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 SDCC Compiler User Guide
33 \begin_inset LatexCommand \tableofcontents{}
50 is a Freeware, retargettable, optimizing ANSI-C compiler by
54 designed for 8 bit Microprocessors.
55 The current version targets Intel MCS51 based Microprocessors(8051,8052,
56 etc), Zilog Z80 based MCUs, and the Dallas DS80C390 variant.
57 It can be retargetted for other microprocessors, support for PIC, AVR and
58 186 is under development.
59 The entire source code for the compiler is distributed under GPL.
60 SDCC uses ASXXXX & ASLINK, a Freeware, retargettable assembler & linker.
61 SDCC has extensive language extensions suitable for utilizing various microcont
62 rollers and underlying hardware effectively.
67 In addition to the MCU specific optimizations SDCC also does a host of standard
71 global sub expression elimination,
74 loop optimizations (loop invariant, strength reduction of induction variables
78 constant folding & propagation,
94 For the back-end SDCC uses a global register allocation scheme which should
95 be well suited for other 8 bit MCUs.
100 The peep hole optimizer uses a rule based substitution mechanism which is
106 Supported data-types are:
109 char (8 bits, 1 byte),
112 short and int (16 bits, 2 bytes),
115 long (32 bit, 4 bytes)
122 The compiler also allows
124 inline assembler code
126 to be embedded anywhere in a function.
127 In addition, routines developed in assembly can also be called.
131 SDCC also provides an option (--cyclomatic) to report the relative complexity
133 These functions can then be further optimized, or hand coded in assembly
139 SDCC also comes with a companion source level debugger SDCDB, the debugger
140 currently uses ucSim a freeware simulator for 8051 and other micro-controllers.
145 The latest version can be downloaded from
146 \begin_inset LatexCommand \htmlurl{http://sdcc.sourceforge.net/}
158 All packages used in this compiler system are
166 ; source code for all the sub-packages (pre-processor, assemblers, linkers
167 etc) is distributed with the package.
168 This documentation is maintained using a freeware word processor (LyX).
170 This program is free software; you can redistribute it and/or modify it
171 under the terms of the GNU General Public License as published by the Free
172 Software Foundation; either version 2, or (at your option) any later version.
173 This program is distributed in the hope that it will be useful, but WITHOUT
174 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
175 FOR A PARTICULAR PURPOSE.
176 See the GNU General Public License for more details.
177 You should have received a copy of the GNU General Public License along
178 with this program; if not, write to the Free Software Foundation, 59 Temple
179 Place - Suite 330, Boston, MA 02111-1307, USA.
180 In other words, you are welcome to use, share and improve this program.
181 You are forbidden to forbid anyone else to use, share and improve what
183 Help stamp out software-hoarding!
186 Typographic conventions
189 Throughout this manual, we will use the following convention.
190 Commands you have to type in are printed in
198 Code samples are printed in
203 Interesting items and new terms are printed in
208 Compatibility with previous versions
211 This version has numerous bug fixes compared with the previous version.
212 But we also introduced some incompatibilities with older versions.
213 Not just for the fun of it, but to make the compiler more stable, efficient
220 short is now equivalent to int (16 bits), it used to be equivalent to char
221 (8 bits) which is not ANSI compliant
224 the default directory where include, library and documention files are stored
225 is now in /usr/local/share
228 char type parameters to vararg functions are casted to int unless explicitly
245 will push a as an int and as a char resp.
248 option --regextend has been removed
251 option --noregparms has been removed
254 option --stack-after-data has been removed
259 <pending: more incompatibilities?>
265 What do you need before you start installation of SDCC? A computer, and
267 The preferred method of installation is to compile SDCC from source using
269 For Windows some pre-compiled binary distributions are available for your
271 You should have some experience with command line tools and compiler use.
277 The SDCC home page at
278 \begin_inset LatexCommand \htmlurl{http://sdcc.sourceforge.net/}
282 is a great place to find distribution sets.
283 You can also find links to the user mailing lists that offer help or discuss
284 SDCC with other SDCC users.
285 Web links to other SDCC related sites can also be found here.
286 This document can be found in the DOC directory of the source package as
288 Some of the other tools (simulator and assembler) included with SDCC contain
289 their own documentation and can be found in the source distribution.
290 If you want the latest unreleased software, the complete source package
291 is available directly by anonymous CVS on cvs.sdcc.sourceforge.net.
294 Wishes for the future
297 There are (and always will be) some things that could be done.
298 Here are some I can think of:
305 char KernelFunction3(char p) at 0x340;
311 If you can think of some more, please send them to the list.
317 <pending: And then of course a proper index-table
318 \begin_inset LatexCommand \index{index}
328 Install and search paths
331 Linux (and other gcc-builds like Solaris, Cygwin, Mingw and OSX) by default
332 install in /usr/local.
333 You can override this when configuring with --prefix-path.
334 Subdirs used will be bin, share/sdcc/include, share/sdcc/lib and share/sdcc/doc.
336 Windows MSVC and Borland builds will install in one single tree (e.g.
337 /sdcc) with subdirs bin, lib, include and doc.
341 The paths searched when running the compiler are as follows (the first catch
345 Binary files (preprocessor, assembler and linker):
347 - the path of argv[0] (if available)
350 \begin_inset Quotes sld
354 \begin_inset Quotes srd
360 \begin_inset Quotes sld
364 \begin_inset Quotes srd
377 \begin_inset Quotes sld
381 \begin_inset Quotes srd
387 \begin_inset Quotes sld
392 - /usr/local/share/sdcc/include (gcc builds)
394 - path(arv[0])/../include and then /sdcc/include (windoze msvc and borland
402 is auto-appended by the compiler, e.g.
