1 #LyX 1.2 created this file. For more info see http://www.lyx.org/
15 \use_numerical_citations 0
16 \paperorientation portrait
19 \paragraph_separation indent
21 \quotes_language swedish
29 Please note: double dashed longoptions (e.g.
30 --version) need three dashes in this document to be visable in html and
34 SDCC Compiler User Guide
38 \begin_inset LatexCommand \tableofcontents{}
55 is a Freeware, retargettable, optimizing ANSI-C compiler by
59 designed for 8 bit Microprocessors.
60 The current version targets Intel MCS51 based Microprocessors(8051,8052,
61 etc), Zilog Z80 based MCUs, and the Dallas DS80C390 variant.
62 It can be retargetted for other microprocessors, support for PIC, AVR and
63 186 is under development.
64 The entire source code for the compiler is distributed under GPL.
65 SDCC uses ASXXXX & ASLINK, a Freeware, retargettable assembler & linker.
66 SDCC has extensive language extensions suitable for utilizing various microcont
67 rollers and underlying hardware effectively.
72 In addition to the MCU specific optimizations SDCC also does a host of standard
76 global sub expression elimination,
79 loop optimizations (loop invariant, strength reduction of induction variables
83 constant folding & propagation,
99 For the back-end SDCC uses a global register allocation scheme which should
100 be well suited for other 8 bit MCUs.
105 The peep hole optimizer uses a rule based substitution mechanism which is
111 Supported data-types are:
114 char (8 bits, 1 byte),
117 short and int (16 bits, 2 bytes),
120 long (32 bit, 4 bytes)
127 The compiler also allows
129 inline assembler code
131 to be embedded anywhere in a function.
132 In addition, routines developed in assembly can also be called.
136 SDCC also provides an option (--cyclomatic) to report the relative complexity
138 These functions can then be further optimized, or hand coded in assembly
144 SDCC also comes with a companion source level debugger SDCDB, the debugger
145 currently uses ucSim a freeware simulator for 8051 and other micro-controllers.
150 The latest version can be downloaded from
151 \begin_inset LatexCommand \url{http://sdcc.sourceforge.net/}
163 All packages used in this compiler system are
171 ; source code for all the sub-packages (pre-processor, assemblers, linkers
172 etc) is distributed with the package.
173 This documentation is maintained using a freeware word processor (LyX).
175 This program is free software; you can redistribute it and/or modify it
176 under the terms of the GNU General Public License as published by the Free
177 Software Foundation; either version 2, or (at your option) any later version.
178 This program is distributed in the hope that it will be useful, but WITHOUT
179 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
180 FOR A PARTICULAR PURPOSE.
181 See the GNU General Public License for more details.
182 You should have received a copy of the GNU General Public License along
183 with this program; if not, write to the Free Software Foundation, 59 Temple
184 Place - Suite 330, Boston, MA 02111-1307, USA.
185 In other words, you are welcome to use, share and improve this program.
186 You are forbidden to forbid anyone else to use, share and improve what
188 Help stamp out software-hoarding!
191 Typographic conventions
194 Throughout this manual, we will use the following convention.
195 Commands you have to type in are printed in
203 Code samples are printed in
208 Interesting items and new terms are printed in
213 Compatibility with previous versions
216 This version has numerous bug fixes compared with the previous version.
217 But we also introduced some incompatibilities with older versions.
218 Not just for the fun of it, but to make the compiler more stable, efficient
225 short is now equivalent to int (16 bits), it used to be equivalent to char
226 (8 bits) which is not ANSI compliant
229 the default directory for gcc-builds where include, library and documention
230 files are stored is now in /usr/local/share
233 char type parameters to vararg functions are casted to int unless explicitly
250 will push a as an int and as a char resp.
253 option ---regextend has been removed
256 option ---noregparms has been removed
259 option ---stack-after-data has been removed
264 <pending: more incompatibilities?>
270 What do you need before you start installation of SDCC? A computer, and
272 The preferred method of installation is to compile SDCC from source using
274 For Windows some pre-compiled binary distributions are available for your
276 You should have some experience with command line tools and compiler use.
282 The SDCC home page at
283 \begin_inset LatexCommand \url{http://sdcc.sourceforge.net/}
287 is a great place to find distribution sets.
288 You can also find links to the user mailing lists that offer help or discuss
289 SDCC with other SDCC users.
290 Web links to other SDCC related sites can also be found here.
291 This document can be found in the DOC directory of the source package as
293 Some of the other tools (simulator and assembler) included with SDCC contain
294 their own documentation and can be found in the source distribution.
295 If you want the latest unreleased software, the complete source package
296 is available directly by anonymous CVS on cvs.sdcc.sourceforge.net.
299 Wishes for the future
302 There are (and always will be) some things that could be done.
303 Here are some I can think of:
310 char KernelFunction3(char p) at 0x340;
316 If you can think of some more, please send them to the list.
322 <pending: And then of course a proper index-table
323 \begin_inset LatexCommand \index{index}
333 Install and search paths
336 Linux (and other gcc-builds like Solaris, Cygwin, Mingw32 and OSX) by default
337 install in /usr/local.
338 You can override this when configuring with ---prefix-path.
339 Subdirs used will be bin, share/sdcc/include, share/sdcc/lib and share/sdcc/doc.
341 Windows MSVC and Borland builds will install in one single tree (e.g.
342 /sdcc) with subdirs bin, lib, include and doc.
346 The paths searched when running the compiler are as follows (the first catch
350 Binary files (preprocessor, assembler and linker):
352 - the path of argv[0] (if available)
355 \begin_inset Quotes sld
359 \begin_inset Quotes srd
365 \begin_inset Quotes sld
369 \begin_inset Quotes srd
382 \begin_inset Quotes sld
386 \begin_inset Quotes srd
392 \begin_inset Quotes sld
396 \begin_inset Quotes srd
401 - /usr/local/share/sdcc/include (gcc builds)
403 - path(arv[0])/../include and then /sdcc/include (as a last resort for windoze
404 msvc and borland builds)
411 is auto-appended by the compiler, e.g.
412 small, large, z80, ds390 etc.):
417 \begin_inset Quotes sld
421 \begin_inset Quotes srd
431 \begin_inset Quotes sld
435 \begin_inset Quotes srd
444 - /usr/local/share/sdcc/lib/
450 - path(argv[0])/../lib/
458 (as a last resort for windoze msvc and borland builds)
461 Documentation (although never really searched for, you have to do that yourself
465 \begin_inset Quotes sld
469 \begin_inset Quotes srd
474 - /usr/local/share/sdcc/doc (gcc builds)
476 - /sdcc/doc (windoze msvc and borland builds)
479 So, for windoze it is highly recommended to set the environment variable
480 SDCCHOME to prevent needless usage of -I and -L options.
481 For gcc-builds SDCCHOME should only be set when sdcc is installed in non-standa
485 Linux and other gcc-based systems (cygwin, mingw32, osx)
490 Download the source package
492 either from the SDCC CVS repository or from the
493 \begin_inset LatexCommand \url[nightly snapshots]{http://sdcc.sourceforge.net/snap.php}
499 , it will be named something like sdcc
508 Bring up a command line terminal, such as xterm.
513 Unpack the file using a command like:
516 "tar -xzf sdcc.src.tgz
521 , this will create a sub-directory called sdcc with all of the sources.
524 Change directory into the main SDCC directory, for example type:
541 This configures the package for compilation on your system.
557 All of the source packages will compile, this can take a while.
573 This copies the binary executables, the include files, the libraries and
574 the documentation to the install directories.
578 \layout Subsubsection
580 Windows Install Using a Binary Package
583 Download the binary package and unpack it using your favorite unpacking
584 tool (gunzip, WinZip, etc).
585 This should unpack to a group of sub-directories.
586 An example directory structure after unpacking the mingw32 package is:
593 bin for the executables, c:
613 lib for the include and libraries.
616 Adjust your environment variable PATH to include the location of the bin
617 directory or start sdcc using the full path.
618 \layout Subsubsection
620 Windows Install Using Cygwin and Mingw32
623 Follow the instruction in
625 Linux and other gcc-based systems
628 \layout Subsubsection
630 Windows Install Using Microsoft Visual C++ 6.0/NET
635 Download the source package
637 either from the SDCC CVS repository or from the
638 \begin_inset LatexCommand \url[nightly snapshots]{http://sdcc.sourceforge.net/snap.php}
644 , it will be named something like sdcc
651 SDCC is distributed with all the projects, workspaces, and files you need
652 to build it using Visual C++ 6.0/NET.
653 The workspace name is 'sdcc.dsw'.
654 Please note that as it is now, all the executables are created in a folder
658 Once built you need to copy the executables from sdcc
662 bin before runnng SDCC.
667 In order to build SDCC with Visual C++ 6.0/NET you need win32 executables
668 of bison.exe, flex.exe, and gawk.exe.
669 One good place to get them is
670 \begin_inset LatexCommand \url[here]{http://unxutils.sourceforge.net}
678 Download the file UnxUtils.zip.
679 Now you have to install the utilities and setup Visual C++ so it can locate
680 the required programs.
681 Here there are two alternatives (choose one!):
688 a) Extract UnxUtils.zip to your C:
690 hard disk PRESERVING the original paths, otherwise bison won't work.
691 (If you are using WinZip make certain that 'Use folder names' is selected)
695 b) In the Visual C++ IDE click Tools, Options, select the Directory tab,
696 in 'Show directories for:' select 'Executable files', and in the directories
697 window add a new path: 'C:
707 (As a side effect, you get a bunch of Unix utilities that could be useful,
708 such as diff and patch.)
715 This one avoids extracting a bunch of files you may not use, but requires
720 a) Create a directory were to put the tools needed, or use a directory already
728 b) Extract 'bison.exe', 'bison.hairy', 'bison.simple', 'flex.exe', and gawk.exe
729 to such directory WITHOUT preserving the original paths.
730 (If you are using WinZip make certain that 'Use folder names' is not selected)
734 c) Rename bison.exe to '_bison.exe'.
738 d) Create a batch file 'bison.bat' in 'C:
742 ' and add these lines:
762 _bison %1 %2 %3 %4 %5 %6 %7 %8 %9
766 Steps 'c' and 'd' are needed because bison requires by default that the
767 files 'bison.simple' and 'bison.hairy' reside in some weird Unix directory,
768 '/usr/local/share/' I think.
769 So it is necessary to tell bison where those files are located if they
770 are not in such directory.
771 That is the function of the environment variables BISON_SIMPLE and BISON_HAIRY.
775 e) In the Visual C++ IDE click Tools, Options, select the Directory tab,
776 in 'Show directories for:' select 'Executable files', and in the directories
777 window add a new path: 'c:
780 Note that you can use any other path instead of 'c:
782 util', even the path where the Visual C++ tools are, probably: 'C:
786 Microsoft Visual Studio
791 So you don't have to execute step 'e' :)
795 Open 'sdcc.dsw' in Visual Studio, click 'build all', when it finishes copy
796 the executables from sdcc
800 bin, and you can compile using sdcc.
801 \layout Subsubsection
803 Windows Install Using Borland
806 From the sdcc directory, run the command "make -f Makefile.bcc".
807 This should regenerate all the .exe files in the bin directory except for
808 sdcdb.exe (which currently doesn't build under Borland C++).
811 If you modify any source files and need to rebuild, be aware that the dependanci
812 es may not be correctly calculated.
813 The safest option is to delete all .obj files and run the build again.
814 From a Cygwin BASH prompt, this can easily be done with the commmand:
824 ( -name '*.obj' -o -name '*.lib' -o -name '*.rul'
835 or on Windows NT/2000/XP from the command prompt with the commmand:
842 del /s *.obj *.lib *.rul
845 from the sdcc directory.
848 Testing out the SDCC Compiler
851 The first thing you should do after installing your SDCC compiler is to
859 at the prompt, and the program should run and tell you the version.
860 If it doesn't run, or gives a message about not finding sdcc program, then
861 you need to check over your installation.
862 Make sure that the sdcc bin directory is in your executable search path
863 defined by the PATH environment setting (see the Trouble-shooting section
865 Make sure that the sdcc program is in the bin folder, if not perhaps something
866 did not install correctly.
874 is commonly installed as described in section
875 \begin_inset Quotes sld
878 Install and search paths
879 \begin_inset Quotes srd
888 Make sure the compiler works on a very simple example.
889 Type in the following test.c program using your favorite
924 Compile this using the following command:
933 If all goes well, the compiler will generate a test.asm and test.rel file.
934 Congratulations, you've just compiled your first program with SDCC.
935 We used the -c option to tell SDCC not to link the generated code, just
936 to keep things simple for this step.
944 The next step is to try it with the linker.
954 If all goes well the compiler will link with the libraries and produce
955 a test.ihx output file.
960 (no test.ihx, and the linker generates warnings), then the problem is most
961 likely that sdcc cannot find the
965 usr/local/share/sdcc/lib directory
969 (see the Install trouble-shooting section for suggestions).
