lt P SOLE Re SBI A ee eA ME eee Pe bee 30 3 4 1 8 Pointers to MCS51 DS390 specific memory spaces 30 3 4 1 9 Notes on MCS51 memory layout 30 3 4 2 Z80 Z180 Storage Class Language Extensions 31 3 4 2 1 sfr in out to 8 bit addresses 31 3 4 2 2 banked sfr in out to 16 bit addresses 31 3 4 2 3 sfr in0 out0 to 8 bit addresses on ZI80 HD64I80 31 3 4 3 HCO8 Storage Class Language Extensions 000 lt lt 32 IAE ANN 32 See Ra oe GA E SA A bee A Ee 32 Abeolute Addressing o coace
80. embler 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 8 Other Options 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 must 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 o lt path file gt The output path resp file where everything will be placed If the parameter is a path it must have a trailing slash or backslash for the Windows binaries to be recognized as a path stack auto All functions in the source file will be compiled as reentrant i e the parameters and local variables will be allocated on the stack See section 3 6 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
81. epilogue For example compare the code generated by these two functions volatile data unsigned char counter void simpleInterrupt void interrupt 1 counter void nakedInterrupt void interrupt 2 _naked _as 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 simplelnterrupt looks like _simpleInterrupt push acc push b push dpl push dph push psw mov psw 40x00 inc _counter pop psw pop dph pop dpl pop b pop acc reti whereas nakedlnterrupt 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 2 3 Use of Labels within Inline Assembler SDCC allows the use of in line assembler with a few restrictions regarding labels In older versions of the compiler all labels defined within inline assembler code had to be of the form nnnnn where nnnn is a number less than 100 which implies a limit of utmost 100 inline assembler labels per function _asm mov b 10 000015 djnz b 00001
82. er Design and bookstore very dedicated probably read other books first Implementation 6 5 Some Questions Some questions answered some pointers given it might be time to in turn ask you some questions e 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 e 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 e 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 test software update mechanism patent issues e is your project adequately positioned in that magic triangle fame fortune fun your proj q yp g g Maybe not all answers to these questions are known and some answers may even be no nevertheless knowing
83. es 16 bit ints Therefore the results are different From comp lang c FAQ If well defined overflow characteristics are important and negative values are not or if you want to steer clear of sign extension problems when manipulating bits or bytes use one of the correspond ing 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 65 6 1 TOOLS INCLUDED IN THE DISTRIBUTION CHAPTER 6 TIPS 6 1 6 2 NEVER jump into a LOOP Declare the variables to be local whenever possible especially loop control variables induction Since the compiler does not always do implicit integral promotion the programmer should do an explicit cast when integral promotion is required Reducing the size of division multiplication amp modulus operations can reduce code size substantially Take the following code for example foobar unsigned int pl unsigned char ch o unsigned char chl lt pl ch For the modulus operation the variable ch will be promoted to unsigned int first then the modulus operation wi
84. es 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 sdec The compiler e sdcpp The C preprocessor e asx8051 The assembler for 8051 type processors e as z80 as gbz80 The Z80 and GameBoy Z80 assemblers aslink The linker for 8051 type processors e link z80 link gbz80 The Z80 and GameBoy Z80 linkers e s51 The ucSim 8051 simulator Not available on Win32 platforms e sdcdb The source debugger Not available on Win32 platforms e packihx A tool to pack compress Intel hex files In lt installdir gt share sdcc include e the include files In lt installdir gt share sdcc lib e the subdirs src and small large z80 gbz80 and ds390 with the precompiled relocatables In lt installdir gt share sdcc doc e the documentation As development for other processors proceeds this list will expand to include executables to support processors like AVR PIC etc 2 9 1 sdec 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 preprocessor The C preprocessor is used to pull in include sources process ifdef statements defines and so on 2 9 3 asxxxx as
85. ges 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 6 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 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 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 unsigned char i bit bvar data at 0x31 unsigned char j In the above example the variable i will be allocated in the external ram bvar in bit addressable 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 Parameters however are not allowed
86. globl _asm_func area OSEG asm_func_PARM_2 adst area CSEG _asm_func mov a dpl add a _asm_func_PARM_2 mov dpl a mov dph 0x00 ret 41 3 13 INTERFACING WITH ASSEMBLER CODE CHAPTER 3 USING SDCC Note here that the return values are placed in dpl One byte return value dpl LSB amp dph MSB for two byte values dpl dph and b for three byte values generic pointers and dpl dph b amp acc for four byte values 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 dpl for a one byte parameter dptr for two bytes b dptr for three bytes and acc b dptr for a four bytes parameter The variable name for the second parameter will be lt function name gt PARM 2 Assemble the assembler routine with the following command asx8051 losg asmfunc asm Then compile and link the assembler routine to the C source file with the following command sdec cfunc c asmfunc rel 3 13 3 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 after the call the leftmost parameter will be on the top of the stack Here is an example extern int asm_func unsigned char unsigned char int c func unsigned char i unsigned char j reentrant return asm func