403 small, large, z80, ds390 etc.):
408 \begin_inset Quotes sld
412 \begin_inset Quotes srd
422 \begin_inset Quotes sld
426 \begin_inset Quotes srd
435 - /usr/local/share/sdcc/lib/
441 - path(argv[0])/../lib/
449 (windoze msvc and borland builds)
452 Documentation (although never really searched for, you have to do that yourself
456 \begin_inset Quotes sld
460 \begin_inset Quotes srd
465 - /usr/local/share/sdcc/doc (gcc builds)
467 - /sdcc/doc (windoze msvc and borland builds)
470 So, for windoze it is highly recommended to set the environment variable
471 SDCCHOME to prevent needless usage of -I and -L.
474 Linux and other gcc-based systems (cygwin, mingw, osx)
479 Download the source package
481 either from the SDCC CVS repository or from the
482 \begin_inset LatexCommand \url[nightly snapshots]{http://sdcc.sourceforge.net/snap.php}
488 , it will be named something like sdcc
497 Bring up a command line terminal, such as xterm.
502 Unpack the file using a command like:
505 "tar -xzf sdcc.src.tgz
510 , this will create a sub-directory called sdcc with all of the sources.
513 Change directory into the main SDCC directory, for example type:
530 This configures the package for compilation on your system.
546 All of the source packages will compile, this can take a while.
562 This copies the binary executables, the include files, the libraries and
563 the documentation to the install directories.
567 \layout Subsubsection
569 Windows Install Using a Binary Package
572 Download the binary package and unpack it using your favorite unpacking
573 tool (gunzip, WinZip, etc).
574 This should unpack to a group of sub-directories.
575 An example directory structure after unpacking the mingw package is: c:
581 bin for the executables, c:
601 lib for the include and libraries.
604 Adjust your environment variable PATH to include the location of the bin
605 directory or start sdcc using the full path.
606 \layout Subsubsection
608 Windows Install Using Cygwin and Mingw
611 Follow the instruction in
613 Linux and other gcc-based systems
616 \layout Subsubsection
618 Windows Install Using Microsoft Visual C++ 6.0/NET
623 Download the source package
625 either from the SDCC CVS repository or from the
626 \begin_inset LatexCommand \url[nightly snapshots]{http://sdcc.sourceforge.net/snap.php}
632 , it will be named something like sdcc
639 SDCC is distributed with all the projects, workspaces, and files you need
640 to build it using Visual C++ 6.0/NET.
641 The workspace name is 'sdcc.dsw'.
642 Please note that as it is now, all the executables are created in a folder
646 Once built you need to copy the executables from sdcc
650 bin before runnng SDCC.
655 In order to build SDCC with Visual C++ 6.0/NET you need win32 executables
656 of bison.exe, flex.exe, and gawk.exe.
657 One good place to get them is
658 \begin_inset LatexCommand \url[here]{http://unxutils.sourceforge.net}
666 Download the file UnxUtils.zip.
667 Now you have to install the utilities and setup Visual C++ so it can locate
668 the required programs.
669 Here there are two alternatives (choose one!):
676 a) Extract UnxUtils.zip to your C:
678 hard disk PRESERVING the original paths, otherwise bison won't work.
679 (If you are using WinZip make certain that 'Use folder names' is selected)
683 b) In the Visual C++ IDE click Tools, Options, select the Directory tab,
684 in 'Show directories for:' select 'Executable files', and in the directories
685 window add a new path: 'C:
695 (As a side effect, you get a bunch of Unix utilities that could be useful,
696 such as diff and patch.)
703 This one avoids extracting a bunch of files you may not use, but requires
708 a) Create a directory were to put the tools needed, or use a directory already
716 b) Extract 'bison.exe', 'bison.hairy', 'bison.simple', 'flex.exe', and gawk.exe
717 to such directory WITHOUT preserving the original paths.
718 (If you are using WinZip make certain that 'Use folder names' is not selected)
722 c) Rename bison.exe to '_bison.exe'.
726 d) Create a batch file 'bison.bat' in 'C:
730 ' and add these lines:
750 _bison %1 %2 %3 %4 %5 %6 %7 %8 %9
754 Steps 'c' and 'd' are needed because bison requires by default that the
755 files 'bison.simple' and 'bison.hairy' reside in some weird Unix directory,
756 '/usr/local/share/' I think.
757 So it is necessary to tell bison where those files are located if they
758 are not in such directory.
759 That is the function of the environment variables BISON_SIMPLE and BISON_HAIRY.
763 e) In the Visual C++ IDE click Tools, Options, select the Directory tab,
764 in 'Show directories for:' select 'Executable files', and in the directories
765 window add a new path: 'c:
768 Note that you can use any other path instead of 'c:
770 util', even the path where the Visual C++ tools are, probably: 'C:
774 Microsoft Visual Studio
779 So you don't have to execute step 'e' :)
783 Open 'sdcc.dsw' in Visual Studio, click 'build all', when it finishes copy
784 the executables from sdcc
788 bin, and you can compile using sdcc.
789 \layout Subsubsection
791 Windows Install Using Borland ......
799 Testing out the SDCC Compiler
802 The first thing you should do after installing your SDCC compiler is to
810 at the prompt, and the program should run and tell you the version.
811 If it doesn't run, or gives a message about not finding sdcc program, then
812 you need to check over your installation.
813 Make sure that the sdcc bin directory is in your executable search path
814 defined by the PATH environment setting (see the Trouble-shooting section
816 Make sure that the sdcc program is in the bin folder, if not perhaps something
817 did not install correctly.
823 SDCC binaries are commonly installed in a directory arrangement like this:
831 <lyxtabular version="3" rows="3" columns="2">
833 <column alignment="left" valignment="top" leftline="true" width="0(null)">
834 <column alignment="left" valignment="top" leftline="true" rightline="true" width="0(null)">
835 <row topline="true" bottomline="true">
836 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
846 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
853 Holds executables(sdcc, s51, aslink,
862 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
869 usr/local/share/sdcc/lib
872 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
885 <row topline="true" bottomline="true">
886 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
893 usr/local/share/sdcc/include
896 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
903 Holds common C header files
917 Make sure the compiler works on a very simple example.
918 Type in the following test.c program using your favorite editor:
949 Compile this using the following command:
958 If all goes well, the compiler will generate a test.asm and test.rel file.
959 Congratulations, you've just compiled your first program with SDCC.
960 We used the -c option to tell SDCC not to link the generated code, just
961 to keep things simple for this step.