977 The final test is to ensure sdcc can use the
981 header files and libraries.
982 Edit test.c and change it to the following:
1002 strcpy(str1, "testing");
1011 Compile this by typing
1018 This should generate a test.ihx output file, and it should give no warnings
1019 such as not finding the string.h file.
1020 If it cannot find the string.h file, then the problem is that sdcc cannot
1021 find the /usr/local/share/sdcc/include directory
1025 (see the Install trouble-shooting section for suggestions).
1028 Install Trouble-shooting
1029 \layout Subsubsection
1031 SDCC does not build correctly.
1034 A thing to try is starting from scratch by unpacking the .tgz source package
1035 again in an empty directory.
1043 ./configure 2>&1 | tee configure.log
1057 make 2>&1 | tee make.log
1064 If anything goes wrong, you can review the log files to locate the problem.
1065 Or a relevant part of this can be attached to an email that could be helpful
1066 when requesting help from the mailing list.
1067 \layout Subsubsection
1070 \begin_inset Quotes sld
1074 \begin_inset Quotes srd
1081 \begin_inset Quotes sld
1085 \begin_inset Quotes srd
1088 command is a script that analyzes your system and performs some configuration
1089 to ensure the source package compiles on your system.
1090 It will take a few minutes to run, and will compile a few tests to determine
1091 what compiler features are installed.
1092 \layout Subsubsection
1095 \begin_inset Quotes sld
1099 \begin_inset Quotes srd
1105 This runs the GNU make tool, which automatically compiles all the source
1106 packages into the final installed binary executables.
1107 \layout Subsubsection
1110 \begin_inset Quotes sld
1114 \begin_inset Quotes erd
1120 This will install the compiler, other executables libraries and include
1121 files in to the appropriate directories.
1123 \begin_inset Quotes sld
1126 Install and Search PATHS
1127 \begin_inset Quotes srd
1132 On most systems you will need super-user privilages to do this.
1138 SDCC is not just a compiler, but a collection of tools by various developers.
1139 These include linkers, assemblers, simulators and other components.
1140 Here is a summary of some of the components.
1141 Note that the included simulator and assembler have separate documentation
1142 which you can find in the source package in their respective directories.
1143 As SDCC grows to include support for other processors, other packages from
1144 various developers are included and may have their own sets of documentation.
1148 You might want to look at the files which are installed in <installdir>.
1149 At the time of this writing, we find the following programs for gcc-builds:
1153 In <installdir>/bin:
1156 sdcc - The compiler.
1159 sdcpp - The C preprocessor.
1162 asx8051 - The assembler for 8051 type processors.
1169 as-gbz80 - The Z80 and GameBoy Z80 assemblers.
1172 aslink -The linker for 8051 type processors.
1179 link-gbz80 - The Z80 and GameBoy Z80 linkers.
1182 s51 - The ucSim 8051 simulator.
1185 sdcdb - The source debugger.
1188 packihx - A tool to pack (compress) Intel hex files.
1191 In <installdir>/share/sdcc/include
1197 In <installdir>/share/sdcc/lib
1200 the subdirs src and small, large, z80, gbz80 and ds390 with the precompiled
1204 In <installdir>/share/sdcc/doc
1210 As development for other processors proceeds, this list will expand to include
1211 executables to support processors like AVR, PIC, etc.
1212 \layout Subsubsection
1217 This is the actual compiler, it in turn uses the c-preprocessor and invokes
1218 the assembler and linkage editor.
1219 \layout Subsubsection
1221 sdcpp - The C-Preprocessor
1224 The preprocessor is a modified version of the GNU preprocessor.
1225 The C preprocessor is used to pull in #include sources, process #ifdef
1226 statements, #defines and so on.
1227 \layout Subsubsection
1229 asx8051, as-z80, as-gbz80, aslink, link-z80, link-gbz80 - The Assemblers
1233 This is retargettable assembler & linkage editor, it was developed by Alan
1235 John Hartman created the version for 8051, and I (Sandeep) have made some
1236 enhancements and bug fixes for it to work properly with the SDCC.
1237 \layout Subsubsection
1242 S51 is a freeware, opensource simulator developed by Daniel Drotos (
1243 \begin_inset LatexCommand \url{mailto:drdani@mazsola.iit.uni-miskolc.hu}
1248 The simulator is built as part of the build process.
1249 For more information visit Daniel's website at:
1250 \begin_inset LatexCommand \url{http://mazsola.iit.uni-miskolc.hu/~drdani/embedded/s51}
1255 It currently support the core mcs51, the Dallas DS80C390 and the Philips
1257 \layout Subsubsection
1259 sdcdb - Source Level Debugger
1265 <todo: is this thing still alive?>
1272 Sdcdb is the companion source level debugger.
1273 The current version of the debugger uses Daniel's Simulator S51, but can
1274 be easily changed to use other simulators.
1281 \layout Subsubsection
1283 Single Source File Projects
1286 For single source file 8051 projects the process is very simple.
1287 Compile your programs with the following command
1290 "sdcc sourcefile.c".
1294 This will compile, assemble and link your source file.
1295 Output files are as follows
1299 sourcefile.asm - Assembler source file created by the compiler
1301 sourcefile.lst - Assembler listing file created by the Assembler
1303 sourcefile.rst - Assembler listing file updated with linkedit information,
1304 created by linkage editor
1306 sourcefile.sym - symbol listing for the sourcefile, created by the assembler
1308 sourcefile.rel - Object file created by the assembler, input to Linkage editor
1310 sourcefile.map - The memory map for the load module, created by the Linker
1312 sourcefile.ihx - The load module in Intel hex format (you can select the
1313 Motorola S19 format with ---out-fmt-s19)
1315 sourcefile.cdb - An optional file (with ---debug) containing debug information
1317 sourcefile.dump* - Dump file to debug the compiler it self (with ---dumpall)
1319 \begin_inset Quotes sld
1322 Anatomy of the compiler
1323 \begin_inset Quotes srd
1327 \layout Subsubsection
1329 Projects with Multiple Source Files
1332 SDCC can compile only ONE file at a time.
1333 Let us for example assume that you have a project containing the following
1338 foo1.c (contains some functions)
1340 foo2.c (contains some more functions)
1342 foomain.c (contains more functions and the function main)
1350 The first two files will need to be compiled separately with the commands:
1382 Then compile the source file containing the
1386 function and link the files together with the following command:
1394 foomain.c\SpecialChar ~
1395 foo1.rel\SpecialChar ~
1407 can be separately compiled as well:
1418 sdcc foomain.rel foo1.rel foo2.rel
1425 The file containing the
1440 file specified in the command line, since the linkage editor processes
1441 file in the order they are presented to it.
1442 \layout Subsubsection
1444 Projects with Additional Libraries
1447 Some reusable routines may be compiled into a library, see the documentation
1448 for the assembler and linkage editor (which are in <installdir>/share/sdcc/doc)
1454 Libraries created in this manner can be included in the command line.
1455 Make sure you include the -L <library-path> option to tell the linker where
1456 to look for these files if they are not in the current directory.
1457 Here is an example, assuming you have the source file
1469 (if that is not the same as your current project):
1476 sdcc foomain.c foolib.lib -L mylib
1487 must be an absolute path name.
1491 The most efficient way to use libraries is to keep seperate modules in seperate
1493 The lib file now should name all the modules.rel files.
1494 For an example see the standard library file
1498 in the directory <installdir>/share/lib/small.
1501 Command Line Options
1502 \layout Subsubsection
1504 Processor Selection Options
1506 \labelwidthstring 00.00.0000
1512 Generate code for the MCS51 (8051) family of processors.
1513 This is the default processor target.
1515 \labelwidthstring 00.00.0000
1521 Generate code for the DS80C390 processor.
1523 \labelwidthstring 00.00.0000
1529 Generate code for the Z80 family of processors.
1531 \labelwidthstring 00.00.0000
1537 Generate code for the GameBoy Z80 processor.
1539 \labelwidthstring 00.00.0000
1545 Generate code for the Atmel AVR processor (In development, not complete).
1547 \labelwidthstring 00.00.0000
1553 Generate code for the PIC 14-bit processors (In development, not complete).
1555 \labelwidthstring 00.00.0000
1561 Generate code for the Toshiba TLCS-900H processor (In development, not
1564 \labelwidthstring 00.00.0000
1570 Generate code for the Philips XA51 processor (In development, not complete).
1571 \layout Subsubsection
1573 Preprocessor Options
1575 \labelwidthstring 00.00.0000
1581 The additional location where the pre processor will look for <..h> or
1582 \begin_inset Quotes eld
1586 \begin_inset Quotes erd
1591 \labelwidthstring 00.00.0000
1597 Command line definition of macros.
1598 Passed to the pre processor.
1600 \labelwidthstring 00.00.0000
1606 Tell the preprocessor to output a rule suitable for make describing the
1607 dependencies of each object file.
1608 For each source file, the preprocessor outputs one make-rule whose target
1609 is the object file name for that source file and whose dependencies are
1610 all the files `#include'd in it.
1611 This rule may be a single line or may be continued with `
1613 '-newline if it is long.
1614 The list of rules is printed on standard output instead of the preprocessed
1618 \labelwidthstring 00.00.0000
1624 Tell the preprocessor not to discard comments.
1625 Used with the `-E' option.
1627 \labelwidthstring 00.00.0000
1638 Like `-M' but the output mentions only the user header files included with
1640 \begin_inset Quotes eld
1644 System header files included with `#include <file>' are omitted.
1646 \labelwidthstring 00.00.0000
1652 Assert the answer answer for question, in case it is tested with a preprocessor
1653 conditional such as `#if #question(answer)'.
1654 `-A-' disables the standard assertions that normally describe the target
1657 \labelwidthstring 00.00.0000
1663 (answer) Assert the answer answer for question, in case it is tested with
1664 a preprocessor conditional such as `#if #question(answer)'.
1665 `-A-' disables the standard assertions that normally describe the target
1668 \labelwidthstring 00.00.0000
1674 Undefine macro macro.
1675 `-U' options are evaluated after all `-D' options, but before any `-include'
1676 and `-imacros' options.
1678 \labelwidthstring 00.00.0000
1684 Tell the preprocessor to output only a list of the macro definitions that
1685 are in effect at the end of preprocessing.
1686 Used with the `-E' option.
1688 \labelwidthstring 00.00.0000
1694 Tell the preprocessor to pass all macro definitions into the output, in
1695 their proper sequence in the rest of the output.
1697 \labelwidthstring 00.00.0000
1708 Like `-dD' except that the macro arguments and contents are omitted.
1709 Only `#define name' is included in the output.
1710 \layout Subsubsection
1714 \labelwidthstring 00.00.0000
1724 <absolute path to additional libraries> This option is passed to the linkage
1725 editor's additional libraries search path.
1726 The path name must be absolute.
1727 Additional library files may be specified in the command line.
1728 See section Compiling programs for more details.
1730 \labelwidthstring 00.00.0000
1736 <Value> The start location of the external ram, default value is 0.
1737 The value entered can be in Hexadecimal or Decimal format, e.g.: ---xram-loc
1738 0x8000 or ---xram-loc 32768.
1740 \labelwidthstring 00.00.0000
1746 <Value> The start location of the code segment, default value 0.
1747 Note when this option is used the interrupt vector table is also relocated
1748 to the given address.
1749 The value entered can be in Hexadecimal or Decimal format, e.g.: ---code-loc
1750 0x8000 or ---code-loc 32768.
1752 \labelwidthstring 00.00.0000
1758 <Value> By default the stack is placed after the data segment.
1759 Using this option the stack can be placed anywhere in the internal memory
1761 The value entered can be in Hexadecimal or Decimal format, e.g.
1762 ---stack-loc 0x20 or ---stack-loc 32.
1763 Since the sp register is incremented before a push or call, the initial
1764 sp will be set to one byte prior the provided value.
1765 The provided value should not overlap any other memory areas such as used
1766 register banks or the data segment and with enough space for the current
1769 \labelwidthstring 00.00.0000
1775 <Value> The start location of the internal ram data segment.
1776 The value entered can be in Hexadecimal or Decimal format, eg.
1777 ---data-loc 0x20 or ---data-loc 32.
1778 (By default, the start location of the internal ram data segment is set
1779 as low as possible in memory, taking into account the used register banks
1780 and the bit segment at address 0x20.
1781 For example if register banks 0 and 1 are used without bit variables, the
1782 data segment will be set, if ---data-loc is not used, to location 0x10.)
1784 \labelwidthstring 00.00.0000
1790 <Value> The start location of the indirectly addressable internal ram, default
1792 The value entered can be in Hexadecimal or Decimal format, eg.
1793 ---idata-loc 0x88 or ---idata-loc 136.
1795 \labelwidthstring 00.00.0000
1804 The linker output (final object code) is in Intel Hex format.
1805 (This is the default option).