87. gt 23 31 code size lt Value gt 23 31 codeseg lt Value gt 26 compile only 25 constseg lt Value gt 26 cyclomatic 26 data loc lt Value gt 23 31 debug 19 21 25 52 61 disable warning 26 dumlrange 27 dumpall 27 68 dumpdeadcode 27 dumpgcse 27 dumploop 27 dumplrange 27 dumprange 27 dumpraw 27 dumpregassign 27 float reent 26 i code in asm 26 idata loc lt Value gt 23 int long reent 25 35 43 Iram size lt Value gt 23 31 37 less pedantic 26 lib path lt path gt 22 main return 26 model flat24 24 model large 23 44 model medium 23 model small 23 87 no c code in asm 26 no pack iram 23 no peep 25 no peep comments 26 no std crt0 24 38 no xinit opt 24 37 nogcse 24 noinduction 24 noinvariant 24 nojtbound 24 nolabelopt 24 noloopreverse 24 nooverlay 25 nostdinc 26 nostdlib 26 opt code size 25 opt code speed 25 out fmt ihx 23 out fmt s19 19 23 pack iram 23 peep asm 25 39 peep file 25 77 print search dirs 16 26 protect sp update 24 stack 10bit 24 stack auto 24 25 33 35 43 44 46 78 stack loc lt Value gt 23 31 stack probe 24 stack size lt Value gt 23 std c89 26 79 std c99 79 std sdcc89 26 std sdcc99 26 tini libid 24 use accelerator 24 use stdout 26 27 vc 26 27 verbose 26 xdata l
88. he C source and at the ASM source level Sdcdb is currently not available on Win32 platforms 5 1 Compiling for Debugging The debug option must be specified for all files for which debug information is to be generated The complier 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 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 5 3 Starting the Debugger The debugger can be started using the following command line Assume the file you are debugging has the file name foo sdcdb foo 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 5 4 Command Line Options e directory lt source file directory gt thi
89. he 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 maker 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 sdec 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 reporting bugs http sourceforge net tracker group_id 599 amp atid 100599 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
90. his with an example replace 13mp 5 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 the name labellnRange 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 bellnRange 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 labellsReturnOnly 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 Deviations from the compliance e 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 other and can
91. ic18fregs h automatically so the same source can be used with a variety of devices 4 6 8 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 gputils 54 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS Building the libraries Before using SDCC pic16 there are some libraries that need to be compiled This process is not done automatically by SDCC since not all users use SDCC for pic16 projects So each user should compile the libraries separately The steps to compile the pic16 libraries under Linux are cd device lib picl configure make ed ax make model picl6 su c make install install the libraries you need the root password If you need to install the headers too do cd device include su c make install install the headers you need the root password There exist a special target to build the I O libraries This target is not automatically build because it will build the I O library for every supported device This way building will take quite a lot
92. ion is used SDCC_STACK_TENBIT when mds390 is used SDCC_MODEL_FLAT24 when mds390 is used 47 Chapter 4 Notes on supported Processors 4 1 MCSSI variants MCSS51 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 is 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 0x92 _XPAGE Cypress EZ USB family sfr at Oxaf _XPAGE some Silicon Labs Cygnal chips sfr at Oxaa _XPAGE some Silicon Labs Cygnal chips For more exotic implementations further customizations may be needed See section 3 11 for other possibilities 4 1 2 Other Features available by SFR Some MCS51 variants offer features like Double DPTR multiple DPTR decrementing DPTR
93. it eeprom pointer in EEPROM memory unimplemented 1 1 XXXXXX XXXXXXXX XXXXXXXX Uunimplemented pointer type Generic pointer are read and written with a set of library functions which read write 1 2 3 4 bytes 2This 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 interruptt s vector address 3NOTE that when the _naked attribute is specified for an interrupt routine then NO registers are stored or restored 57 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4 6 15 PIC16 C Libraries 4 6 15 1 Standard I O Streams In the stdio h the type FILE is defined as typedef char 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 FII extern FII LE stdin LE 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 nnnn 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
94. izations 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 not 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 24 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 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 ass
95. k 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 sdec version at the prompt and the program should run and tell you the version If it doesn t run or gives a message about not finding sdcc program then you need to check over your installation 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 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 char test void main void 1 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
96. ker L 4 6 6 Pragmas PIC16 port currently supports the following pragmas stack pragma stack forces the code generator to initialize the stack amp frame pointers at a specific address This is an adhoc 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 initializes stack of 100 bytes at RAM address 0x200 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 wparam This pragma is deprecated Its use will cause a warning message to be issued code place a function symbol at static FLASH address Example place function test_func at 0x4000 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