969 The next step is to try it with the linker.
979 If all goes well the compiler will link with the libraries and produce
980 a test.ihx output file.
985 (no test.ihx, and the linker generates warnings), then the problem is most
986 likely that sdcc cannot find the
990 usr/local/share/sdcc/lib directory
994 (see the Install trouble-shooting section for suggestions).
1002 The final test is to ensure sdcc can use the
1006 header files and libraries.
1007 Edit test.c and change it to the following:
1027 strcpy(str1, "testing");
1036 Compile this by typing
1043 This should generate a test.ihx output file, and it should give no warnings
1044 such as not finding the string.h file.
1045 If it cannot find the string.h file, then the problem is that sdcc cannot
1046 find the /usr/local/share/sdcc/include directory
1050 (see the Install trouble-shooting section for suggestions).
1053 Install Trouble-shooting
1054 \layout Subsubsection
1056 SDCC does not build correctly.
1059 A thing to try is starting from scratch by unpacking the .tgz source package
1060 again in an empty directory.
1067 ./configure 2&>1 | tee configure.log
1079 make 2&>1 | tee make.log
1085 If anything goes wrong, you can review the log files to locate the problem.
1086 Or a relevant part of this can be attached to an email that could be helpful
1087 when requesting help from the mailing list.
1088 \layout Subsubsection
1091 \begin_inset Quotes sld
1095 \begin_inset Quotes srd
1102 \begin_inset Quotes sld
1106 \begin_inset Quotes srd
1109 command is a script that analyzes your system and performs some configuration
1110 to ensure the source package compiles on your system.
1111 It will take a few minutes to run, and will compile a few tests to determine
1112 what compiler features are installed.
1113 \layout Subsubsection
1116 \begin_inset Quotes sld
1120 \begin_inset Quotes srd
1126 This runs the GNU make tool, which automatically compiles all the source
1127 packages into the final installed binary executables.
1128 \layout Subsubsection
1131 \begin_inset Quotes sld
1135 \begin_inset Quotes erd
1141 This will install the compiler, other executables and libraries in to the
1142 appropriate system directories.
1143 The default is to copy the executables to /usr/local/bin and the libraries
1144 and header files to /usr/local/share/sdcc/lib and /usr/local/share/sdcc/include.
1145 On most systems you will need super-user privilages to do this.
1148 Advanced Install Options
1152 \begin_inset Quotes eld
1156 \begin_inset Quotes erd
1159 command has several options.
1160 The most commonly used option is --prefix=<directory name>, where <directory
1161 name> is the final location for the sdcc executables and libraries, (default
1162 location is /usr/local).
1163 The installation process will create the following directory structure
1164 under the <directory name> specified (if they do not already exist).
1169 bin/ - binary exectables (add to PATH environment variable)
1173 bin/share/sdcc/include/ - include header files
1177 bin/share/sdcc/lib/small/ - Object & library files for small model library
1179 bin/share/sdcc/lib/large/ - Object & library files for large model library
1181 bin/share/sdcc/lib/ds390/ - Object & library files for DS80C390 library
1183 bin/share/sdcc/lib/z80/ - Object & library files for Z80 library
1191 \begin_inset Quotes sld
1194 ./configure --prefix=/usr/local
1195 \begin_inset Quotes erd
1201 will configure the compiler to be installed in directory /usr/local.
1207 SDCC is not just a compiler, but a collection of tools by various developers.
1208 These include linkers, assemblers, simulators and other components.
1209 Here is a summary of some of the components.
1210 Note that the included simulator and assembler have separate documentation
1211 which you can find in the source package in their respective directories.
1212 As SDCC grows to include support for other processors, other packages from
1213 various developers are included and may have their own sets of documentation.
1217 You might want to look at the files which are installed in <installdir>.
1218 At the time of this writing, we find the following programs:
1222 In <installdir>/bin:
1225 sdcc - The compiler.
1228 sdcpp - The C preprocessor.
1231 asx8051 - The assembler for 8051 type processors.
1238 as-gbz80 - The Z80 and GameBoy Z80 assemblers.
1241 aslink -The linker for 8051 type processors.
1248 link-gbz80 - The Z80 and GameBoy Z80 linkers.
1251 s51 - The ucSim 8051 simulator.
1254 sdcdb - The source debugger.
1257 packihx - A tool to pack (compress) Intel hex files.
1260 In <installdir>/share/sdcc/include
1266 In <installdir>/share/sdcc/lib
1269 the sources of the runtime library and the subdirs small large and ds390
1270 with the precompiled relocatables.
1273 In <installdir>/share/sdcc/doc
1279 As development for other processors proceeds, this list will expand to include
1280 executables to support processors like AVR, PIC, etc.
1281 \layout Subsubsection
1286 This is the actual compiler, it in turn uses the c-preprocessor and invokes
1287 the assembler and linkage editor.
1288 \layout Subsubsection
1290 sdcpp - The C-Preprocessor)
1293 The preprocessor is a modified version of the GNU preprocessor.
1294 The C preprocessor is used to pull in #include sources, process #ifdef
1295 statements, #defines and so on.
1296 \layout Subsubsection
1298 asx8051, as-z80, as-gbz80, aslink, link-z80, link-gbz80 - The Assemblers
1302 This is retargettable assembler & linkage editor, it was developed by Alan
1304 John Hartman created the version for 8051, and I (Sandeep) have made some
1305 enhancements and bug fixes for it to work properly with the SDCC.
1306 \layout Subsubsection
1311 S51 is a freeware, opensource simulator developed by Daniel Drotos (
1312 \begin_inset LatexCommand \url{mailto:drdani@mazsola.iit.uni-miskolc.hu}
1317 The simulator is built as part of the build process.
1318 For more information visit Daniel's website at:
1319 \begin_inset LatexCommand \url{http://mazsola.iit.uni-miskolc.hu/~drdani/embedded/s51}
1324 It currently support the core mcs51, the Dallas DS80C390 and the Philips
1326 \layout Subsubsection
1328 sdcdb - Source Level Debugger
1334 <todo: is this thing alive?>
1341 Sdcdb is the companion source level debugger.
1342 The current version of the debugger uses Daniel's Simulator S51, but can
1343 be easily changed to use other simulators.