1807 \labelwidthstring 00.00.0000
1816 The linker output (final object code) is in Motorola S19 format.
1817 \layout Subsubsection
1821 \labelwidthstring 00.00.0000
1827 Generate code for Large model programs see section Memory Models for more
1829 If this option is used all source files in the project should be compiled
1831 In addition the standard library routines are compiled with small model,
1832 they will need to be recompiled.
1834 \labelwidthstring 00.00.0000
1845 Generate code for Small Model programs see section Memory Models for more
1847 This is the default model.
1848 \layout Subsubsection
1852 \labelwidthstring 00.00.0000
1863 Generate 24-bit flat mode code.
1864 This is the one and only that the ds390 code generator supports right now
1865 and is default when using
1870 See section Memory Models for more details.
1872 \labelwidthstring 00.00.0000
1878 Generate code for the 10 bit stack mode of the Dallas DS80C390 part.
1879 This is the one and only that the ds390 code generator supports right now
1880 and is default when using
1885 In this mode, the stack is located in the lower 1K of the internal RAM,
1886 which is mapped to 0x400000.
1887 Note that the support is incomplete, since it still uses a single byte
1888 as the stack pointer.
1889 This means that only the lower 256 bytes of the potential 1K stack space
1890 will actually be used.
1891 However, this does allow you to reclaim the precious 256 bytes of low RAM
1892 for use for the DATA and IDATA segments.
1893 The compiler will not generate any code to put the processor into 10 bit
1895 It is important to ensure that the processor is in this mode before calling
1896 any re-entrant functions compiled with this option.
1897 In principle, this should work with the
1901 option, but that has not been tested.
1902 It is incompatible with the
1907 It also only makes sense if the processor is in 24 bit contiguous addressing
1910 ---model-flat24 option
1913 \layout Subsubsection
1915 Optimization Options
1917 \labelwidthstring 00.00.0000
1923 Will not do global subexpression elimination, this option may be used when
1924 the compiler creates undesirably large stack/data spaces to store compiler
1926 A warning message will be generated when this happens and the compiler
1927 will indicate the number of extra bytes it allocated.
1928 It recommended that this option NOT be used, #pragma\SpecialChar ~
1930 to turn off global subexpression elimination for a given function only.
1932 \labelwidthstring 00.00.0000
1938 Will not do loop invariant optimizations, this may be turned off for reasons
1939 explained for the previous option.
1940 For more details of loop optimizations performed see section Loop Invariants.It
1941 recommended that this option NOT be used, #pragma\SpecialChar ~
1942 NOINVARIANT can be used
1943 to turn off invariant optimizations for a given function only.
1945 \labelwidthstring 00.00.0000
1951 Will not do loop induction optimizations, see section strength reduction
1952 for more details.It is recommended that this option is NOT used, #pragma\SpecialChar ~
1954 ION can be used to turn off induction optimizations for a given function
1957 \labelwidthstring 00.00.0000
1968 Will not generate boundary condition check when switch statements are implement
1969 ed using jump-tables.
1970 See section Switch Statements for more details.
1971 It is recommended that this option is NOT used, #pragma\SpecialChar ~
1973 used to turn off boundary checking for jump tables for a given function
1976 \labelwidthstring 00.00.0000
1985 Will not do loop reversal optimization.
1987 \labelwidthstring 00.00.0000
1993 This will disable the memcpy of initialized data in far space from code
1995 \layout Subsubsection
1999 \labelwidthstring 00.00.0000
2006 will compile and assemble the source, but will not call the linkage editor.
2008 \labelwidthstring 00.00.0000
2014 Run only the C preprocessor.
2015 Preprocess all the C source files specified and output the results to standard
2018 \labelwidthstring 00.00.0000
2025 The output path resp.
2026 file where everything will be placed.
2027 If the parameter is a path, it must have a trailing slash (or backslash
2028 for the Windows binaries) to be recognized as a path.
2031 \labelwidthstring 00.00.0000
2042 All functions in the source file will be compiled as
2047 the parameters and local variables will be allocated on the stack.
2048 see section Parameters and Local Variables for more details.
2049 If this option is used all source files in the project should be compiled
2053 \labelwidthstring 00.00.0000
2059 Uses a pseudo stack in the first 256 bytes in the external ram for allocating
2060 variables and passing parameters.
2061 See section on external stack for more details.
2063 \labelwidthstring 00.00.0000
2067 ---callee-saves function1[,function2][,function3]....
2070 The compiler by default uses a caller saves convention for register saving
2071 across function calls, however this can cause unneccessary register pushing
2072 & popping when calling small functions from larger functions.
2073 This option can be used to switch the register saving convention for the
2074 function names specified.
2075 The compiler will not save registers when calling these functions, no extra
2076 code will be generated at the entry & exit for these functions to save
2077 & restore the registers used by these functions, this can SUBSTANTIALLY
2078 reduce code & improve run time performance of the generated code.
2079 In the future the compiler (with interprocedural analysis) will be able
2080 to determine the appropriate scheme to use for each function call.
2081 DO NOT use this option for built-in functions such as _muluint..., if this
2082 option is used for a library function the appropriate library function
2083 needs to be recompiled with the same option.
2084 If the project consists of multiple source files then all the source file
2085 should be compiled with the same ---callee-saves option string.
2086 Also see #pragma\SpecialChar ~
2089 \labelwidthstring 00.00.0000
2098 When this option is used the compiler will generate debug information, that
2099 can be used with the SDCDB.
2100 The debug information is collected in a file with .cdb extension.
2101 For more information see documentation for SDCDB.
2103 \labelwidthstring 00.00.0000
2109 <filename> This option can be used to use additional rules to be used by
2110 the peep hole optimizer.
2111 See section Peep Hole optimizations for details on how to write these rules.
2113 \labelwidthstring 00.00.0000
2124 Stop after the stage of compilation proper; do not assemble.
2125 The output is an assembler code file for the input file specified.
2127 \labelwidthstring 00.00.0000
2131 -Wa_asmOption[,asmOption]
2134 Pass the asmOption to the assembler.
2136 \labelwidthstring 00.00.0000
2140 -Wl_linkOption[,linkOption]
2143 Pass the linkOption to the linker.
2145 \labelwidthstring 00.00.0000
2154 Integer (16 bit) and long (32 bit) libraries have been compiled as reentrant.
2155 Note by default these libraries are compiled as non-reentrant.
2156 See section Installation for more details.
2158 \labelwidthstring 00.00.0000
2167 This option will cause the compiler to generate an information message for
2168 each function in the source file.
2169 The message contains some
2173 information about the function.
2174 The number of edges and nodes the compiler detected in the control flow
2175 graph of the function, and most importantly the
2177 cyclomatic complexity
2179 see section on Cyclomatic Complexity for more details.
2181 \labelwidthstring 00.00.0000
2190 Floating point library is compiled as reentrant.See section Installation
2193 \labelwidthstring 00.00.0000
2199 The compiler will not overlay parameters and local variables of any function,
2200 see section Parameters and local variables for more details.
2202 \labelwidthstring 00.00.0000
2208 This option can be used when the code generated is called by a monitor
2210 The compiler will generate a 'ret' upon return from the 'main' function.
2211 The default option is to lock up i.e.
2214 \labelwidthstring 00.00.0000
2220 Disable peep-hole optimization.
2222 \labelwidthstring 00.00.0000
2228 Pass the inline assembler code through the peep hole optimizer.
2229 This can cause unexpected changes to inline assembler code, please go through
2230 the peephole optimizer rules defined in the source file tree '<target>/peeph.def
2231 ' before using this option.
2233 \labelwidthstring 00.00.0000
2239 <Value> Causes the linker to check if the internal ram usage is within limits
2242 \labelwidthstring 00.00.0000
2248 <Value> Causes the linker to check if the external ram usage is within limits
2251 \labelwidthstring 00.00.0000
2257 <Value> Causes the linker to check if the code usage is within limits of
2260 \labelwidthstring 00.00.0000
2266 This will prevent the compiler from passing on the default include path
2267 to the preprocessor.
2269 \labelwidthstring 00.00.0000
2275 This will prevent the compiler from passing on the default library path
2278 \labelwidthstring 00.00.0000
2284 Shows the various actions the compiler is performing.
2286 \labelwidthstring 00.00.0000
2292 Shows the actual commands the compiler is executing.
2294 \labelwidthstring 00.00.0000
2300 Hides your ugly and inefficient c-code from the asm file, so you can always
2301 blame the compiler :).
2303 \labelwidthstring 00.00.0000
2309 Include i-codes in the asm file.
2310 Looks like noise but is most helpfull for debugging the compiler itself.
2311 \layout Subsubsection
2313 Intermediate Dump Options
2316 The following options are provided for the purpose of retargetting and debugging
2318 These provided a means to dump the intermediate code (iCode) generated
2319 by the compiler in human readable form at various stages of the compilation
2323 \labelwidthstring 00.00.0000
2329 This option will cause the compiler to dump the intermediate code into
2332 <source filename>.dumpraw
2334 just after the intermediate code has been generated for a function, i.e.
2335 before any optimizations are done.
2336 The basic blocks at this stage ordered in the depth first number, so they
2337 may not be in sequence of execution.
2339 \labelwidthstring 00.00.0000
2345 Will create a dump of iCode's, after global subexpression elimination,
2348 <source filename>.dumpgcse.
2350 \labelwidthstring 00.00.0000
2356 Will create a dump of iCode's, after deadcode elimination, into a file
2359 <source filename>.dumpdeadcode.
2361 \labelwidthstring 00.00.0000
2370 Will create a dump of iCode's, after loop optimizations, into a file named
2373 <source filename>.dumploop.
2375 \labelwidthstring 00.00.0000
2384 Will create a dump of iCode's, after live range analysis, into a file named
2387 <source filename>.dumprange.
2389 \labelwidthstring 00.00.0000
2395 Will dump the life ranges for all symbols.
2397 \labelwidthstring 00.00.0000
2406 Will create a dump of iCode's, after register assignment, into a file named
2409 <source filename>.dumprassgn.
2411 \labelwidthstring 00.00.0000
2417 Will create a dump of the live ranges of iTemp's
2419 \labelwidthstring 00.00.0000
2430 Will cause all the above mentioned dumps to be created.
2433 Environment variables
2436 SDCC recognizes the following environment variables:
2438 \labelwidthstring 00.00.0000
2444 SDCC installs a signal handler to be able to delete temporary files after
2445 an user break (^C) or an exception.
2446 If this environment variable is set, SDCC won't install the signal handler
2447 in order to be able to debug SDCC.
2449 \labelwidthstring 00.00.0000
2457 Path, where temporary files will be created.
2458 The order of the variables is the search order.
2459 In a standard *nix environment these variables are not set, and there's
2460 no need to set them.
2461 On Windows it's recommended to set one of them.
2463 \labelwidthstring 00.00.0000
2467 (coming\SpecialChar ~
2472 \begin_inset Quotes sld
2475 2.1 Install and search paths
2476 \begin_inset Quotes srd
2481 \labelwidthstring 00.00.0000
2485 (coming\SpecialChar ~
2490 \begin_inset Quotes sld
2493 2.1 Install and search paths
2494 \begin_inset Quotes srd
2499 \labelwidthstring 00.00.0000
2503 (coming\SpecialChar ~
2508 \begin_inset Quotes sld
2511 2.1 Install and search paths
2512 \begin_inset Quotes srd
2517 \labelwidthstring 00.00.0000
2521 SDCCDIR\SpecialChar ~
2523 replaced\SpecialChar ~
2528 \begin_inset Quotes sld
2531 2.1 Install and search paths
2532 \begin_inset Quotes srd
2538 There are some more environment variables recognized by SDCC, but these
2539 are solely used for debugging purposes.
2540 They can change or disappear very quickly, and will never be documentated.
2543 MCS51/DS390 Storage Class Language Extensions
2546 In addition to the ANSI storage classes SDCC allows the following MCS51
2547 specific storage classes.
2548 \layout Subsubsection
2553 Variables declared with this storage class will be placed in the extern
2559 storage class for Large Memory model, e.g.:
2565 xdata unsigned char xduc;
2566 \layout Subsubsection
2575 storage class for Small Memory model.
2576 Variables declared with this storage class will be allocated in the internal
2584 \layout Subsubsection
2589 Variables declared with this storage class will be allocated into the indirectly
2590 addressable portion of the internal ram of a 8051, e.g.:
2597 \layout Subsubsection
2602 This is a data-type and a storage class specifier.
2603 When a variable is declared as a bit, it is allocated into the bit addressable
2604 memory of 8051, e.g.:
2611 \layout Subsubsection
2616 Like the bit keyword,
2620 signifies both a data-type and storage class, they are used to describe
2621 the special function registers and special bit variables of a 8051, eg:
2627 sfr at 0x80 P0; /* special function register P0 at location 0x80 */
2629 sbit at 0xd7 CY; /* CY (Carry Flag) */
2635 SDCC allows (via language extensions) pointers to explicitly point to any
2636 of the memory spaces of the 8051.
2637 In addition to the explicit pointers, the compiler uses (by default) generic
2638 pointers which can be used to point to any of the memory spaces.