97. le this should work with the stack auto 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 3 2 6 Z80 Options callee saves be Force a called function to always save BC no std ertO When linking skip the standard crt0 o object file You must provide your own crt0 o for your system when linking 3 2 7 Optimization Options nogese 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 optim
98. link link xxx The Assemblers and Linkage Editors This is retargettable assembler amp linkage editor it 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 2 9 4 s51 The Simulator S51 is a freeware opensource simulator developed by Daniel Drotos The simulator is 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 and the Phillips XA51 family S51 is currently not available on Win32 platfors 2 9 COMPONENTS OF SDCC CHAPTER 2 INSTALLING SDCC 2 9 5 sdedb Source Level Debugger Sdcdb is the companion source level debugger More about sdcdb in section 5 The current version of the debugger uses Daniel s Simulator S51 but can be easily changed to use other simulators Sdedb is currently not available on Win32 platfors 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 sdec 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 listi
99. ll be performed this will lead to a call to support routine _moduint and the result will be casted to a char If the code is changed to foobar unsigned int pl unsigned char ch o unsigned char chl unsigned char pl ch It would substantially reduce the code generated future versions of the compiler will be smart enough to detect such optimization opportunities Have a look at the assembly listing to get a feeling for the code generation Tools included in the distribution Name Purpose Directory uCsim Simulator for various architectures sdcc sim ucsim keil2sdcc pl header file conversion sdec support scripts mh2h c header file conversion sdec support scripts as gbz80 Assembler sdec bin as z80 Assembler sdec bin asx8051 Assembler sdec bin sdedb Simulator sdec bin aslink Linker sdec bin link z80 Linker sdec bin link gbz80 Linker sdec bin packihx ihx packer sdec bin Documentation included in the distribution Subject Title Where to get filename SDCC Compiler User Guide You re reading it right now Changelog of SDCC sdec Changelog ASXXXX Assemblers and ASLINK Relocating Linker sdec as doc asxhtm html SDCC regression test sdec doc test suite spec pdf Various notes sdec doc Notes on debugging with sdedb sdec debugger REA DME Software simulator for microcontrollers sdec sim ucsim doc index html Temporary notes on th
100. loating 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 you don t have to call this routines directly The compiler will use them automatically every time a floating point operation is required The floating point routines for the mes51 are implemented in assembler 43 3 16 LIBRARY ROUTINES CHAPTER 3 USING SDCC 3 16 Library Routines lt pending this is messy and incomplete a little more information is in sdcc doc libdoc txt gt 3 16 1 Compiler support routines _gptrget _mulint etc 3 16 2 Stdclib functions puts printf strcat etc 3 16 2 1 lt stdio h gt 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 You ll find examples for serial routines f e in sdec device lib The default printf implementation in print f_large c does not support float except on ds390 To enable this 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
101. ludes the XA51 port disable ucsim Disables configuring and building of ucsim disable device lib build Disables automatically building device libraries disable packihx Disables building packihx enable libgc Use the Bohem memory allocator Lower runtime footprint 8 2 1 CONFIGURE OPTIONS CHAPTER 2 INSTALLING SDCC 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 standard 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 reguired 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 Sourceforge s compile farm See the examples how to pass the Win32 se
102. n bugs 4 5 7 1 initialized data Currently data can only be initialized if it resides in the source file together with main Data in other source files will silently not be initialized 4 6 The PIC16 port The PIC16 port is the portion of SDCC that is responsible to produce code for the Microchip TM microcontrollers with 16 bit core Currently this family of microcontrollers contains the PIC18Fxxx and PIC18Fxxxx Currently supported devices are 50 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 18F242 18F248 18F252 18F258 18F442 18F448 18F452 18F458 18F1220 18F2220 18F2550 18F4331 18F4455 18F6520 18F6620 18F6680 18F6720 18F8520 18F8620 18F8680 18F8720 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 all callee saves All function arguments are passed on stack by default There is no need to specify this in the command line fommit 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 General Options General options enable certain port features and optimizations stack model model Used in conjuction with the command above Defi
103. n 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 e less_pedantic the compiler will not warn you anymore for obvious mistakes you r on your own now e disable_warning lt nnnn gt the compiler will not warn you anymore about warning number lt nnnn gt e 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 45 PRAGMAS CHAPTER 3 USING SDCC 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 obmitting the optional interrupt number after the interrupt keyword see section 3 8 about interrupts 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 optimiza
104. n 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 lI In order to build SDCC with MSVC you need win32 executables of bison exe flex exe and 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 a Create a directory were to put the tools needed or use a directory already present Say for exam ple C util 2 4 BUILDING SDCC CHAPTER 2 INSTALLING SDCC b Extract bison exe bison hairy bison simple flex exe and gawk exe to such directory WITHOUT preserving the original path