1350 \layout Subsubsection
1352 Single Source File Projects
1355 For single source file 8051 projects the process is very simple.
1356 Compile your programs with the following command
1359 "sdcc sourcefile.c".
1363 This will compile, assemble and link your source file.
1364 Output files are as follows
1368 sourcefile.asm - Assembler source file created by the compiler
1370 sourcefile.lst - Assembler listing file created by the Assembler
1372 sourcefile.rst - Assembler listing file updated with linkedit information,
1373 created by linkage editor
1375 sourcefile.sym - symbol listing for the sourcefile, created by the assembler
1377 sourcefile.rel - Object file created by the assembler, input to Linkage editor
1379 sourcefile.map - The memory map for the load module, created by the Linker
1381 sourcefile.ihx - The load module in Intel hex format (you can select the
1382 Motorola S19 format with --out-fmt-s19)
1384 sourcefile.cdb - An optional file (with --debug) containing debug information
1387 \layout Subsubsection
1389 Projects with Multiple Source Files
1392 SDCC can compile only ONE file at a time.
1393 Let us for example assume that you have a project containing the following
1398 foo1.c (contains some functions)
1400 foo2.c (contains some more functions)
1402 foomain.c (contains more functions and the function main)
1410 The first two files will need to be compiled separately with the commands:
1442 Then compile the source file containing the
1446 function and link the files together with the following command:
1454 foomain.c\SpecialChar ~
1455 foo1.rel\SpecialChar ~
1467 can be separately compiled as well:
1478 sdcc foomain.rel foo1.rel foo2.rel
1485 The file containing the
1500 file specified in the command line, since the linkage editor processes
1501 file in the order they are presented to it.
1502 \layout Subsubsection
1504 Projects with Additional Libraries
1507 Some reusable routines may be compiled into a library, see the documentation
1508 for the assembler and linkage editor (which are in <installdir>/share/sdcc/doc)
1514 Libraries created in this manner can be included in the command line.
1515 Make sure you include the -L <library-path> option to tell the linker where
1516 to look for these files if they are not in the current directory.
1517 Here is an example, assuming you have the source file
1529 (if that is not the same as your current project):
1536 sdcc foomain.c foolib.lib -L mylib
1547 must be an absolute path name.
1551 The most efficient way to use libraries is to keep seperate modules in seperate
1553 The lib file now should name all the modules.rel files.
1554 For an example see the standard library file
1558 in the directory <installdir>/share/lib/small.
1561 Command Line Options
1562 \layout Subsubsection
1564 Processor Selection Options
1566 \labelwidthstring 00.00.0000
1572 Generate code for the MCS51 (8051) family of processors.
1573 This is the default processor target.
1575 \labelwidthstring 00.00.0000
1581 Generate code for the DS80C390 processor.
1583 \labelwidthstring 00.00.0000
1589 Generate code for the Z80 family of processors.
1591 \labelwidthstring 00.00.0000
1597 Generate code for the GameBoy Z80 processor.
1599 \labelwidthstring 00.00.0000
1605 Generate code for the Atmel AVR processor (In development, not complete).
1607 \labelwidthstring 00.00.0000
1613 Generate code for the PIC 14-bit processors (In development, not complete).
1615 \labelwidthstring 00.00.0000
1621 Generate code for the Toshiba TLCS-900H processor (In development, not
1624 \labelwidthstring 00.00.0000
1630 Generate code for the Philips XA51 processor (In development, not complete).
1631 \layout Subsubsection
1633 Preprocessor Options
1635 \labelwidthstring 00.00.0000
1641 The additional location where the pre processor will look for <..h> or
1642 \begin_inset Quotes eld
1646 \begin_inset Quotes erd
1651 \labelwidthstring 00.00.0000
1657 Command line definition of macros.
1658 Passed to the pre processor.
1660 \labelwidthstring 00.00.0000
1666 Tell the preprocessor to output a rule suitable for make describing the
1667 dependencies of each object file.
1668 For each source file, the preprocessor outputs one make-rule whose target
1669 is the object file name for that source file and whose dependencies are
1670 all the files `#include'd in it.
1671 This rule may be a single line or may be continued with `
1673 '-newline if it is long.
1674 The list of rules is printed on standard output instead of the preprocessed
1678 \labelwidthstring 00.00.0000
1684 Tell the preprocessor not to discard comments.
1685 Used with the `-E' option.
1687 \labelwidthstring 00.00.0000
1698 Like `-M' but the output mentions only the user header files included with
1700 \begin_inset Quotes eld
1704 System header files included with `#include <file>' are omitted.
1706 \labelwidthstring 00.00.0000
1712 Assert the answer answer for question, in case it is tested with a preprocessor
1713 conditional such as `#if #question(answer)'.
1714 `-A-' disables the standard assertions that normally describe the target
1717 \labelwidthstring 00.00.0000
1723 (answer) Assert the answer answer for question, in case it is tested with
1724 a preprocessor conditional such as `#if #question(answer)'.
1725 `-A-' disables the standard assertions that normally describe the target
1728 \labelwidthstring 00.00.0000
1734 Undefine macro macro.
1735 `-U' options are evaluated after all `-D' options, but before any `-include'
1736 and `-imacros' options.
1738 \labelwidthstring 00.00.0000
1744 Tell the preprocessor to output only a list of the macro definitions that
1745 are in effect at the end of preprocessing.
1746 Used with the `-E' option.
1748 \labelwidthstring 00.00.0000
1754 Tell the preprocessor to pass all macro definitions into the output, in
1755 their proper sequence in the rest of the output.
1757 \labelwidthstring 00.00.0000
1768 Like `-dD' except that the macro arguments and contents are omitted.
1769 Only `#define name' is included in the output.
1770 \layout Subsubsection
1774 \labelwidthstring 00.00.0000
1781 the output path resp.