2642 Pointer declaration examples:
2651 /* pointer physically in xternal ram pointing to object in internal ram
2654 data unsigned char * xdata p;
2658 /* pointer physically in code rom pointing to data in xdata space */
2660 xdata unsigned char * code p;
2664 /* pointer physically in code space pointing to data in code space */
2666 code unsigned char * code p;
2670 /* the folowing is a generic pointer physically located in xdata space */
2681 Well you get the idea.
2686 All unqualified pointers are treated as 3-byte (4-byte for the ds390)
2699 The highest order byte of the
2703 pointers contains the data space information.
2704 Assembler support routines are called whenever data is stored or retrieved
2710 These are useful for developing reusable library routines.
2711 Explicitly specifying the pointer type will generate the most efficient
2715 Parameters & Local Variables
2718 Automatic (local) variables and parameters to functions can either be placed
2719 on the stack or in data-space.
2720 The default action of the compiler is to place these variables in the internal
2721 RAM (for small model) or external RAM (for large model).
2722 This in fact makes them
2726 so by default functions are non-reentrant.
2730 They can be placed on the stack either by using the
2734 option or by using the
2738 keyword in the function declaration, e.g.:
2747 unsigned char foo(char i) reentrant
2760 Since stack space on 8051 is limited, the
2768 option should be used sparingly.
2769 Note that the reentrant keyword just means that the parameters & local
2770 variables will be allocated to the stack, it
2774 mean that the function is register bank independent.
2778 Local variables can be assigned storage classes and absolute addresses,
2785 unsigned char foo() {
2791 xdata unsigned char i;
2803 data at 0x31 unsiged char j;
2818 In the above example the variable
2822 will be allocated in the external ram,
2826 in bit addressable space and
2835 or when a function is declared as
2839 this should only be done for static variables.
2842 Parameters however are not allowed any storage class, (storage classes for
2843 parameters will be ignored), their allocation is governed by the memory
2844 model in use, and the reentrancy options.
2850 For non-reentrant functions SDCC will try to reduce internal ram space usage
2851 by overlaying parameters and local variables of a function (if possible).
2852 Parameters and local variables of a function will be allocated to an overlayabl
2853 e segment if the function has
2855 no other function calls and the function is non-reentrant and the memory
2859 If an explicit storage class is specified for a local variable, it will
2863 Note that the compiler (not the linkage editor) makes the decision for overlayin
2865 Functions that are called from an interrupt service routine should be preceded
2866 by a #pragma\SpecialChar ~
2867 NOOVERLAY if they are not reentrant.
2870 Also note that the compiler does not do any processing of inline assembler
2871 code, so the compiler might incorrectly assign local variables and parameters
2872 of a function into the overlay segment if the inline assembler code calls
2873 other c-functions that might use the overlay.
2874 In that case the #pragma\SpecialChar ~
2875 NOOVERLAY should be used.
2878 Parameters and Local variables of functions that contain 16 or 32 bit multiplica
2879 tion or division will NOT be overlayed since these are implemented using
2880 external functions, e.g.:
2890 void set_error(unsigned char errcd)
2906 void some_isr () interrupt 2 using 1
2935 In the above example the parameter
2943 would be assigned to the overlayable segment if the #pragma\SpecialChar ~
2945 not present, this could cause unpredictable runtime behavior when called
2947 The #pragma\SpecialChar ~
2948 NOOVERLAY ensures that the parameters and local variables for
2949 the function are NOT overlayed.
2952 Interrupt Service Routines
2955 SDCC allows interrupt service routines to be coded in C, with some extended
2962 void timer_isr (void) interrupt 2 using 1
2975 The number following the
2979 keyword is the interrupt number this routine will service.
2980 The compiler will insert a call to this routine in the interrupt vector
2981 table for the interrupt number specified.
2986 keyword is used to tell the compiler to use the specified register bank
2987 (8051 specific) when generating code for this function.
2988 Note that when some function is called from an interrupt service routine
2989 it should be preceded by a #pragma\SpecialChar ~
2990 NOOVERLAY if it is not reentrant.
2991 A special note here, int (16 bit) and long (32 bit) integer division, multiplic
2992 ation & modulus operations are implemented using external support routines
2993 developed in ANSI-C, if an interrupt service routine needs to do any of
2994 these operations then the support routines (as mentioned in a following
2995 section) will have to be recompiled using the
2999 option and the source file will need to be compiled using the
3006 If you have multiple source files in your project, interrupt service routines
3007 can be present in any of them, but a prototype of the isr MUST be present
3008 or included in the file that contains the function
3015 Interrupt Numbers and the corresponding address & descriptions for the Standard
3016 8051 are listed below.
3017 SDCC will automatically adjust the interrupt vector table to the maximum
3018 interrupt number specified.
3024 \begin_inset Tabular
3025 <lyxtabular version="3" rows="6" columns="3">
3027 <column alignment="center" valignment="top" leftline="true" width="0pt">
3028 <column alignment="center" valignment="top" leftline="true" width="0pt">
3029 <column alignment="center" valignment="top" leftline="true" rightline="true" width="0pt">
3030 <row topline="true" bottomline="true">
3031 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3039 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3047 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3056 <row topline="true">
3057 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3065 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3073 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3082 <row topline="true">
3083 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3091 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3099 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3108 <row topline="true">
3109 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3117 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3125 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3134 <row topline="true">
3135 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3143 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3151 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3160 <row topline="true" bottomline="true">
3161 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3169 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3177 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3194 If the interrupt service routine is defined without
3198 a register bank or with register bank 0 (using 0), the compiler will save
3199 the registers used by itself on the stack upon entry and restore them at
3200 exit, however if such an interrupt service routine calls another function
3201 then the entire register bank will be saved on the stack.
3202 This scheme may be advantageous for small interrupt service routines which
3203 have low register usage.
3206 If the interrupt service routine is defined to be using a specific register
3211 are save and restored, if such an interrupt service routine calls another
3212 function (using another register bank) then the entire register bank of
3213 the called function will be saved on the stack.
3214 This scheme is recommended for larger interrupt service routines.
3217 Calling other functions from an interrupt service routine is not recommended,
3218 avoid it if possible.
3222 Also see the _naked modifier.
3230 <TODO: this isn't implemented at all!>
3236 A special keyword may be associated with a function declaring it as
3241 SDCC will generate code to disable all interrupts upon entry to a critical
3242 function and enable them back before returning.
3243 Note that nesting critical functions may cause unpredictable results.
3268 The critical attribute maybe used with other attributes like
3276 A special keyword may be associated with a function declaring it as
3285 function modifier attribute prevents the compiler from generating prologue
3286 and epilogue code for that function.
3287 This means that the user is entirely responsible for such things as saving
3288 any registers that may need to be preserved, selecting the proper register
3289 bank, generating the
3293 instruction at the end, etc.
3294 Practically, this means that the contents of the function must be written
3295 in inline assembler.
3296 This is particularly useful for interrupt functions, which can have a large
3297 (and often unnecessary) prologue/epilogue.
3298 For example, compare the code generated by these two functions:
3304 data unsigned char counter;
3306 void simpleInterrupt(void) interrupt 1
3320 void nakedInterrupt(void) interrupt 2 _naked
3353 ; MUST explicitly include ret in _naked function.
3367 For an 8051 target, the generated simpleInterrupt looks like:
3512 whereas nakedInterrupt looks like:
3537 ; MUST explicitly include ret(i) in _naked function.
3543 While there is nothing preventing you from writing C code inside a _naked
3544 function, there are many ways to shoot yourself in the foot doing this,
3545 and it is recommended that you stick to inline assembler.
3548 Functions using private banks
3555 attribute (which tells the compiler to use a register bank other than the
3556 default bank zero) should only be applied to
3560 functions (see note 1 below).
3561 This will in most circumstances make the generated ISR code more efficient
3562 since it will not have to save registers on the stack.
3569 attribute will have no effect on the generated code for a
3573 function (but may occasionally be useful anyway
3579 possible exception: if a function is called ONLY from 'interrupt' functions
3580 using a particular bank, it can be declared with the same 'using' attribute
3581 as the calling 'interrupt' functions.
3582 For instance, if you have several ISRs using bank one, and all of them
3583 call memcpy(), it might make sense to create a specialized version of memcpy()
3584 'using 1', since this would prevent the ISR from having to save bank zero
3585 to the stack on entry and switch to bank zero before calling the function
3592 (pending: I don't think this has been done yet)
3599 function using a non-zero bank will assume that it can trash that register
3600 bank, and will not save it.
3601 Since high-priority interrupts can interrupt low-priority ones on the 8051
3602 and friends, this means that if a high-priority ISR
3606 a particular bank occurs while processing a low-priority ISR
3610 the same bank, terrible and bad things can happen.
3611 To prevent this, no single register bank should be
3615 by both a high priority and a low priority ISR.
3616 This is probably most easily done by having all high priority ISRs use
3617 one bank and all low priority ISRs use another.
3618 If you have an ISR which can change priority at runtime, you're on your
3619 own: I suggest using the default bank zero and taking the small performance
3623 It is most efficient if your ISR calls no other functions.
3624 If your ISR must call other functions, it is most efficient if those functions
3625 use the same bank as the ISR (see note 1 below); the next best is if the
3626 called functions use bank zero.
3627 It is very inefficient to call a function using a different, non-zero bank
3635 Data items can be assigned an absolute address with the
3639 keyword, in addition to a storage class, e.g.:
3645 xdata at 0x8000 unsigned char PORTA_8255 ;
3651 In the above example the PORTA_8255 will be allocated to the location 0x8000
3652 of the external ram.
3653 Note that this feature is provided to give the programmer access to
3657 devices attached to the controller.
3658 The compiler does not actually reserve any space for variables declared
3659 in this way (they are implemented with an equate in the assembler).
3660 Thus it is left to the programmer to make sure there are no overlaps with
3661 other variables that are declared without the absolute address.
3662 The assembler listing file (.lst) and the linker output files (.rst) and
3663 (.map) are a good places to look for such overlaps.
3667 Absolute address can be specified for variables in all storage classes,
3680 The above example will allocate the variable at offset 0x02 in the bit-addressab
3682 There is no real advantage to assigning absolute addresses to variables
3683 in this manner, unless you want strict control over all the variables allocated.
3689 The compiler inserts a call to the C routine
3691 _sdcc__external__startup()
3696 at the start of the CODE area.
3697 This routine is in the runtime library.
3698 By default this routine returns 0, if this routine returns a non-zero value,
3699 the static & global variable initialization will be skipped and the function
3700 main will be invoked Other wise static & global variables will be initialized
3701 before the function main is invoked.
3704 _sdcc__external__startup()
3706 routine to your program to override the default if you need to setup hardware
3707 or perform some other critical operation prior to static & global variable
3711 Inline Assembler Code
3714 SDCC allows the use of in-line assembler with a few restriction as regards
3716 All labels defined within inline assembler code
3724 where nnnn is a number less than 100 (which implies a limit of utmost 100
3725 inline assembler labels
3733 It is strongly recommended that each assembly instruction (including labels)
3734 be placed in a separate line (as the example shows).
3739 command line option is used, the inline assembler code will be passed through
3740 the peephole optimizer.
3741 This might cause some unexpected changes in the inline assembler code.
3742 Please go throught the peephole optimizer rules defined in file
3746 carefully before using this option.
3786 The inline assembler code can contain any valid code understood by the assembler
3787 , this includes any assembler directives and comment lines.
3788 The compiler does not do any validation of the code within the
3798 Inline assembler code cannot reference any C-Labels, however it can reference
3799 labels defined by the inline assembler, e.g.:
3825 ; some assembler code
3845 /* some more c code */
3847 clabel:\SpecialChar ~
3849 /* inline assembler cannot reference this label */
3861 $0003: ;label (can be reference by inline assembler only)
3873 /* some more c code */
3881 In other words inline assembly code can access labels defined in inline
3882 assembly within the scope of the funtion.
3886 The same goes the other way, ie.
3887 labels defines in inline assembly CANNOT be accessed by C statements.
3890 int (16 bit) and long (32 bit) Support
3893 For signed & unsigned int (16 bit) and long (32 bit) variables, division,
3894 multiplication and modulus operations are implemented by support routines.
3895 These support routines are all developed in ANSI-C to facilitate porting
3896 to other MCUs, although some model specific assembler optimations are used.
3897 The following files contain the described routine, all of them can be found
3898 in <installdir>/share/sdcc/lib.
3904 <pending: tabularise this>
3910 _mulsint.c - signed 16 bit multiplication (calls _muluint)
3912 _muluint.c - unsigned 16 bit multiplication
3914 _divsint.c - signed 16 bit division (calls _divuint)
3916 _divuint.c - unsigned 16 bit division
3918 _modsint.c - signed 16 bit modulus (call _moduint)
3920 _moduint.c - unsigned 16 bit modulus
3922 _mulslong.c - signed 32 bit multiplication (calls _mululong)
3924 _mululong.c - unsigned32 bit multiplication
3926 _divslong.c - signed 32 division (calls _divulong)
3928 _divulong.c - unsigned 32 division
3930 _modslong.c - signed 32 bit modulus (calls _modulong)
3932 _modulong.c - unsigned 32 bit modulus
3940 Since they are compiled as
3944 , interrupt service routines should not do any of the above operations.