105. nes the stack model to be used valid stack models are small Selects 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 preplace udata with kword Replaces the default udata keyword for allocating unitialized data variables with wow om kword Valid keywords are udata_acs udata shr udata ovr ivt loc lt nnnn gt positions the Interrupt Vector Table at location lt nnnn gt Useful for bootloaders asm sets the full path and name of an external assembler to call link sets the full path and name of an external linker to call mplab comp MPLAB compatibility option Currently only suppresses special gpasm directives 4 6 2 2 Optimization Options optimize goto Try to 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 obanksel nn Set optimization level for inserting BANKSELs 0 no optimization checks previous used register and if it is the same then does not emit BANKSEL accounts only for labels 2 tries to check the location of even different symbols and removes BANKSEL s if they are in the same bank Important There might be problems if the linker script has data sections across bank borders 51 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS 4
106. never forget to use retfie for proper returning 4 6 16 PIC16 Port Tips Here you can find some general tips for compiling programs with SDCC pic16 4 6 16 1 Stack size The default stack size that is 64 bytes probably is enough 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 fommit frame pointer might reduce stack usage by not creating unnecessery stack frames Other ways to reduce stack usage may exist 60 Chapter 5 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 compiler installation which also builds and installs the debugger in the target directory specified during configuration The debugger allows you debug BOTH at t
107. ng 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 lam going Down My name is Bobby Brown 5 6 Interfacing with DDD The eps File http cvs sourceforge net viewcvs py checkout sdcc sdec doc figures ddd_example eps 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 63 5 7 INTERFACING WITH XEMACS CHAPTER 5 DEBUGGING WITH SDCDB 5 7 Interfacing with XEmacs Two files in emacs lisp are provided for the interfacing with XEmacs sdedb 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 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 file
108. ng the rule language The syntax for a rule is as follows rule replace restart lt assembly sequence gt n rye by ubi A Xn lt assembly sequence gt n 131 if lt functionName gt An 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 TI 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 1 e pop arl pop ar2 push ar2 push arl would result in pop arl 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 t
109. ng file updated with linkedit information created by linkage editor sourcefile sym symbol listing for the sourcefile created by the assembler sourcefile rel or sourcefile o Object file created by the assembler input to Linkage editor sourcefile 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 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 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 9 and section 9 1 Anatomy of the compiler 3 1 2 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
110. not be a return value from a function e g 78 8 3 CYCLOMATIC COMPLEXITY CHAPTER 8 SDCC TECHNICAL DATA struct s struct s sl s2 foo bt sl s2 is invalid in SDCC although allowed in ANSI struct s fool struct s parms invalid in SDCC although allowed in ANSI struct s rets return rets is invalid in SDCC although allowed in ANSI initialization of structure arrays must be fully braced struct s char x a 1 2 invalid in SDCC struct s char x a 1 2 OK long long 64 bit integers not supported double precision floating point not supported e No support for setjmp and longjmp for now e Old K amp R style function declarations are NOT allowed foo i j this old style of function declarations int i j are valid in ANSI but not valid in SDCC 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 _asm en dasm and naked Compliant eguivalents of these keywords are always available in a form that begin wi
111. ns 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 in sequence of execution dumpgcse Will create a dump of iCode s after global subexpression elimination into a file named lt source filename gt dumpgcse dumpdeadcode Will create a dump of iCode s after deadcode elimination into a file named lt source file name gt dumpdeadcode dumploop Will create a dump of iCode s after loop optimizations into a file named lt source file name gt dumploop dumprange Will create a dump of iCode s after live range analysis into a file named lt source file name gt dumprange dumlrange Will dump the life ranges for all symbols dumpregassign Will create a dump of iCode s 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 10 Redirecting output on Windows Shells By default SDCC writes it
112. nstant propagation 8 1 7 switch Statements 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 e The labels need not be in order and the starting number need not be one or zero the case labels are in numerical sequence or not too many case labels are missing switch i switch i case 4 case 0 case 5 case 1 case 3 case 6 case 3 case 7 case 4 72 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA case 8 case 5 case 9 case 6 case 10 case 7 case 11 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 swi
113. nt gt gt 8 OxFF will still be recognized 76 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 compiled 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 l a mov a l by 4 mov 1 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 seguence 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 ajmp and acall The following two rules will change all 1jmp and 1call to ajmp and acall replace lcall 1 by acall l replace ljmp 1 by ajmp 1 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 usi
114. nt 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 now should name all the modules rel files For an example see the standard library file libsdcc lib in the directory lt installdir gt share lib small 3 1 4 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 sdeclib 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 sdec c divsint c sdec c divuint c sdec c modsint c sdec c moduint c sdec 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 20 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC sdcclib libint lib divsint rel sdcclib libint lib divuint rel sdcclib libint lib _modsint rel sdcclib libint lib moduint