1782 file where everything will be placed
1784 \labelwidthstring 00.00.0000
1794 <absolute path to additional libraries> This option is passed to the linkage
1795 editor's additional libraries search path.
1796 The path name must be absolute.
1797 Additional library files may be specified in the command line.
1798 See section Compiling programs for more details.
1800 \labelwidthstring 00.00.0000
1806 <Value> The start location of the external ram, default value is 0.
1807 The value entered can be in Hexadecimal or Decimal format, e.g.: --xram-loc
1808 0x8000 or --xram-loc 32768.
1810 \labelwidthstring 00.00.0000
1816 <Value> The start location of the code segment, default value 0.
1817 Note when this option is used the interrupt vector table is also relocated
1818 to the given address.
1819 The value entered can be in Hexadecimal or Decimal format, e.g.: --code-loc
1820 0x8000 or --code-loc 32768.
1822 \labelwidthstring 00.00.0000
1828 <Value> By default the stack is placed after the data segment.
1829 Using this option the stack can be placed anywhere in the internal memory
1831 The value entered can be in Hexadecimal or Decimal format, e.g.
1832 --stack-loc 0x20 or --stack-loc 32.
1833 Since the sp register is incremented before a push or call, the initial
1834 sp will be set to one byte prior the provided value.
1835 The provided value should not overlap any other memory areas such as used
1836 register banks or the data segment and with enough space for the current
1839 \labelwidthstring 00.00.0000
1845 <Value> The start location of the internal ram data segment, the default
1846 value is 0x30.The value entered can be in Hexadecimal or Decimal format,
1848 --data-loc 0x20 or --data-loc 32.
1850 \labelwidthstring 00.00.0000
1856 <Value> The start location of the indirectly addressable internal ram, default
1858 The value entered can be in Hexadecimal or Decimal format, eg.
1859 --idata-loc 0x88 or --idata-loc 136.
1861 \labelwidthstring 00.00.0000
1870 The linker output (final object code) is in Intel Hex format.
1871 (This is the default option).
1873 \labelwidthstring 00.00.0000
1882 The linker output (final object code) is in Motorola S19 format.
1883 \layout Subsubsection
1887 \labelwidthstring 00.00.0000
1893 Generate code for Large model programs see section Memory Models for more
1895 If this option is used all source files in the project should be compiled
1897 In addition the standard library routines are compiled with small model,
1898 they will need to be recompiled.
1900 \labelwidthstring 00.00.0000
1911 Generate code for Small Model programs see section Memory Models for more
1913 This is the default model.
1914 \layout Subsubsection
1918 \labelwidthstring 00.00.0000
1929 Generate 24-bit flat mode code.
1930 This is the one and only that the ds390 code generator supports right now
1931 and is default when using
1936 See section Memory Models for more details.
1938 \labelwidthstring 00.00.0000
1944 Generate code for the 10 bit stack mode of the Dallas DS80C390 part.
1945 This is the one and only that the ds390 code generator supports right now
1946 and is default when using
1951 In this mode, the stack is located in the lower 1K of the internal RAM,
1952 which is mapped to 0x400000.
1953 Note that the support is incomplete, since it still uses a single byte
1954 as the stack pointer.
1955 This means that only the lower 256 bytes of the potential 1K stack space
1956 will actually be used.
1957 However, this does allow you to reclaim the precious 256 bytes of low RAM
1958 for use for the DATA and IDATA segments.
1959 The compiler will not generate any code to put the processor into 10 bit
1961 It is important to ensure that the processor is in this mode before calling
1962 any re-entrant functions compiled with this option.
1963 In principle, this should work with the
1967 option, but that has not been tested.
1968 It is incompatible with the
1973 It also only makes sense if the processor is in 24 bit contiguous addressing
1976 --model-flat24 option
1979 \layout Subsubsection
1981 Optimization Options
1983 \labelwidthstring 00.00.0000
1989 Will not do global subexpression elimination, this option may be used when
1990 the compiler creates undesirably large stack/data spaces to store compiler
1992 A warning message will be generated when this happens and the compiler
1993 will indicate the number of extra bytes it allocated.
1994 It recommended that this option NOT be used, #pragma\SpecialChar ~
1996 to turn off global subexpression elimination for a given function only.
1998 \labelwidthstring 00.00.0000
2004 Will not do loop invariant optimizations, this may be turned off for reasons
2005 explained for the previous option.
2006 For more details of loop optimizations performed see section Loop Invariants.It
2007 recommended that this option NOT be used, #pragma\SpecialChar ~
2008 NOINVARIANT can be used
2009 to turn off invariant optimizations for a given function only.
2011 \labelwidthstring 00.00.0000
2017 Will not do loop induction optimizations, see section strength reduction
2018 for more details.It is recommended that this option is NOT used, #pragma\SpecialChar ~
2020 ION can be used to turn off induction optimizations for a given function
2023 \labelwidthstring 00.00.0000
2034 Will not generate boundary condition check when switch statements are implement
2035 ed using jump-tables.
2036 See section Switch Statements for more details.
2037 It is recommended that this option is NOT used, #pragma\SpecialChar ~
2039 used to turn off boundary checking for jump tables for a given function
2042 \labelwidthstring 00.00.0000
2051 Will not do loop reversal optimization.
2053 \labelwidthstring 00.00.0000
2059 This will disable the memcpy of initialized data in far space from code
2061 \layout Subsubsection
2065 \labelwidthstring 00.00.0000
2072 will compile and assemble the source, but will not call the linkage editor.
2074 \labelwidthstring 00.00.0000
2080 Run only the C preprocessor.
2081 Preprocess all the C source files specified and output the results to standard
2084 \labelwidthstring 00.00.0000
2095 All functions in the source file will be compiled as
2100 the parameters and local variables will be allocated on the stack.
2101 see section Parameters and Local Variables for more details.
2102 If this option is used all source files in the project should be compiled
2106 \labelwidthstring 00.00.0000
2112 Uses a pseudo stack in the first 256 bytes in the external ram for allocating
2113 variables and passing parameters.