3945 If this is unavoidable then the above routines will need to be compiled
3950 option, after which the source program will have to be compiled with
3957 Floating Point Support
3960 SDCC supports IEEE (single precision 4bytes) floating point numbers.The floating
3961 point support routines are derived from gcc's floatlib.c and consists of
3962 the following routines:
3968 <pending: tabularise this>
3974 _fsadd.c - add floating point numbers
3976 _fssub.c - subtract floating point numbers
3978 _fsdiv.c - divide floating point numbers
3980 _fsmul.c - multiply floating point numbers
3982 _fs2uchar.c - convert floating point to unsigned char
3984 _fs2char.c - convert floating point to signed char
3986 _fs2uint.c - convert floating point to unsigned int
3988 _fs2int.c - convert floating point to signed int
3990 _fs2ulong.c - convert floating point to unsigned long
3992 _fs2long.c - convert floating point to signed long
3994 _uchar2fs.c - convert unsigned char to floating point
3996 _char2fs.c - convert char to floating point number
3998 _uint2fs.c - convert unsigned int to floating point
4000 _int2fs.c - convert int to floating point numbers
4002 _ulong2fs.c - convert unsigned long to floating point number
4004 _long2fs.c - convert long to floating point number
4012 Note if all these routines are used simultaneously the data space might
4014 For serious floating point usage it is strongly recommended that the large
4021 SDCC allows two memory models for MCS51 code, small and large.
4022 Modules compiled with different memory models should
4026 be combined together or the results would be unpredictable.
4027 The library routines supplied with the compiler are compiled as both small
4029 The compiled library modules are contained in seperate directories as small
4030 and large so that you can link to either set.
4034 When the large model is used all variables declared without a storage class
4035 will be allocated into the external ram, this includes all parameters and
4036 local variables (for non-reentrant functions).
4037 When the small model is used variables without storage class are allocated
4038 in the internal ram.
4041 Judicious usage of the processor specific storage classes and the 'reentrant'
4042 function type will yield much more efficient code, than using the large
4044 Several optimizations are disabled when the program is compiled using the
4045 large model, it is therefore strongly recommdended that the small model
4046 be used unless absolutely required.
4052 The only model supported is Flat 24.
4053 This generates code for the 24 bit contiguous addressing mode of the Dallas
4055 In this mode, up to four meg of external RAM or code space can be directly
4057 See the data sheets at www.dalsemi.com for further information on this part.
4061 In older versions of the compiler, this option was used with the MCS51 code
4067 Now, however, the '390 has it's own code generator, selected by the
4076 Note that the compiler does not generate any code to place the processor
4077 into 24 bitmode (although
4081 in the ds390 libraries will do that for you).
4086 , the boot loader or similar code must ensure that the processor is in 24
4087 bit contiguous addressing mode before calling the SDCC startup code.
4095 option, variables will by default be placed into the XDATA segment.
4100 Segments may be placed anywhere in the 4 meg address space using the usual
4102 Note that if any segments are located above 64K, the -r flag must be passed
4103 to the linker to generate the proper segment relocations, and the Intel
4104 HEX output format must be used.
4105 The -r flag can be passed to the linker by using the option
4109 on the sdcc command line.
4110 However, currently the linker can not handle code segments > 64k.
4113 Defines Created by the Compiler
4116 The compiler creates the following #defines.
4119 SDCC - this Symbol is always defined.
4122 SDCC_mcs51 or SDCC_ds390 or SDCC_z80, etc - depending on the model used
4126 __mcs51 or __ds390 or __z80, etc - depending on the model used (e.g.
4130 SDCC_STACK_AUTO - this symbol is defined when
4137 SDCC_MODEL_SMALL - when
4144 SDCC_MODEL_LARGE - when
4151 SDCC_USE_XSTACK - when
4158 SDCC_STACK_TENBIT - when
4165 SDCC_MODEL_FLAT24 - when
4178 SDCC performs a host of standard optimizations in addition to some MCU specific
4181 \layout Subsubsection
4183 Sub-expression Elimination
4186 The compiler does local and global common subexpression elimination, e.g.:
4201 will be translated to
4217 Some subexpressions are not as obvious as the above example, e.g.:
4231 In this case the address arithmetic a->b[i] will be computed only once;
4232 the equivalent code in C would be.
4248 The compiler will try to keep these temporary variables in registers.
4249 \layout Subsubsection
4251 Dead-Code Elimination
4266 i = 1; \SpecialChar ~
4271 global = 1;\SpecialChar ~
4284 global = 3;\SpecialChar ~
4299 int global; void f ()
4312 \layout Subsubsection
4373 Note: the dead stores created by this copy propagation will be eliminated
4374 by dead-code elimination.
4375 \layout Subsubsection
4380 Two types of loop optimizations are done by SDCC loop invariant lifting
4381 and strength reduction of loop induction variables.
4382 In addition to the strength reduction the optimizer marks the induction
4383 variables and the register allocator tries to keep the induction variables
4384 in registers for the duration of the loop.
4385 Because of this preference of the register allocator, loop induction optimizati
4386 on causes an increase in register pressure, which may cause unwanted spilling
4387 of other temporary variables into the stack / data space.
4388 The compiler will generate a warning message when it is forced to allocate
4389 extra space either on the stack or data space.
4390 If this extra space allocation is undesirable then induction optimization
4391 can be eliminated either for the entire source file (with ---noinduction
4392 option) or for a given function only using #pragma\SpecialChar ~
4403 for (i = 0 ; i < 100 ; i ++)
4421 for (i = 0; i < 100; i++)
4431 As mentioned previously some loop invariants are not as apparent, all static
4432 address computations are also moved out of the loop.
4436 Strength Reduction, this optimization substitutes an expression by a cheaper
4443 for (i=0;i < 100; i++)
4463 for (i=0;i< 100;i++) {
4467 ar[itemp1] = itemp2;
4483 The more expensive multiplication is changed to a less expensive addition.
4484 \layout Subsubsection
4489 This optimization is done to reduce the overhead of checking loop boundaries
4490 for every iteration.
4491 Some simple loops can be reversed and implemented using a
4492 \begin_inset Quotes eld
4495 decrement and jump if not zero
4496 \begin_inset Quotes erd
4500 SDCC checks for the following criterion to determine if a loop is reversible
4501 (note: more sophisticated compilers use data-dependency analysis to make
4502 this determination, SDCC uses a more simple minded analysis).
4505 The 'for' loop is of the form
4511 for (<symbol> = <expression> ; <sym> [< | <=] <expression> ; [<sym>++ |
4521 The <for body> does not contain
4522 \begin_inset Quotes eld
4526 \begin_inset Quotes erd
4530 \begin_inset Quotes erd
4536 All goto's are contained within the loop.
4539 No function calls within the loop.
4542 The loop control variable <sym> is not assigned any value within the loop
4545 The loop control variable does NOT participate in any arithmetic operation
4549 There are NO switch statements in the loop.
4550 \layout Subsubsection
4552 Algebraic Simplifications
4555 SDCC does numerous algebraic simplifications, the following is a small sub-set
4556 of these optimizations.
4562 i = j + 0 ; /* changed to */ i = j;
4564 i /= 2; /* changed to */ i >>= 1;
4566 i = j - j ; /* changed to */ i = 0;
4568 i = j / 1 ; /* changed to */ i = j;
4574 Note the subexpressions given above are generally introduced by macro expansions
4575 or as a result of copy/constant propagation.
4576 \layout Subsubsection
4581 SDCC changes switch statements to jump tables when the following conditions
4586 The case labels are in numerical sequence, the labels need not be in order,
4587 and the starting number need not be one or zero.
4593 switch(i) {\SpecialChar ~
4700 Both the above switch statements will be implemented using a jump-table.
4703 The number of case labels is at least three, since it takes two conditional
4704 statements to handle the boundary conditions.
4707 The number of case labels is less than 84, since each label takes 3 bytes
4708 and a jump-table can be utmost 256 bytes long.
4712 Switch statements which have gaps in the numeric sequence or those that
4713 have more that 84 case labels can be split into more than one switch statement
4714 for efficient code generation, e.g.:
4752 If the above switch statement is broken down into two switch statements
4786 case 9: \SpecialChar ~
4796 case 12:\SpecialChar ~
4806 then both the switch statements will be implemented using jump-tables whereas
4807 the unmodified switch statement will not be.
4808 \layout Subsubsection
4810 Bit-shifting Operations.
4813 Bit shifting is one of the most frequently used operation in embedded programmin
4815 SDCC tries to implement bit-shift operations in the most efficient way
4835 generates the following code:
4853 In general SDCC will never setup a loop if the shift count is known.
4893 Note that SDCC stores numbers in little-endian format (i.e.
4894 lowest order first).
4895 \layout Subsubsection
4900 A special case of the bit-shift operation is bit rotation, SDCC recognizes
4901 the following expression to be a left bit-rotation:
4912 i = ((i << 1) | (i >> 7));
4920 will generate the following code:
4936 SDCC uses pattern matching on the parse tree to determine this operation.Variatio
4937 ns of this case will also be recognized as bit-rotation, i.e.:
4943 i = ((i >> 7) | (i << 1)); /* left-bit rotation */
4944 \layout Subsubsection
4949 It is frequently required to obtain the highest order bit of an integral
4950 type (long, int, short or char types).
4951 SDCC recognizes the following expression to yield the highest order bit
4952 and generates optimized code for it, e.g.:
4973 hob = (gint >> 15) & 1;
4986 will generate the following code:
5025 000A E5*01\SpecialChar ~
5053 000C 33\SpecialChar ~
5084 000D E4\SpecialChar ~
5115 000E 13\SpecialChar ~
5146 000F F5*02\SpecialChar ~
5176 Variations of this case however will
5181 It is a standard C expression, so I heartily recommend this be the only
5182 way to get the highest order bit, (it is portable).
5183 Of course it will be recognized even if it is embedded in other expressions,
5190 xyz = gint + ((gint >> 15) & 1);
5196 will still be recognized.
5197 \layout Subsubsection
5202 The compiler uses a rule based, pattern matching and re-writing mechanism
5203 for peep-hole optimization.
5208 a peep-hole optimizer by Christopher W.
5209 Fraser (cwfraser@microsoft.com).
5210 A default set of rules are compiled into the compiler, additional rules
5211 may be added with the
5213 ---peep-file <filename>
5216 The rule language is best illustrated with examples.
5244 The above rule will change the following assembly sequence:
5274 Note: All occurrences of a
5278 (pattern variable) must denote the same string.
5279 With the above rule, the assembly sequence:
5297 will remain unmodified.
5301 Other special case optimizations may be added by the user (via
5307 some variants of the 8051 MCU allow only
5316 The following two rules will change all
5338 replace { lcall %1 } by { acall %1 }
5340 replace { ljmp %1 } by { ajmp %1 }
5348 inline-assembler code
5350 is also passed through the peep hole optimizer, thus the peephole optimizer
5351 can also be used as an assembly level macro expander.
5352 The rules themselves are MCU dependent whereas the rule language infra-structur
5353 e is MCU independent.
5354 Peephole optimization rules for other MCU can be easily programmed using
5359 The syntax for a rule is as follows:
5365 rule := replace [ restart ] '{' <assembly sequence> '
5403 <assembly sequence> '
5421 '}' [if <functionName> ] '
5429 <assembly sequence> := assembly instruction (each instruction including
5430 labels must be on a separate line).
5434 The optimizer will apply to the rules one by one from the top in the sequence
5435 of their appearance, it will terminate when all rules are exhausted.
5436 If the 'restart' option is specified, then the optimizer will start matching
5437 the rules again from the top, this option for a rule is expensive (performance)
5438 , it is intended to be used in situations where a transformation will trigger
5439 the same rule again.
5440 An example of this (not a good one, it has side effects) is the following
5467 Note that the replace pattern cannot be a blank, but can be a comment line.
5468 Without the 'restart' option only the inner most 'pop' 'push' pair would
5469 be eliminated, i.e.:
5521 the restart option the rule will be applied again to the resulting code
5522 and then all the pop-push pairs will be eliminated to yield:
5540 A conditional function can be attached to a rule.
5541 Attaching rules are somewhat more involved, let me illustrate this with
5572 The optimizer does a look-up of a function name table defined in function
5577 in the source file SDCCpeeph.c, with the name
5582 If it finds a corresponding entry the function is called.
5583 Note there can be no parameters specified for these functions, in this
5588 is crucial, since the function
5592 expects to find the label in that particular variable (the hash table containin
5593 g the variable bindings is passed as a parameter).
5594 If you want to code more such functions, take a close look at the function
5595 labelInRange and the calling mechanism in source file SDCCpeeph.c.