115. o get not updated at all Excuses in the past might have referred to problems with live range analysis but as this was fixed a while ago the current problem is that another excuse has to be found Kidding aside we have to get better there On the other hand there are daily snapshots available at snap http sdcc sourceforge net snap php and you can always build the very last version hopefully with many bugs fixed and features added from the source code available at Source http sdcc sourceforge net snap php Source 7 7 Examples You ll find some small examples in the directory sdcc device examples More examples and libraries are available at The SDCC Open Knowledge Resource http sdccokr dl9sec de web site or at http www pjre com tech 8051 7 8 Quality control The compiler is passed through nightly compile and build checks The so called regression tests check that SDCC itself compiles flawlessly on several platforms and checks the quality of the code generated by SDCC by running the code through simulators There is a separate document test_suite pdf about this 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 mes51 if you don t want to run the 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 pic port uses a diffe
116. oc lt Value gt 31 xram loc lt Value gt 22 xram size lt Value gt 23 31 xstack 23 24 29 44 c compile only 25 dD 22 dM 22 dN 22 mavr 22 INDEX INDEX mds390 21 mds400 21 mgbz80 21 mhc08 21 mmcs51 21 mpic14 22 mpic16 22 mxa51 22 mz80 21 o lt path file gt 25 lt file gt no extension 19 lt file gt adb 19 61 lt file gt asm 19 lt file gt cdb 19 61 lt file gt dump 19 lt file gt ihx 19 lt file gt lib 20 lt file gt Ink 20 lt file gt 1st 19 32 lt file gt map 19 31 32 lt file gt mem 19 31 lt file gt o 19 lt file gt rel 19 20 lt file gt rst 19 32 lt file gt sym 19 lt stdio h gt 44 defines 47 pragma callee_saves 25 45 pragma codeseg 46 pragma constseg 46 pragma disable_warning 45 pragma exclude 40 45 pragma less_pedantic 45 pragma nogcse 24 45 46 pragma noinduction 24 45 46 71 pragma noinvariant 24 45 pragma noiv 46 pragma nojtbound 24 46 74 pragma noloopreverse 46 pragma nooverlay 34 35 46 pragma opt_code_balanced 46 pragma opt_code_size 46 pragma opt_code_speed 46 pragma portmode 31 pragma preproc_asm 46 pragma restore 45 46 pragma save 45 46 pragma stackauto 33 46 pragma std_c89 46 pragma std_c99 46 pragma std_sdcc89 46 pragma std_sdcc99 46 _XPAGE mcs51 48 __ prefix for extended keywords 79 __asm 38 40 _
117. ode 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 preference 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 for lt 0 2 i 07 i f de k tl changed to itemp k 1 for i 0 i lt 100 i 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 1 lt 100 i ar i 5 1 3 changed to 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA itempl 0 itemp2 0 for i 0 1 lt 100 1 ar itempl itemp2 itempl 5 itemp2
118. ode for each file into different code pages and the compiler can allocate reusable variables more efficiently and there s less page selection overhead And as for any 8 bit micro especially for PIC 14 as they have a very simple instruction set use unsigned char whereever possible instead of int 4 5 2 Creating a device include file For generating a device include file use the support perl script inc2h pl kept in directory support script 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 is available from http sourceforge net projects gputils For linking you can use either GPUTIL s 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 Here is a Makefile using GPUTILS 49 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS sdcc S V mpicl4 pl6F877 lt gpasm c asm PRJ hex OBJS gplink m s PRJ 1kr o PRJ hex OBJS libsdcc lib Here is a Makefile using MPLAB JOW sdcc S V mpicl4 p16F877 lt mpasmwin q o asm
119. of time Users are advised to edit the device lib pic16 pics build file and then execute make lib io 4 6 9 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 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 7 contain no reference to pointers so they can be used with both memory models 4 6 10 Stack The stack implementation for the PIC16 port uses two indirect registers FSR1 and FSR2 FSR1 1s assigned as stack pointer FSR2 1s 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 55 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPOR
120. onversion The most common incompatibility resulting from this change is related to bit toggling idioms e g bit b b b equivalent to b 1 instead of toggling b b b toggles b In previous versions both forms would have toggled the bit lt pending more incompatibilities gt Obviously this has pros and cons 1 5 SYSTEM REQUIREMENTS CHAPTER 1 INTRODUCTION 1 5 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 The SDCC home page at http sdcc sourceforge net is a great place to find distribution sets You can also find links to the user mailing lists that offer help or discuss 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
121. or that source file and whose dependencies are all the files include d in it This rule may be a single line or may be continued with V 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 Wp preprocessorOption preprocessorOption Pass the preprocessorOption to the preprocessor sdcpp SDCC uses an adapted version of the p
122. pace 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 define a var in I O space at 78h called IoPort 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 If you include the file z180 h this will be set automatically 31 3 5 ABSOLUTE ADDRESSING CHAPTER 3 USING SDCC 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 efficien
123. processor does support an 8 8 bit multiplication 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 lr3 5 near int r2 recv Sample c 11 4 53 0 preHeaderLbl0 11 Sample c 11 5 55 0 iTemp6 1r5 16 4 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 lr7 8 int r2 r3 iTemp6 Ir5 16 _near int rO Sample c 11 8 8 1 if Temp4 lr7 8 int r2 13 0 goto whilebreak 0 3 Sample c 11 9 14 1 iTemp7 lr9 13 4 far int DPTR p 1r0 0 _far int Sample c 11 10 15 1 p Ir0 0 _far int p lr0 0 _far int 0x2 short Sample c 11 13 18 1 iTemp10 Ir13 14 int r2 13 E iTemp7 lr9 13 4 far int DPTR Sample c 11 14 19 1 Temp6 1r5 16 4 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 Temp2 lr18 40 short r2 0x0 short Sample c 13 19 23 0 Temp11 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