2114 See section on external stack for more details.
2116 \labelwidthstring 00.00.0000
2120 --callee-saves function1[,function2][,function3]....
2123 The compiler by default uses a caller saves convention for register saving
2124 across function calls, however this can cause unneccessary register pushing
2125 & popping when calling small functions from larger functions.
2126 This option can be used to switch the register saving convention for the
2127 function names specified.
2128 The compiler will not save registers when calling these functions, no extra
2129 code will be generated at the entry & exit for these functions to save
2130 & restore the registers used by these functions, this can SUBSTANTIALLY
2131 reduce code & improve run time performance of the generated code.
2132 In the future the compiler (with interprocedural analysis) will be able
2133 to determine the appropriate scheme to use for each function call.
2134 DO NOT use this option for built-in functions such as _muluint..., if this
2135 option is used for a library function the appropriate library function
2136 needs to be recompiled with the same option.
2137 If the project consists of multiple source files then all the source file
2138 should be compiled with the same --callee-saves option string.
2139 Also see #pragma\SpecialChar ~
2142 \labelwidthstring 00.00.0000
2151 When this option is used the compiler will generate debug information, that
2152 can be used with the SDCDB.
2153 The debug information is collected in a file with .cdb extension.
2154 For more information see documentation for SDCDB.
2156 \labelwidthstring 00.00.0000
2162 <filename> This option can be used to use additional rules to be used by
2163 the peep hole optimizer.
2164 See section Peep Hole optimizations for details on how to write these rules.
2166 \labelwidthstring 00.00.0000
2177 Stop after the stage of compilation proper; do not assemble.
2178 The output is an assembler code file for the input file specified.
2180 \labelwidthstring 00.00.0000
2184 -Wa_asmOption[,asmOption]
2187 Pass the asmOption to the assembler.
2189 \labelwidthstring 00.00.0000
2193 -Wl_linkOption[,linkOption]
2196 Pass the linkOption to the linker.
2198 \labelwidthstring 00.00.0000
2207 Integer (16 bit) and long (32 bit) libraries have been compiled as reentrant.
2208 Note by default these libraries are compiled as non-reentrant.
2209 See section Installation for more details.
2211 \labelwidthstring 00.00.0000
2220 This option will cause the compiler to generate an information message for
2221 each function in the source file.
2222 The message contains some
2226 information about the function.
2227 The number of edges and nodes the compiler detected in the control flow
2228 graph of the function, and most importantly the
2230 cyclomatic complexity
2232 see section on Cyclomatic Complexity for more details.
2234 \labelwidthstring 00.00.0000
2243 Floating point library is compiled as reentrant.See section Installation
2246 \labelwidthstring 00.00.0000
2252 The compiler will not overlay parameters and local variables of any function,
2253 see section Parameters and local variables for more details.
2255 \labelwidthstring 00.00.0000
2261 This option can be used when the code generated is called by a monitor
2263 The compiler will generate a 'ret' upon return from the 'main' function.
2264 The default option is to lock up i.e.
2267 \labelwidthstring 00.00.0000
2273 Disable peep-hole optimization.
2275 \labelwidthstring 00.00.0000
2281 Pass the inline assembler code through the peep hole optimizer.
2282 This can cause unexpected changes to inline assembler code, please go through
2283 the peephole optimizer rules defined in the source file tree '<target>/peeph.def
2284 ' before using this option.
2286 \labelwidthstring 00.00.0000
2292 <Value> Causes the linker to check if the internal ram usage is within limits
2295 \labelwidthstring 00.00.0000
2301 <Value> Causes the linker to check if the external ram usage is within limits
2304 \labelwidthstring 00.00.0000
2310 <Value> Causes the linker to check if the code usage is within limits of
2313 \labelwidthstring 00.00.0000
2319 This will prevent the compiler from passing on the default include path
2320 to the preprocessor.
2322 \labelwidthstring 00.00.0000
2328 This will prevent the compiler from passing on the default library path
2331 \labelwidthstring 00.00.0000
2337 Shows the various actions the compiler is performing.
2339 \labelwidthstring 00.00.0000
2345 Shows the actual commands the compiler is executing.
2346 \layout Subsubsection
2348 Intermediate Dump Options
2351 The following options are provided for the purpose of retargetting and debugging
2353 These provided a means to dump the intermediate code (iCode) generated
2354 by the compiler in human readable form at various stages of the compilation
2358 \labelwidthstring 00.00.0000
2364 This option will cause the compiler to dump the intermediate code into
2367 <source filename>.dumpraw
2369 just after the intermediate code has been generated for a function, i.e.
2370 before any optimizations are done.
2371 The basic blocks at this stage ordered in the depth first number, so they
2372 may not be in sequence of execution.
2374 \labelwidthstring 00.00.0000
2380 Will create a dump of iCode's, after global subexpression elimination,
2383 <source filename>.dumpgcse.
2385 \labelwidthstring 00.00.0000
2391 Will create a dump of iCode's, after deadcode elimination, into a file
2394 <source filename>.dumpdeadcode.
2396 \labelwidthstring 00.00.0000
2405 Will create a dump of iCode's, after loop optimizations, into a file named
2408 <source filename>.dumploop.
2410 \labelwidthstring 00.00.0000
2419 Will create a dump of iCode's, after live range analysis, into a file named
2422 <source filename>.dumprange.
2424 \labelwidthstring 00.00.0000
2430 Will dump the life ranges for all symbols.
2432 \labelwidthstring 00.00.0000
2441 Will create a dump of iCode's, after register assignment, into a file named
2444 <source filename>.dumprassgn.
2446 \labelwidthstring 00.00.0000
2452 Will create a dump of the live ranges of iTemp's
2454 \labelwidthstring 00.00.0000
2465 Will cause all the above mentioned dumps to be created.
2468 MCS51/DS390 Storage Class Language Extensions
2471 In addition to the ANSI storage classes SDCC allows the following MCS51
2472 specific storage classes.