5596 I know this whole thing is a little kludgey, but maybe some day we will
5597 have some better means.
5598 If you are looking at this file, you will also see the default rules that
5599 are compiled into the compiler, you can add your own rules in the default
5600 set there if you get tired of specifying the ---peep-file option.
5606 SDCC supports the following #pragma directives.
5607 This directives are applicable only at a function level.
5610 SAVE - this will save all the current options.
5613 RESTORE - will restore the saved options from the last save.
5614 Note that SAVES & RESTOREs cannot be nested.
5615 SDCC uses the same buffer to save the options each time a SAVE is called.
5618 NOGCSE - will stop global subexpression elimination.
5621 NOINDUCTION - will stop loop induction optimizations.
5624 NOJTBOUND - will not generate code for boundary value checking, when switch
5625 statements are turned into jump-tables.
5628 NOOVERLAY - the compiler will not overlay the parameters and local variables
5632 NOLOOPREVERSE - Will not do loop reversal optimization
5635 EXCLUDE NONE | {acc[,b[,dpl[,dph]]] - The exclude pragma disables generation
5636 of pair of push/pop instruction in ISR function (using interrupt keyword).
5637 The directive should be placed immediately before the ISR function definition
5638 and it affects ALL ISR functions following it.
5639 To enable the normal register saving for ISR functions use #pragma\SpecialChar ~
5640 EXCLUDE\SpecialChar ~
5644 NOIV - Do not generate interrupt vector table entries for all ISR functions
5645 defined after the pragma.
5646 This is useful in cases where the interrupt vector table must be defined
5647 manually, or when there is a secondary, manually defined interrupt vector
5649 for the autovector feature of the Cypress EZ-USB FX2).
5652 CALLEE-SAVES function1[,function2[,function3...]] - The compiler by default
5653 uses a caller saves convention for register saving across function calls,
5654 however this can cause unneccessary register pushing & popping when calling
5655 small functions from larger functions.
5656 This option can be used to switch the register saving convention for the
5657 function names specified.
5658 The compiler will not save registers when calling these functions, extra
5659 code will be generated at the entry & exit for these functions to save
5660 & restore the registers used by these functions, this can SUBSTANTIALLY
5661 reduce code & improve run time performance of the generated code.
5662 In future the compiler (with interprocedural analysis) will be able to
5663 determine the appropriate scheme to use for each function call.
5664 If ---callee-saves command line option is used, the function names specified
5665 in #pragma\SpecialChar ~
5666 CALLEE-SAVES is appended to the list of functions specified inthe
5670 The pragma's are intended to be used to turn-off certain optimizations which
5671 might cause the compiler to generate extra stack / data space to store
5672 compiler generated temporary variables.
5673 This usually happens in large functions.
5674 Pragma directives should be used as shown in the following example, they
5675 are used to control options & optimizations for a given function; pragmas
5676 should be placed before and/or after a function, placing pragma's inside
5677 a function body could have unpredictable results.
5683 #pragma SAVE /* save the current settings */
5685 #pragma NOGCSE /* turnoff global subexpression elimination */
5687 #pragma NOINDUCTION /* turn off induction optimizations */
5709 #pragma RESTORE /* turn the optimizations back on */
5715 The compiler will generate a warning message when extra space is allocated.
5716 It is strongly recommended that the SAVE and RESTORE pragma's be used when
5717 changing options for a function.
5722 <pending: this is messy and incomplete>
5727 Compiler support routines (_gptrget, _mulint etc)
5730 Stdclib functions (puts, printf, strcat etc)
5733 Math functions (sin, pow, sqrt etc)
5736 Interfacing with Assembly Routines
5737 \layout Subsubsection
5739 Global Registers used for Parameter Passing
5742 The compiler always uses the global registers
5750 to pass the first parameter to a routine.
5751 The second parameter onwards is either allocated on the stack (for reentrant
5752 routines or if ---stack-auto is used) or in the internal / external ram
5753 (depending on the memory model).
5755 \layout Subsubsection
5757 Assembler Routine(non-reentrant)
5760 In the following example the function cfunc calls an assembler routine asm_func,
5761 which takes two parameters.
5767 extern int asm_func(unsigned char, unsigned char);
5771 int c_func (unsigned char i, unsigned char j)
5779 return asm_func(i,j);
5793 return c_func(10,9);
5801 The corresponding assembler function is:
5807 .globl _asm_func_PARM_2
5871 add a,_asm_func_PARM_2
5907 Note here that the return values are placed in 'dpl' - One byte return value,
5908 'dpl' LSB & 'dph' MSB for two byte values.
5909 'dpl', 'dph' and 'b' for three byte values (generic pointers) and 'dpl','dph','
5910 b' & 'acc' for four byte values.
5913 The parameter naming convention is _<function_name>_PARM_<n>, where n is
5914 the parameter number starting from 1, and counting from the left.
5915 The first parameter is passed in
5916 \begin_inset Quotes eld
5920 \begin_inset Quotes erd
5923 for One bye parameter,
5924 \begin_inset Quotes eld
5928 \begin_inset Quotes erd
5932 \begin_inset Quotes eld
5936 \begin_inset Quotes erd
5940 \begin_inset Quotes eld
5944 \begin_inset Quotes erd
5947 for four bytes, the varible name for the second parameter will be _<function_na
5952 Assemble the assembler routine with the following command:
5959 asx8051 -losg asmfunc.asm
5966 Then compile and link the assembler routine to the C source file with the
5974 sdcc cfunc.c asmfunc.rel
5975 \layout Subsubsection
5977 Assembler Routine(reentrant)
5980 In this case the second parameter onwards will be passed on the stack, the
5981 parameters are pushed from right to left i.e.
5982 after the call the left most parameter will be on the top of the stack.
5989 extern int asm_func(unsigned char, unsigned char);
5993 int c_func (unsigned char i, unsigned char j) reentrant
6001 return asm_func(i,j);
6015 return c_func(10,9);
6023 The corresponding assembler routine is:
6133 The compiling and linking procedure remains the same, however note the extra
6134 entry & exit linkage required for the assembler code, _bp is the stack
6135 frame pointer and is used to compute the offset into the stack for parameters
6136 and local variables.
6142 The external stack is located at the start of the external ram segment,
6143 and is 256 bytes in size.
6144 When ---xstack option is used to compile the program, the parameters and
6145 local variables of all reentrant functions are allocated in this area.
6146 This option is provided for programs with large stack space requirements.
6147 When used with the ---stack-auto option, all parameters and local variables
6148 are allocated on the external stack (note support libraries will need to
6149 be recompiled with the same options).
6152 The compiler outputs the higher order address byte of the external ram segment
6153 into PORT P2, therefore when using the External Stack option, this port
6154 MAY NOT be used by the application program.
6160 Deviations from the compliancy.
6163 functions are not always reentrant.
6166 structures cannot be assigned values directly, cannot be passed as function
6167 parameters or assigned to each other and cannot be a return value from
6194 s1 = s2 ; /* is invalid in SDCC although allowed in ANSI */
6205 struct s foo1 (struct s parms) /* is invalid in SDCC although allowed in
6227 return rets;/* is invalid in SDCC although allowed in ANSI */
6232 'long long' (64 bit integers) not supported.
6235 'double' precision floating point not supported.
6238 No support for setjmp and longjmp (for now).
6241 Old K&R style function declarations are NOT allowed.
6247 foo(i,j) /* this old style of function declarations */
6249 int i,j; /* are valid in ANSI but not valid in SDCC */
6263 functions declared as pointers must be dereferenced during the call.
6274 /* has to be called like this */
6276 (*foo)(); /* ansi standard allows calls to be made like 'foo()' */
6279 Cyclomatic Complexity
6282 Cyclomatic complexity of a function is defined as the number of independent
6283 paths the program can take during execution of the function.
6284 This is an important number since it defines the number test cases you
6285 have to generate to validate the function.
6286 The accepted industry standard for complexity number is 10, if the cyclomatic
6287 complexity reported by SDCC exceeds 10 you should think about simplification
6288 of the function logic.
6289 Note that the complexity level is not related to the number of lines of
6291 Large functions can have low complexity, and small functions can have large
6297 SDCC uses the following formula to compute the complexity:
6302 complexity = (number of edges in control flow graph) - (number of nodes
6303 in control flow graph) + 2;
6307 Having said that the industry standard is 10, you should be aware that in
6308 some cases it be may unavoidable to have a complexity level of less than
6310 For example if you have switch statement with more than 10 case labels,
6311 each case label adds one to the complexity level.
6312 The complexity level is by no means an absolute measure of the algorithmic
6313 complexity of the function, it does however provide a good starting point
6314 for which functions you might look at for further optimization.
6320 Here are a few guidelines that will help the compiler generate more efficient
6321 code, some of the tips are specific to this compiler others are generally
6322 good programming practice.
6325 Use the smallest data type to represent your data-value.
6326 If it is known in advance that the value is going to be less than 256 then
6327 use an 'unsigned char' instead of a 'short' or 'int'.
6330 Use unsigned when it is known in advance that the value is not going to
6332 This helps especially if you are doing division or multiplication.
6335 NEVER jump into a LOOP.
6338 Declare the variables to be local whenever possible, especially loop control
6339 variables (induction).
6342 Since the compiler does not always do implicit integral promotion, the programme
6343 r should do an explicit cast when integral promotion is required.
6346 Reducing the size of division, multiplication & modulus operations can reduce
6347 code size substantially.
6348 Take the following code for example.
6354 foobar(unsigned int p1, unsigned char ch)
6358 unsigned char ch1 = p1 % ch ;
6369 For the modulus operation the variable ch will be promoted to unsigned int
6370 first then the modulus operation will be performed (this will lead to a
6371 call to support routine _moduint()), and the result will be casted to a
6373 If the code is changed to
6379 foobar(unsigned int p1, unsigned char ch)
6383 unsigned char ch1 = (unsigned char)p1 % ch ;
6394 It would substantially reduce the code generated (future versions of the
6395 compiler will be smart enough to detect such optimization oppurtunities).
6398 Notes on MCS51 memory layout
6401 The 8051 family of micro controller have a minimum of 128 bytes of internal
6402 memory which is structured as follows
6406 - Bytes 00-1F - 32 bytes to hold up to 4 banks of the registers R7 to R7
6409 - Bytes 20-2F - 16 bytes to hold 128 bit variables and
6411 - Bytes 30-7F - 60 bytes for general purpose use.
6415 Normally the SDCC compiler will only utilise the first bank of registers,
6416 but it is possible to specify that other banks of registers should be used
6417 in interrupt routines.
6418 By default, the compiler will place the stack after the last bank of used
6420 if the first 2 banks of registers are used, it will position the base of
6421 the internal stack at address 16 (0X10).
6422 This implies that as the stack grows, it will use up the remaining register
6423 banks, and the 16 bytes used by the 128 bit variables, and 60 bytes for
6424 general purpose use.
6427 By default, the compiler uses the 60 general purpose bytes to hold "near
6429 The compiler/optimiser may also declare some Local Variables in this area
6434 If any of the 128 bit variables are used, or near data is being used then
6435 care needs to be taken to ensure that the stack does not grow so much that
6436 it starts to over write either your bit variables or "near data".
6437 There is no runtime checking to prevent this from happening.
6440 The amount of stack being used is affected by the use of the "internal stack"
6441 to save registers before a subroutine call is made (---stack-auto will
6442 declare parameters and local variables on the stack) and the number of
6446 If you detect that the stack is over writing you data, then the following
6448 ---xstack will cause an external stack to be used for saving registers
6449 and (if ---stack-auto is being used) storing parameters and local variables.
6450 However this will produce more code which will be slower to execute.
6454 ---stack-loc will allow you specify the start of the stack, i.e.
6455 you could start it after any data in the general purpose area.
6456 However this may waste the memory not used by the register banks and if
6457 the size of the "near data" increases, it may creep into the bottom of
6461 ---stack-after-data, similar to the ---stack-loc, but it automatically places
6462 the stack after the end of the "near data".
6463 Again this could waste any spare register space.
6466 ---data-loc allows you to specify the start address of the near data.
6467 This could be used to move the "near data" further away from the stack
6468 giving it more room to grow.
6469 This will only work if no bit variables are being used and the stack can
6470 grow to use the bit variable space.
6478 If you find that the stack is over writing your bit variables or "near data"
6479 then the approach which best utilised the internal memory is to position
6480 the "near data" after the last bank of used registers or, if you use bit
6481 variables, after the last bit variable by using the ---data-loc, e.g.
6482 if two register banks are being used and no bit variables, ---data-loc
6483 16, and use the ---stack-after-data option.
6486 If bit variables are being used, another method would be to try and squeeze
6487 the data area in the unused register banks if it will fit, and start the
6488 stack after the last bit variable.
6491 Retargetting for other MCUs.
6494 The issues for retargetting the compiler are far too numerous to be covered
6496 What follows is a brief description of each of the seven phases of the
6497 compiler and its MCU dependency.