124. r 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 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 RI 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 81 9 1 THE ANATOMY OF THE COMPILER CHA
125. 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 r0 is allocated to both iTemp6 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 82 9 1 THE ANATOMY OF THE COMPILER CHAPTER 9 COMPILER INTERNALS which tells the back end that 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
126. rel sdcclib libint lib mulint rel If the file already exists in the library it will be replaced 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 __divsint_a 1 1 _ divsint PARM 2 divsint _divuint rel divuint a 1 1 divuint PARM 2 divuint reste 1 1 divuint count 1 1 divuint _modsint rel odsint_a_1_1 odsint_PARM_2 _ modsint _moduint rel oduint_a_1_1 oduint_PARM_2 oduint_count_1_1 oduint _mulint rel ulint_PARM_2 mulint If the source files are compiled using debug the corresponding debug information file adb will be include in the library file as well The library files created with sdeclib are plain text files so they can be viewed with a text editor It is not recomended to modify a library file created with sdeclib using a text editor as there are file indexes numbers located accross 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 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 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
127. rent set of regression tests you ll find them in the directory sdcc src regression Traffic on sdcc devel and sdcc user is about 100 mails month each not counting automated messages mid 2003 69 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 Elimination The compiler does local and global common subexpression elimination e g i xt yt i JE et 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 l 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 1 ine ary i 1 dead store global 1 dead store global 2 return global 3 unreachable will be changed to 70 8 1 OPTIMIZATIONS CHAPTER 8 SDCC TECHNICAL DATA int global void 1 global 2 8 1 3 Copy Propagation int f 4 nt a oj i 10 j lt i return j will be changed to int f 4 inte aoe Jy i 10 j 10 return 10 Note the dead stores created by this copy propagation will be eliminated by dead c
128. reprocessor cpp of the GNU Compiler Collection gcc if you need more dedicated options please refer to the documentation at http ww gnu org software gcc onlinedocs 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 22 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC 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 overlap any other memory areas su
129. rrupt 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 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 SIGHANDLERO but declares a naked function An example of using the macros above is shown below include lt picl8fregs h gt include lt signal h gt DEF_INTHIGH high_int DEF_HANDLER SIG_TMRO _tmr0_handler DEF_HANDLER SIG_BCOL _bcol_handler END_DEF 59 4 6 THE PICI6 PORT CHAPTER 4 NOTES ON SUPPORTED PROCESSORS SIGHANDLER _tmr0_handler 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
130. ry 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 30 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 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 11 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 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 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
131. s 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 C util and add these lines set BISON_SIMPLE C util bison simple set BISON_HAIRY C 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 sdec bin and you can compile using SDCC 2 4 7 Building SDCC Using Borland 1 From the sdcc directory run the command make f Makefile bcc This should regenerate all the exe files in the bin directory except for sdcdb exe which
132. s s pcoc eeaeee Pb eee Eee eA ee o k bi TA Geng Help us eg soe he ee SL a a a Se a a eo Ta COMIBBLOS s cos ARR ERR RA ee OR le te e SE Ba es LO Release PODES oi aa ee A ERG Bak Aa eA eS Ta LESS gt eye a he o oe Be ee ee ee ee eee b 7e Quality A IE ee eee 4 eA as 8 SDCC Technical Data Sl OMIMAN s e KARE RR ee eS ee a ES 8 1 1 Sub expression Elimination 8 1 2 Dead Code Elimination 81 3 Copy Propagation cese ee ee ce eres S14 Loop Optimiganons corra RE Ae eS 81 5 Lopp Reven un ee AR S16 Algebraic Simplifications 2 0 5 2 h25 56406 as 81 7 Switch SIEMENS 2005 y Re RS da Fees S18 Bitshiiting Operations 6 406645 ee DA Ee pa Bh RES SLE BIELSA sone coat FS be Ge OO ea eR Re SS 8 1 10 Nibble and Byte Swappingg 8 1 11 Highest Order Bit Any OrderBit 8 1 12 Higher Order Byte Higher Order Word 81 13 Peephole ODUMIZEL cios GO Ba ia a 82 ANSI Complianc occ i054 655844568 a a Pee ee dS S23 Cyclomatic Complexity eco iras bbe bet eee dees E es 4 Retargetting for other Processors gt s os ce RR ER cene 9 Compiler internals 9 1 The anatomy of the compiler lt 65 eee mas da etess 9 2 A few words about basic block successors predecessors and dominators 10 Acknowledgments Chapter 1 Introduction 1 1 About SDCC SDCC Small Device C Compiler is an open source retargettable optimizing ANSI C
133. s can also be loaded dynami cally while XEmacs is running set the environment variable EMACSLOADPATH 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 Current Listing j key binding Comment ni RARA AAA ri oon sdedb next from src SDCDB next command Ar e sdcdb back from src SDCDB back command O sdcdb cont from src SDCDB continue command it 8 sdcdb step from src SDCDB step command eee sdcdb whatis c sexp SDCDB ptypecommand for data at it buffer point ip ok sdcdbsrc delete SDCDB Delete all breakpoints if no arg ae given or delete arg C u arg x ppm sdcdbsrc frame SDCDB Display current frame if no arg Ki given or display frame arg si buffer point pivi sdedbsrc goto sdedb Goto the SDCDB output buffer REJO sdcdb print c sexp SDCDB print command for data at a buffer point IO sdcdbsrc goto sdcdb Goto the SDCDB output buffer SEME sdcdbsrc mode Toggles Sdedbsrc mode turns i