2473 \layout Subsubsection
2478 Variables declared with this storage class will be placed in the extern
2484 storage class for Large Memory model, e.g.:
2490 xdata unsigned char xduc;
2491 \layout Subsubsection
2500 storage class for Small Memory model.
2501 Variables declared with this storage class will be allocated in the internal
2509 \layout Subsubsection
2514 Variables declared with this storage class will be allocated into the indirectly
2515 addressable portion of the internal ram of a 8051, e.g.:
2522 \layout Subsubsection
2527 This is a data-type and a storage class specifier.
2528 When a variable is declared as a bit, it is allocated into the bit addressable
2529 memory of 8051, e.g.:
2536 \layout Subsubsection
2541 Like the bit keyword,
2545 signifies both a data-type and storage class, they are used to describe
2546 the special function registers and special bit variables of a 8051, eg:
2552 sfr at 0x80 P0; /* special function register P0 at location 0x80 */
2554 sbit at 0xd7 CY; /* CY (Carry Flag) */
2560 SDCC allows (via language extensions) pointers to explicitly point to any
2561 of the memory spaces of the 8051.
2562 In addition to the explicit pointers, the compiler uses (by default) generic
2563 pointers which can be used to point to any of the memory spaces.
2567 Pointer declaration examples:
2576 /* pointer physically in xternal ram pointing to object in internal ram
2579 data unsigned char * xdata p;
2583 /* pointer physically in code rom pointing to data in xdata space */
2585 xdata unsigned char * code p;
2589 /* pointer physically in code space pointing to data in code space */
2591 code unsigned char * code p;
2595 /* the folowing is a generic pointer physically located in xdata space */
2606 Well you get the idea.
2611 All unqualified pointers are treated as 3-byte (4-byte for the ds390)
2624 The highest order byte of the
2628 pointers contains the data space information.
2629 Assembler support routines are called whenever data is stored or retrieved
2635 These are useful for developing reusable library routines.
2636 Explicitly specifying the pointer type will generate the most efficient
2640 Parameters & Local Variables
2643 Automatic (local) variables and parameters to functions can either be placed
2644 on the stack or in data-space.
2645 The default action of the compiler is to place these variables in the internal
2646 RAM (for small model) or external RAM (for large model).
2647 This in fact makes them
2651 so by default functions are non-reentrant.
2655 They can be placed on the stack either by using the
2659 option or by using the
2663 keyword in the function declaration, e.g.:
2672 unsigned char foo(char i) reentrant
2685 Since stack space on 8051 is limited, the
2693 option should be used sparingly.
2694 Note that the reentrant keyword just means that the parameters & local
2695 variables will be allocated to the stack, it
2699 mean that the function is register bank independent.
2703 Local variables can be assigned storage classes and absolute addresses,
2710 unsigned char foo() {
2716 xdata unsigned char i;
2728 data at 0x31 unsiged char j;
2743 In the above example the variable
2747 will be allocated in the external ram,
2751 in bit addressable space and
2760 or when a function is declared as
2764 this should only be done for static variables.
2767 Parameters however are not allowed any storage class, (storage classes for
2768 parameters will be ignored), their allocation is governed by the memory
2769 model in use, and the reentrancy options.
2775 For non-reentrant functions SDCC will try to reduce internal ram space usage
2776 by overlaying parameters and local variables of a function (if possible).
2777 Parameters and local variables of a function will be allocated to an overlayabl
2778 e segment if the function has
2780 no other function calls and the function is non-reentrant and the memory
2784 If an explicit storage class is specified for a local variable, it will
2788 Note that the compiler (not the linkage editor) makes the decision for overlayin
2790 Functions that are called from an interrupt service routine should be preceded
2791 by a #pragma\SpecialChar ~
2792 NOOVERLAY if they are not reentrant.
2795 Also note that the compiler does not do any processing of inline assembler
2796 code, so the compiler might incorrectly assign local variables and parameters
2797 of a function into the overlay segment if the inline assembler code calls
2798 other c-functions that might use the overlay.
2799 In that case the #pragma\SpecialChar ~
2800 NOOVERLAY should be used.
2803 Parameters and Local variables of functions that contain 16 or 32 bit multiplica
2804 tion or division will NOT be overlayed since these are implemented using
2805 external functions, e.g.:
2815 void set_error(unsigned char errcd)
2831 void some_isr () interrupt 2 using 1
2860 In the above example the parameter
2868 would be assigned to the overlayable segment if the #pragma\SpecialChar ~
2870 not present, this could cause unpredictable runtime behavior when called
2872 The #pragma\SpecialChar ~
2873 NOOVERLAY ensures that the parameters and local variables for
2874 the function are NOT overlayed.
2877 Interrupt Service Routines
2880 SDCC allows interrupt service routines to be coded in C, with some extended
2887 void timer_isr (void) interrupt 2 using 1
2900 The number following the
2904 keyword is the interrupt number this routine will service.
2905 The compiler will insert a call to this routine in the interrupt vector
2906 table for the interrupt number specified.
2911 keyword is used to tell the compiler to use the specified register bank
2912 (8051 specific) when generating code for this function.
2913 Note that when some function is called from an interrupt service routine
2914 it should be preceded by a #pragma\SpecialChar ~
2915 NOOVERLAY if it is not reentrant.
2916 A special note here, int (16 bit) and long (32 bit) integer division, multiplic
2917 ation & modulus operations are implemented using external support routines
2918 developed in ANSI-C, if an interrupt service routine needs to do any of
2919 these operations then the support routines (as mentioned in a following
2920 section) will have to be recompiled using the
2924 option and the source file will need to be compiled using the
2931 If you have multiple source files in your project, interrupt service routines
2932 can be present in any of them, but a prototype of the isr MUST be present
2933 or included in the file that contains the function
2940 Interrupt Numbers and the corresponding address & descriptions for the Standard
2941 8051 are listed below.
2942 SDCC will automatically adjust the interrupt vector table to the maximum
2943 interrupt number specified.