6500 Parsing the source and building the annotated parse tree.
6501 This phase is largely MCU independent (except for the language extensions).
6502 Syntax & semantic checks are also done in this phase, along with some initial
6503 optimizations like back patching labels and the pattern matching optimizations
6504 like bit-rotation etc.
6507 The second phase involves generating an intermediate code which can be easy
6508 manipulated during the later phases.
6509 This phase is entirely MCU independent.
6510 The intermediate code generation assumes the target machine has unlimited
6511 number of registers, and designates them with the name iTemp.
6512 The compiler can be made to dump a human readable form of the code generated
6513 by using the ---dumpraw option.
6516 This phase does the bulk of the standard optimizations and is also MCU independe
6518 This phase can be broken down into several sub-phases:
6522 Break down intermediate code (iCode) into basic blocks.
6524 Do control flow & data flow analysis on the basic blocks.
6526 Do local common subexpression elimination, then global subexpression elimination
6528 Dead code elimination
6532 If loop optimizations caused any changes then do 'global subexpression eliminati
6533 on' and 'dead code elimination' again.
6536 This phase determines the live-ranges; by live range I mean those iTemp
6537 variables defined by the compiler that still survive after all the optimization
6539 Live range analysis is essential for register allocation, since these computati
6540 on determines which of these iTemps will be assigned to registers, and for
6544 Phase five is register allocation.
6545 There are two parts to this process.
6549 The first part I call 'register packing' (for lack of a better term).
6550 In this case several MCU specific expression folding is done to reduce
6555 The second part is more MCU independent and deals with allocating registers
6556 to the remaining live ranges.
6557 A lot of MCU specific code does creep into this phase because of the limited
6558 number of index registers available in the 8051.
6561 The Code generation phase is (unhappily), entirely MCU dependent and very
6562 little (if any at all) of this code can be reused for other MCU.
6563 However the scheme for allocating a homogenized assembler operand for each
6564 iCode operand may be reused.
6567 As mentioned in the optimization section the peep-hole optimizer is rule
6568 based system, which can reprogrammed for other MCUs.
6571 SDCDB - Source Level Debugger
6574 SDCC is distributed with a source level debugger.
6575 The debugger uses a command line interface, the command repertoire of the
6576 debugger has been kept as close to gdb (the GNU debugger) as possible.
6577 The configuration and build process is part of the standard compiler installati
6578 on, which also builds and installs the debugger in the target directory
6579 specified during configuration.
6580 The debugger allows you debug BOTH at the C source and at the ASM source
6584 Compiling for Debugging
6589 debug option must be specified for all files for which debug information
6591 The complier generates a .cdb file for each of these files.
6592 The linker updates the .cdb file with the address information.
6593 This .cdb is used by the debugger.
6596 How the Debugger Works
6599 When the ---debug option is specified the compiler generates extra symbol
6600 information some of which are put into the the assembler source and some
6601 are put into the .cdb file, the linker updates the .cdb file with the address
6602 information for the symbols.
6603 The debugger reads the symbolic information generated by the compiler &
6604 the address information generated by the linker.
6605 It uses the SIMULATOR (Daniel's S51) to execute the program, the program
6606 execution is controlled by the debugger.
6607 When a command is issued for the debugger, it translates it into appropriate
6608 commands for the simulator.
6611 Starting the Debugger
6614 The debugger can be started using the following command line.
6615 (Assume the file you are debugging has the file name foo).
6629 The debugger will look for the following files.
6632 foo.c - the source file.
6635 foo.cdb - the debugger symbol information file.
6638 foo.ihx - the intel hex format object file.
6641 Command Line Options.
6644 ---directory=<source file directory> this option can used to specify the
6645 directory search list.
6646 The debugger will look into the directory list specified for source, cdb
6648 The items in the directory list must be separated by ':', e.g.
6649 if the source files can be in the directories /home/src1 and /home/src2,
6650 the ---directory option should be ---directory=/home/src1:/home/src2.
6651 Note there can be no spaces in the option.
6655 -cd <directory> - change to the <directory>.
6658 -fullname - used by GUI front ends.
6661 -cpu <cpu-type> - this argument is passed to the simulator please see the
6662 simulator docs for details.
6665 -X <Clock frequency > this options is passed to the simulator please see
6666 the simulator docs for details.
6669 -s <serial port file> passed to simulator see the simulator docs for details.
6672 -S <serial in,out> passed to simulator see the simulator docs for details.
6678 As mention earlier the command interface for the debugger has been deliberately
6679 kept as close the GNU debugger gdb, as possible.
6680 This will help the integration with existing graphical user interfaces
6681 (like ddd, xxgdb or xemacs) existing for the GNU debugger.
6682 \layout Subsubsection
6684 break [line | file:line | function | file:function]
6687 Set breakpoint at specified line or function:
6696 sdcdb>break foo.c:100
6700 sdcdb>break foo.c:funcfoo
6701 \layout Subsubsection
6703 clear [line | file:line | function | file:function ]
6706 Clear breakpoint at specified line or function:
6715 sdcdb>clear foo.c:100
6719 sdcdb>clear foo.c:funcfoo
6720 \layout Subsubsection
6725 Continue program being debugged, after breakpoint.
6726 \layout Subsubsection
6731 Execute till the end of the current function.
6732 \layout Subsubsection
6737 Delete breakpoint number 'n'.
6738 If used without any option clear ALL user defined break points.
6739 \layout Subsubsection
6741 info [break | stack | frame | registers ]
6744 info break - list all breakpoints
6747 info stack - show the function call stack.
6750 info frame - show information about the current execution frame.
6753 info registers - show content of all registers.
6754 \layout Subsubsection
6759 Step program until it reaches a different source line.
6760 \layout Subsubsection
6765 Step program, proceeding through subroutine calls.
6766 \layout Subsubsection
6771 Start debugged program.
6772 \layout Subsubsection
6777 Print type information of the variable.
6778 \layout Subsubsection
6783 print value of variable.
6784 \layout Subsubsection
6789 load the given file name.
6790 Note this is an alternate method of loading file for debugging.
6791 \layout Subsubsection
6796 print information about current frame.
6797 \layout Subsubsection
6802 Toggle between C source & assembly source.
6803 \layout Subsubsection
6808 Send the string following '!' to the simulator, the simulator response is
6810 Note the debugger does not interpret the command being sent to the simulator,
6811 so if a command like 'go' is sent the debugger can loose its execution
6812 context and may display incorrect values.
6813 \layout Subsubsection
6820 My name is Bobby Brown"
6823 Interfacing with XEmacs.
6826 Two files (in emacs lisp) are provided for the interfacing with XEmacs,
6827 sdcdb.el and sdcdbsrc.el.
6828 These two files can be found in the $(prefix)/bin directory after the installat
6830 These files need to be loaded into XEmacs for the interface to work.
6831 This can be done at XEmacs startup time by inserting the following into
6832 your '.xemacs' file (which can be found in your HOME directory):
6838 (load-file sdcdbsrc.el)
6844 .xemacs is a lisp file so the () around the command is REQUIRED.
6845 The files can also be loaded dynamically while XEmacs is running, set the
6846 environment variable 'EMACSLOADPATH' to the installation bin directory
6847 (<installdir>/bin), then enter the following command ESC-x load-file sdcdbsrc.
6848 To start the interface enter the following command:
6862 You will prompted to enter the file name to be debugged.
6867 The command line options that are passed to the simulator directly are bound
6868 to default values in the file sdcdbsrc.el.
6869 The variables are listed below, these values maybe changed as required.
6872 sdcdbsrc-cpu-type '51
6875 sdcdbsrc-frequency '11059200
6881 The following is a list of key mapping for the debugger interface.
6889 ;; Current Listing ::
6906 binding\SpecialChar ~
6945 ------\SpecialChar ~
6985 sdcdb-next-from-src\SpecialChar ~
7011 sdcdb-back-from-src\SpecialChar ~
7037 sdcdb-cont-from-src\SpecialChar ~
7047 SDCDB continue command
7063 sdcdb-step-from-src\SpecialChar ~
7089 sdcdb-whatis-c-sexp\SpecialChar ~
7099 SDCDB ptypecommand for data at
7163 sdcdbsrc-delete\SpecialChar ~
7177 SDCDB Delete all breakpoints if no arg
7225 given or delete arg (C-u arg x)
7241 sdcdbsrc-frame\SpecialChar ~
7256 SDCDB Display current frame if no arg,
7305 given or display frame arg
7370 sdcdbsrc-goto-sdcdb\SpecialChar ~
7380 Goto the SDCDB output buffer
7396 sdcdb-print-c-sexp\SpecialChar ~
7407 SDCDB print command for data at
7471 sdcdbsrc-goto-sdcdb\SpecialChar ~
7481 Goto the SDCDB output buffer
7497 sdcdbsrc-mode\SpecialChar ~
7513 Toggles Sdcdbsrc mode (turns it off)
7517 ;; C-c C-f\SpecialChar ~
7525 sdcdb-finish-from-src\SpecialChar ~
7533 SDCDB finish command
7537 ;; C-x SPC\SpecialChar ~
7545 sdcdb-break\SpecialChar ~
7563 Set break for line with point
7565 ;; ESC t\SpecialChar ~
7575 sdcdbsrc-mode\SpecialChar ~
7591 Toggle Sdcdbsrc mode
7593 ;; ESC m\SpecialChar ~
7603 sdcdbsrc-srcmode\SpecialChar ~
7627 The Z80 and gbz80 port
7630 SDCC can target both the Zilog Z80 and the Nintendo Gameboy's Z80-like gbz80.
7631 The port is incomplete - long support is incomplete (mul, div and mod are
7632 unimplimented), and both float and bitfield support is missing.
7633 Apart from that the code generated is correct.
7636 As always, the code is the authoritave reference - see z80/ralloc.c and z80/gen.c.
7637 The stack frame is similar to that generated by the IAR Z80 compiler.
7638 IX is used as the base pointer, HL is used as a temporary register, and
7639 BC and DE are available for holding varibles.
7640 IY is currently unusued.
7641 Return values are stored in HL.
7642 One bad side effect of using IX as the base pointer is that a functions
7643 stack frame is limited to 127 bytes - this will be fixed in a later version.
7649 SDCC has grown to be a large project.
7650 The compiler alone (without the preprocessor, assembler and linker) is
7651 about 40,000 lines of code (blank stripped).
7652 The open source nature of this project is a key to its continued growth
7654 You gain the benefit and support of many active software developers and
7656 Is SDCC perfect? No, that's why we need your help.
7657 The developers take pride in fixing reported bugs.
7658 You can help by reporting the bugs and helping other SDCC users.
7659 There are lots of ways to contribute, and we encourage you to take part
7660 in making SDCC a great software package.
7666 Send an email to the mailing list at 'user-sdcc@sdcc.sourceforge.net' or 'devel-sd
7667 cc@sdcc.sourceforge.net'.
7668 Bugs will be fixed ASAP.
7669 When reporting a bug, it is very useful to include a small test program
7670 which reproduces the problem.
7671 If you can isolate the problem by looking at the generated assembly code,
7672 this can be very helpful.
7673 Compiling your program with the ---dumpall option can sometimes be useful
7674 in locating optimization problems.
7677 The anatomy of the compiler
7682 This is an excerpt from an atricle published in Circuit Cellar MagaZine
7684 It's a little outdated (the compiler is much more efficient now and user/devell
7685 oper friendly), but pretty well exposes the guts of it all.
7691 The current version of SDCC can generate code for Intel 8051 and Z80 MCU.
7692 It is fairly easy to retarget for other 8-bit MCU.
7693 Here we take a look at some of the internals of the compiler.
7700 Parsing the input source file and creating an AST (Annotated Syntax Tree).
7701 This phase also involves propagating types (annotating each node of the
7702 parse tree with type information) and semantic analysis.
7703 There are some MCU specific parsing rules.
7704 For example the storage classes, the extended storage classes are MCU specific
7705 while there may be a xdata storage class for 8051 there is no such storage
7706 class for z80 or Atmel AVR.
7707 SDCC allows MCU specific storage class extensions, i.e.
7708 xdata will be treated as a storage class specifier when parsing 8051 C
7709 code but will be treated as a C identifier when parsing z80 or ATMEL AVR
7716 Intermediate code generation.
7717 In this phase the AST is broken down into three-operand form (iCode).
7718 These three operand forms are represented as doubly linked lists.
7719 ICode is the term given to the intermediate form generated by the compiler.
7720 ICode example section shows some examples of iCode generated for some simple
7727 Bulk of the target independent optimizations is performed in this phase.
7728 The optimizations include constant propagation, common sub-expression eliminati
7729 on, loop invariant code movement, strength reduction of loop induction variables
7730 and dead-code elimination.
7736 During intermediate code generation phase, the compiler assumes the target
7737 machine has infinite number of registers and generates a lot of temporary
7739 The live range computation determines the lifetime of each of these compiler-ge
7740 nerated temporaries.
7741 A picture speaks a thousand words.
7742 ICode example sections show the live range annotations for each of the
7744 It is important to note here, each iCode is assigned a number in the order
7745 of its execution in the function.