134. s 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 installs 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 27 3 4 STORAGE CLASS LANGUAGE EXTENSIONS CHAPTER 3 USING SDCC 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 solely used for debugging purposes They can change or disappear very quickly and will never be documented 3 4 Storage Class Language Extensions 3 4 1 MCS51 D8390 Storage Class Language Extensions In addition to the
135. s 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 26 3 3 ENVIRONMENT VARIABLES CHAPTER 3 USING SDCC more pedantic Actually this is not a SDCC compiler option but if you want more warnings you can use a separate tool dedicated to syntax 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 extended keywords like __at Oxab and __ interrupt 2 Splint has an excellent on line manual at http www splint org manual and it s capabilities 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 3 2 9 Intermediate Dump Options The following options are provided for the purpose of retargetting and debugging the compiler They provide a mea
136. s 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 61 5 5 DEBUGGER COMMANDS CHAPTER 5 DEBUGGING WITH SDCDB 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 e cd lt directory gt change to the lt directory gt e fullname used by GUI front ends e cpu lt cpu type gt this argument is passed to the simulator please see the simulator docs for details e X lt Clock frequency gt this options is passed to the simulator please see the simulator docs for details e s lt serial port file gt passed to simulator see the simulator docs for details e S lt serial in out gt passed to simulator see the simulator docs for details e k lt port number gt passed to simulator see the simulator docs for details 5 5 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 existing 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
137. stall Trouble ADOBE na 56 She eee 28 1 Iti SDCC does not build corectly o cs esu eree Bebe ee ee ee Bs 232 Whatithe Jeong does a poe BRS ER ER AE Back le ke bs 2 8 3 Whatthe make doods lt lt lt ooo 50644808 b ra wee wR Eee ee 2 8 4 What the make install commanddoes 29 ComponenisorSDCe fc ce esa abe ee eee eee eee we Re ewe ee ee eS 2 ld ee ots s e Ace Rhee et Ge RO Poe on we Be Oh aed hte Boe A 29 2 siepp The t Preprocessor Ls cirios ee RR ERR PR RR 2 9 3 asxxxx aslink link xxx The Assemblers and Linkage Editors 204 631 The SIMMO ss o a e NE ee RES Re ee E ee ok 208 dedb Source Level Deougser ocios Soe ee be PRE a ES pra se teva a 8 3 Using SDCC Sol A e EES we de ba we eee ES a ee gole Ka She od 3 1 1 Single Source File Projects cos cce s eest ee eRe ee ee EES 3 1 2 Projects with Multiple Source Files scc sona kw Be ee BSR Se Shee way S 33 Projects with Additional LIBTADES sic eb Eee a poe ee ee 3 1 4 Using sdcclib to Create and Manage Libraries 32 Command Line OPHOBES a g e z A AR e eee A A ADO Qu Un 10 10 11 11 12 12 12 13 14 14 14 15 15 15 16 16 16 16 16 17 17 17 17 18 CONTENTS CONTENTS 3 3 3 4 af 3 10 311 3 14 SL Head Procesor Selection OPUODS s o s sna 45 a a Ge a Sk eS 21 32 2 Preprocessor Opens oo 5054 40644 bbe e eee eee dee ee eee 22 323 ld IR 22 3 24 MCSSLOpiens osos a ee ee ee ee
138. t The port to the 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 4 5 The PIC14 port The 14bit PIC port still requires a major effort from the development community However it can work for very simple code 4 5 1 C code and 14bit PIC code page and RAM 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 treats all functions of a single C file as being in the same code page unless it is non static The compiler treats all local variables of a single C file as being in the same RAM bank unless it is an extern To get the best follow these guide lines 1 make local functions static as non static functions require code page selection overhead 2 Make local variables static as extern variables require RAM bank selection overhead 3 For devices that have multiple code pages it is more efficient to use the same number of files as pages i e for the 16F877 use 4 separate files and i e for the 16F874 use 2 separate files This way the linker can put the c
139. t assemble 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 25 3 2 COMMAND LINE OPTIONS CHAPTER 3 USING SDCC 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 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 might result in slightly smaller code and save two bytes of stack space The return from the main function will return to the function calling main The default setting gt is to lock up i e generate a 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
140. t 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 3 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 0x7ffe and 0x7fff 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 Variables with an absolute address are not initialized 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 12 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 sp
141. t off ri el o Cat sdcdb finish from src SDCDB finish command ri Py EX SPC sdcdb break Set break for line with point SO E sdcdbsrc mode Toggle Sdedbsrc mode 7 ESC m sdcdbsrc sremode Toggle list mode rr 64 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 int Oxfe int Oxfc04 1024 Another one unsigned char 12 signed char 3 lt No the result is not 4 int unsigned char 12 int signed char 3 int unsigned char 0xf4 int signed char Oxfd int 0x00f4 int Oxfffd int 0x00f4 int Oxfffd int 244 int 3 lt int 81 int Oxffaf Don t complain that gcc gives you a different result gcc uses 32 bit ints while SDCC us
142. tch 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 H switch case case case case case case case YHOO B WN Fo and switch i case 101 case 102 case 103 case 104 case 105 case 106 case 107 73 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 alr E rrc a mov iya 8 1 9 Bit rotation A special case of the bit shift operation is bit rotation SDCC recognizes th
143. termediate dump 27 Options linker 22 Options MCS51 23 Options optimization 24 Options other 25 Options PIC16 51 Options preprocessor 22 Options processor selection 21 Options SDCC configuration 8 Options Z80 24 Overlaying 34 P2 mcs51 sfr 29 45 48 Parameter passing 41 Parameters 33 Parsing 81 Patch submission 68 69 pdata mcs51 ds390 storage class 29 44 48 PDF version of this document 15 Peephole optimizer 25 39 77 PIC14 22 49 PIC16 22 50 53 54 57 66 Pointer 30 Pragmas 45 Preprocessor options 22 printf 44 printf fast mces51 44 printf fast f mcs51 44 printf small 44 printf tiny mcs51 44 Processor selection options 21 push pop 39 40 45 putchar 44 Ouality control 69 RAM bank pic14 49 reentrant 25 26 33 34 41 44 78 Register allocation 71 81 82 Register assignment 27 90 register bank mes51 ds390 31 33 37 Regression test 48 66 69 Related tools 67 Release policy 69 Reporting bugs 68 Reguesting features 7 68 return value 42 48 rotating bits 74 Runtime library 37 s51 17 18 sbit 6 SDCC 47 SDCC_ds390 47 SDCC_HOME 28 SDCC_INCLUDE 28 SDCC_LEAVE_SIGNALS 27 SDCC_LIB 28 SDCC_mes51 47 SDCC MODEL FLAT24 47 SDCC MODEL LARGE 47 SDCC MODEL MEDIUM 47 SDCC MODEL SMALL 47 SDCC STACK AUTO 47 SDCC STACK TENBIT 47 SDCC USE XSTACK 47 SDCC z80 47 sdeclib 20 21 sdcdb debugger 18 61
144. terrupt service routine is defined without using a register 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 8 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 11 for details on customizing startup 3 8 4 Z80 Interrupt Service Routines The Z80 uses several different methods for determining the correct interrupt vector depending on the hardware
145. th two underscores f e data instead of data 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 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 79 8 4 RETARGETTING FOR OTHER PROCESSORS CHAPTER 8 SDCC TECHNICAL DATA 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 iss
146. tion nooverlay the compiler will not overlay the parameters and local variables of a function stackauto See option stack auto and section 3 6 Parameters and Local Variables 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 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 constseg lt name gt Use this name max 8 characters for the const segment SDCPP supports the following pragma directives preproc_asm switch _asm endasm block preprocessing on off Default is on The pragma s are intended to be used to turn on or off certain optimizations which might cause the compiler to generat
147. ts 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 or large 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 When the small model is used variables without storage class are allocated in the internal ram 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 17 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 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 44 3 18 PRAGMAS CHAPTER 3 USING SDCC variables are allocated on the external stack note support libr
148. ttings to configure The other Win32 builds using Borland VC or whatever don t use configure but a header file sdec_vc_in h is the same as sdecconf h built by configure for Win32 These defaults are Variable default Win32 builds PREFIX usr local Usdec EXEC PREFIX PREFIX PREFIX BINDIR EXECPREFIXhbin EXECPREFIX bin DATADIR PREFIX share PREFIX DOCDIR DATADIR sdec doc DATADIR doc INCLUDE DIR SUFFIX sdec include include LIB DIR SUFFIX sdec lib 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 Z PREFIX2BIN DIR bin bin PREFIX2DATA DIR share sdcc Examples configure configure prefix usr bin datadir usr share configure disable avr port disable xa5l port To cross compile on linux for Mingw32 see also sdcc support scripts sdcc_mingw32 configure N CC i586 mingw32msvc gcc CXX 1586 mingw32msvc g A RANLIB 1586 mingw32msvc ranlib A STRIP i586 mingw32msvc strip A prefix sdcc A 2 2 INSTALL PATHS CHAPTER 2 INSTALLING SDCC datadir sdec docdir sdcc doc include_dir_suffix include lib_dir_suffix lib sdccconf_h_dir_separator A disable device lib build disa
149. tware 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 and new terms are printed in italic 1 4 Compatibility with previous versions This version has numerous bug fixes compared with the previous version But we also introduced some incompat ibilities 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 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 e g char a 3 printf Sd cin a char a will push a as an int and as a char resp e option regextend has been removed e option noregparms has been removed e option stack after data has been removed bit and sbit types now consistently behave like the C99 _Bool type with respect to type c
150. ues 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 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 optimizations like bit rotation etc 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 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 This phase determines the live ranges by live range I me
151. 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 its 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 The linker generates two files with memory allocation 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 s
152. w the instruction for Linux On OSX 2 x 1t was reported that the default gcc version 3 1 20020420 prerelease fails to compile 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 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 on Windows With the exception of Cygwin the SDCC binaries uCsim and sdcdb can t be built on Windows They use Unix sockets which are not available on Win32 2 4 5 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 sdec 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 g
153. y 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 amp 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 recognizes 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 hobl hob2 unsigned int howl how2 hobl gint gt gt 8 OxFF hob2 glong gt gt 24 howl glong gt gt 16 OxFFFF how2 glong gt gt 8 will generate the following code 91 hob we 15 0037 85 01 06 92 mov foo hobl 1 1 gint 1 93 hob c 16 003A 85 05 07 94 mov foo_hob2_1_1 _glong 3 95 hobre TT 003D 85 04 08 96 mov foo howl 1 1 glong 2 0040 85 05 09 97 mov foo howl 1 1 1 glong 3 0043 85 03 0A 98 mov foo how2 1 1 glong 1 0046 85 04 0B 99 mov foo how2 1 1 1 glong 2 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 gi

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