7746 The live ranges are computed in terms of these numbers.
7747 The from number is the number of the iCode which first defines the operand
7748 and the to number signifies the iCode which uses this operand last.
7754 The register allocation determines the type and number of registers needed
7756 In most MCUs only a few registers can be used for indirect addressing.
7757 In case of 8051 for example the registers R0 & R1 can be used to indirectly
7758 address the internal ram and DPTR to indirectly address the external ram.
7759 The compiler will try to allocate the appropriate register to pointer variables
7761 ICode example section shows the operands annotated with the registers assigned
7763 The compiler will try to keep operands in registers as much as possible;
7764 there are several schemes the compiler uses to do achieve this.
7765 When the compiler runs out of registers the compiler will check to see
7766 if there are any live operands which is not used or defined in the current
7767 basic block being processed, if there are any found then it will push that
7768 operand and use the registers in this block, the operand will then be popped
7769 at the end of the basic block.
7773 There are other MCU specific considerations in this phase.
7774 Some MCUs have an accumulator; very short-lived operands could be assigned
7775 to the accumulator instead of general-purpose register.
7781 Figure II gives a table of iCode operations supported by the compiler.
7782 The code generation involves translating these operations into corresponding
7783 assembly code for the processor.
7784 This sounds overly simple but that is the essence of code generation.
7785 Some of the iCode operations are generated on a MCU specific manner for
7786 example, the z80 port does not use registers to pass parameters so the
7787 SEND and RECV iCode operations will not be generated, and it also does
7788 not support JUMPTABLES.
7795 <Where is Figure II ?>
7801 This section shows some details of iCode.
7802 The example C code does not do anything useful; it is used as an example
7803 to illustrate the intermediate code generated by the compiler.
7816 /* This function does nothing useful.
7823 for the purpose of explaining iCode */
7826 short function (data int *x)
7834 short i=10; /* dead initialization eliminated */
7839 short sum=10; /* dead initialization eliminated */
7852 while (*x) *x++ = *p++;
7866 /* compiler detects i,j to be induction variables */
7870 for (i = 0, j = 10 ; i < 10 ; i++, j---) {
7882 mul += i * 3; /* this multiplication remains */
7888 gint += j * 3;/* this multiplication changed to addition */
7905 In addition to the operands each iCode contains information about the filename
7906 and line it corresponds to in the source file.
7907 The first field in the listing should be interpreted as follows:
7912 Filename(linenumber: iCode Execution sequence number : ICode hash table
7913 key : loop depth of the iCode).
7918 Then follows the human readable form of the ICode operation.
7919 Each operand of this triplet form can be of three basic types a) compiler
7920 generated temporary b) user defined variable c) a constant value.
7921 Note that local variables and parameters are replaced by compiler generated
7923 Live ranges are computed only for temporaries (i.e.
7924 live ranges are not computed for global variables).
7925 Registers are allocated for temporaries only.
7926 Operands are formatted in the following manner:
7931 Operand Name [lr live-from : live-to ] { type information } [ registers
7937 As mentioned earlier the live ranges are computed in terms of the execution
7938 sequence number of the iCodes, for example
7940 the iTemp0 is live from (i.e.
7941 first defined in iCode with execution sequence number 3, and is last used
7942 in the iCode with sequence number 5).
7943 For induction variables such as iTemp21 the live range computation extends
7944 the lifetime from the start to the end of the loop.
7946 The register allocator used the live range information to allocate registers,
7947 the same registers may be used for different temporaries if their live
7948 ranges do not overlap, for example r0 is allocated to both iTemp6 and to
7949 iTemp17 since their live ranges do not overlap.
7950 In addition the allocator also takes into consideration the type and usage
7951 of a temporary, for example itemp6 is a pointer to near space and is used
7952 as to fetch data from (i.e.
7953 used in GET_VALUE_AT_ADDRESS) so it is allocated a pointer registers (r0).
7954 Some short lived temporaries are allocated to special registers which have
7955 meaning to the code generator e.g.
7956 iTemp13 is allocated to a pseudo register CC which tells the back end that
7957 the temporary is used only for a conditional jump the code generation makes
7958 use of this information to optimize a compare and jump ICode.
7960 There are several loop optimizations performed by the compiler.
7961 It can detect induction variables iTemp21(i) and iTemp23(j).
7962 Also note the compiler does selective strength reduction, i.e.
7963 the multiplication of an induction variable in line 18 (gint = j * 3) is
7964 changed to addition, a new temporary iTemp17 is allocated and assigned
7965 a initial value, a constant 3 is then added for each iteration of the loop.
7966 The compiler does not change the multiplication in line 17 however since
7967 the processor does support an 8 * 8 bit multiplication.
7969 Note the dead code elimination optimization eliminated the dead assignments
7970 in line 7 & 8 to I and sum respectively.
7977 Sample.c (5:1:0:0) _entry($9) :
7982 Sample.c(5:2:1:0) proc _function [lr0:0]{function short}
7987 Sample.c(11:3:2:0) iTemp0 [lr3:5]{_near * int}[r2] = recv
7992 Sample.c(11:4:53:0) preHeaderLbl0($11) :
7997 Sample.c(11:5:55:0) iTemp6 [lr5:16]{_near * int}[r0] := iTemp0 [lr3:5]{_near
8003 Sample.c(11:6:5:1) _whilecontinue_0($1) :
8008 Sample.c(11:7:7:1) iTemp4 [lr7:8]{int}[r2 r3] = @[iTemp6 [lr5:16]{_near *
8014 Sample.c(11:8:8:1) if iTemp4 [lr7:8]{int}[r2 r3] == 0 goto _whilebreak_0($3)
8019 Sample.c(11:9:14:1) iTemp7 [lr9:13]{_far * int}[DPTR] := _p [lr0:0]{_far
8025 Sample.c(11:10:15:1) _p [lr0:0]{_far * int} = _p [lr0:0]{_far * int} + 0x2
8031 Sample.c(11:13:18:1) iTemp10 [lr13:14]{int}[r2 r3] = @[iTemp7 [lr9:13]{_far
8037 Sample.c(11:14:19:1) *(iTemp6 [lr5:16]{_near * int}[r0]) := iTemp10 [lr13:14]{int
8043 Sample.c(11:15:12:1) iTemp6 [lr5:16]{_near * int}[r0] = iTemp6 [lr5:16]{_near
8044 * int}[r0] + 0x2 {short}
8049 Sample.c(11:16:20:1) goto _whilecontinue_0($1)
8054 Sample.c(11:17:21:0)_whilebreak_0($3) :
8059 Sample.c(12:18:22:0) iTemp2 [lr18:40]{short}[r2] := 0x0 {short}
8064 Sample.c(13:19:23:0) iTemp11 [lr19:40]{short}[r3] := 0x0 {short}
8069 Sample.c(15:20:54:0)preHeaderLbl1($13) :
8074 Sample.c(15:21:56:0) iTemp21 [lr21:38]{short}[r4] := 0x0 {short}
8079 Sample.c(15:22:57:0) iTemp23 [lr22:38]{int}[r5 r6] := 0xa {int}
8084 Sample.c(15:23:58:0) iTemp17 [lr23:38]{int}[r7 r0] := 0x1e {int}
8089 Sample.c(15:24:26:1)_forcond_0($4) :
8094 Sample.c(15:25:27:1) iTemp13 [lr25:26]{char}[CC] = iTemp21 [lr21:38]{short}[r4]
8100 Sample.c(15:26:28:1) if iTemp13 [lr25:26]{char}[CC] == 0 goto _forbreak_0($7)
8105 Sample.c(16:27:31:1) iTemp2 [lr18:40]{short}[r2] = iTemp2 [lr18:40]{short}[r2]
8106 + ITemp21 [lr21:38]{short}[r4]
8111 Sample.c(17:29:33:1) iTemp15 [lr29:30]{short}[r1] = iTemp21 [lr21:38]{short}[r4]
8117 Sample.c(17:30:34:1) iTemp11 [lr19:40]{short}[r3] = iTemp11 [lr19:40]{short}[r3]
8118 + iTemp15 [lr29:30]{short}[r1]
8123 Sample.c(18:32:36:1:1) iTemp17 [lr23:38]{int}[r7 r0]= iTemp17 [lr23:38]{int}[r7
8129 Sample.c(18:33:37:1) _gint [lr0:0]{int} = _gint [lr0:0]{int} + iTemp17 [lr23:38]{
8135 Sample.c(15:36:42:1) iTemp21 [lr21:38]{short}[r4] = iTemp21 [lr21:38]{short}[r4]
8141 Sample.c(15:37:45:1) iTemp23 [lr22:38]{int}[r5 r6]= iTemp23 [lr22:38]{int}[r5
8147 Sample.c(19:38:47:1) goto _forcond_0($4)
8152 Sample.c(19:39:48:0)_forbreak_0($7) :
8157 Sample.c(20:40:49:0) iTemp24 [lr40:41]{short}[DPTR] = iTemp2 [lr18:40]{short}[r2]
8158 + ITemp11 [lr19:40]{short}[r3]
8163 Sample.c(20:41:50:0) ret iTemp24 [lr40:41]{short}
8168 Sample.c(20:42:51:0)_return($8) :
8173 Sample.c(20:43:52:0) eproc _function [lr0:0]{ ia0 re0 rm0}{function short}
8179 Finally the code generated for this function:
8220 ; ----------------------------------------------
8230 ; ----------------------------------------------
8240 ; iTemp0 [lr3:5]{_near * int}[r2] = recv
8252 ; iTemp6 [lr5:16]{_near * int}[r0] := iTemp0 [lr3:5]{_near * int}[r2]
8264 ;_whilecontinue_0($1) :
8274 ; iTemp4 [lr7:8]{int}[r2 r3] = @[iTemp6 [lr5:16]{_near * int}[r0]]
8279 ; if iTemp4 [lr7:8]{int}[r2 r3] == 0 goto _whilebreak_0($3)
8338 ; iTemp7 [lr9:13]{_far * int}[DPTR] := _p [lr0:0]{_far * int}
8357 ; _p [lr0:0]{_far * int} = _p [lr0:0]{_far * int} + 0x2 {short}
8404 ; iTemp10 [lr13:14]{int}[r2 r3] = @[iTemp7 [lr9:13]{_far * int}[DPTR]]
8444 ; *(iTemp6 [lr5:16]{_near * int}[r0]) := iTemp10 [lr13:14]{int}[r2 r3]
8470 ; iTemp6 [lr5:16]{_near * int}[r0] =
8475 ; iTemp6 [lr5:16]{_near * int}[r0] +
8492 ; goto _whilecontinue_0($1)
8504 ; _whilebreak_0($3) :
8514 ; iTemp2 [lr18:40]{short}[r2] := 0x0 {short}
8526 ; iTemp11 [lr19:40]{short}[r3] := 0x0 {short}
8538 ; iTemp21 [lr21:38]{short}[r4] := 0x0 {short}
8550 ; iTemp23 [lr22:38]{int}[r5 r6] := 0xa {int}
8569 ; iTemp17 [lr23:38]{int}[r7 r0] := 0x1e {int}
8598 ; iTemp13 [lr25:26]{char}[CC] = iTemp21 [lr21:38]{short}[r4] < 0xa {short}
8603 ; if iTemp13 [lr25:26]{char}[CC] == 0 goto _forbreak_0($7)
8648 ; iTemp2 [lr18:40]{short}[r2] = iTemp2 [lr18:40]{short}[r2] +
8653 ; iTemp21 [lr21:38]{short}[r4]
8679 ; iTemp15 [lr29:30]{short}[r1] = iTemp21 [lr21:38]{short}[r4] * 0x3 {short}
8712 ; iTemp11 [lr19:40]{short}[r3] = iTemp11 [lr19:40]{short}[r3] +
8717 ; iTemp15 [lr29:30]{short}[r1]
8736 ; iTemp17 [lr23:38]{int}[r7 r0]= iTemp17 [lr23:38]{int}[r7 r0]- 0x3 {short}
8783 ; _gint [lr0:0]{int} = _gint [lr0:0]{int} + iTemp17 [lr23:38]{int}[r7 r0]
8830 ; iTemp21 [lr21:38]{short}[r4] = iTemp21 [lr21:38]{short}[r4] + 0x1 {short}
8842 ; iTemp23 [lr22:38]{int}[r5 r6]= iTemp23 [lr22:38]{int}[r5 r6]- 0x1 {short}
8856 cjne r5,#0xff,00104$
8868 ; goto _forcond_0($4)
8890 ; ret iTemp24 [lr40:41]{short}
8939 \begin_inset LatexCommand \url{http://sdcc.sourceforge.net#Who}
8949 Thanks to all the other volunteer developers who have helped with coding,
8950 testing, web-page creation, distribution sets, etc.
8951 You know who you are :-)
8958 This document was initially written by Sandeep Dutta
8961 All product names mentioned herein may be trademarks of their respective
8967 \begin_inset LatexCommand \printindex{}
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