2949 \begin_inset Tabular
2950 <lyxtabular version="3" rows="6" columns="3">
2952 <column alignment="center" valignment="top" leftline="true" width="0(null)">
2953 <column alignment="center" valignment="top" leftline="true" width="0(null)">
2954 <column alignment="center" valignment="top" leftline="true" rightline="true" width="0(null)">
2955 <row topline="true" bottomline="true">
2956 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
2964 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
2972 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
2981 <row topline="true">
2982 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
2990 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
2998 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3007 <row topline="true">
3008 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3016 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3024 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3033 <row topline="true">
3034 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3042 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3050 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3059 <row topline="true">
3060 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3068 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3076 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3085 <row topline="true" bottomline="true">
3086 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3094 <cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
3102 <cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
3119 If the interrupt service routine is defined without
3123 a register bank or with register bank 0 (using 0), the compiler will save
3124 the registers used by itself on the stack upon entry and restore them at
3125 exit, however if such an interrupt service routine calls another function
3126 then the entire register bank will be saved on the stack.
3127 This scheme may be advantageous for small interrupt service routines which
3128 have low register usage.
3131 If the interrupt service routine is defined to be using a specific register
3136 are save and restored, if such an interrupt service routine calls another
3137 function (using another register bank) then the entire register bank of
3138 the called function will be saved on the stack.
3139 This scheme is recommended for larger interrupt service routines.
3142 Calling other functions from an interrupt service routine is not recommended,
3143 avoid it if possible.
3147 Also see the _naked modifier.
3155 <TODO: this isn't implemented at all!>
3161 A special keyword may be associated with a function declaring it as
3166 SDCC will generate code to disable all interrupts upon entry to a critical
3167 function and enable them back before returning.
3168 Note that nesting critical functions may cause unpredictable results.
3193 The critical attribute maybe used with other attributes like
3201 A special keyword may be associated with a function declaring it as
3210 function modifier attribute prevents the compiler from generating prologue
3211 and epilogue code for that function.
3212 This means that the user is entirely responsible for such things as saving
3213 any registers that may need to be preserved, selecting the proper register
3214 bank, generating the
3218 instruction at the end, etc.
3219 Practically, this means that the contents of the function must be written
3220 in inline assembler.
3221 This is particularly useful for interrupt functions, which can have a large
3222 (and often unnecessary) prologue/epilogue.
3223 For example, compare the code generated by these two functions:
3229 data unsigned char counter;
3231 void simpleInterrupt(void) interrupt 1
3245 void nakedInterrupt(void) interrupt 2 _naked
3278 ; MUST explicitly include ret in _naked function.
3292 For an 8051 target, the generated simpleInterrupt looks like:
3437 whereas nakedInterrupt looks like:
3462 ; MUST explicitly include ret(i) in _naked function.
3468 While there is nothing preventing you from writing C code inside a _naked
3469 function, there are many ways to shoot yourself in the foot doing this,
3470 and is is recommended that you stick to inline assembler.
3473 Functions using private banks
3480 attribute (which tells the compiler to use a register bank other than the
3481 default bank zero) should only be applied to
3485 functions (see note 1 below).
3486 This will in most circumstances make the generated ISR code more efficient
3487 since it will not have to save registers on the stack.
3494 attribute will have no effect on the generated code for a
3498 function (but may occasionally be useful anyway
3504 possible exception: if a function is called ONLY from 'interrupt' functions
3505 using a particular bank, it can be declared with the same 'using' attribute
3506 as the calling 'interrupt' functions.
3507 For instance, if you have several ISRs using bank one, and all of them
3508 call memcpy(), it might make sense to create a specialized version of memcpy()
3509 'using 1', since this would prevent the ISR from having to save bank zero
3510 to the stack on entry and switch to bank zero before calling the function
3517 (pending: I don't think this has been done yet)
3524 function using a non-zero bank will assume that it can trash that register
3525 bank, and will not save it.
3526 Since high-priority interrupts can interrupt low-priority ones on the 8051
3527 and friends, this means that if a high-priority ISR
3531 a particular bank occurs while processing a low-priority ISR
3535 the same bank, terrible and bad things can happen.
3536 To prevent this, no single register bank should be
3540 by both a high priority and a low priority ISR.
3541 This is probably most easily done by having all high priority ISRs use
3542 one bank and all low priority ISRs use another.
3543 If you have an ISR which can change priority at runtime, you're on your
3544 own: I suggest using the default bank zero and taking the small performance
3548 It is most efficient if your ISR calls no other functions.
3549 If your ISR must call other functions, it is most efficient if those functions
3550 use the same bank as the ISR (see note 1 below); the next best is if the
3551 called functions use bank zero.
3552 It is very inefficient to call a function using a different, non-zero bank
3560 Data items can be assigned an absolute address with the
3564 keyword, in addition to a storage class, e.g.:
3570 xdata at 0x8000 unsigned char PORTA_8255 ;
3576 In the above example the PORTA_8255 will be allocated to the location 0x8000
3577 of the external ram.
3578 Note that this feature is provided to give the programmer access to
3582 devices attached to the controller.
3583 The compiler does not actually reserve any space for variables declared
3584 in this way (they are implemented with an equate in the assembler).
3585 Thus it is left to the programmer to make sure there are no overlaps with
3586 other variables that are declared without the absolute address.
3587 The assembler listing file (.lst) and the linker output files (.rst) and
3588 (.map) are a good places to look for such overlaps.
3592 Absolute address can be specified for variables in all storage classes,
3605 The above example will allocate the variable at offset 0x02 in the bit-addressab
3607 There is no real advantage to assigning absolute addresses to variables
3608 in this manner, unless you want strict control over all the variables allocated.
3614 The compiler inserts a call to the C routine
3616 _sdcc__external__startup()
3621 at the start of the CODE area.
3622 This routine is in the runtime library.
3623 By default this routine returns 0, if this routine returns a non-zero value,
3624 the static & global variable initialization will be skipped and the function
3625 main will be invoked Other wise static & global variables will be initialized
3626 before the function main is invoked.
3629 _sdcc__external__startup()
3631 routine to your program to override the default if you need to setup hardware
3632 or perform some other critical operation prior to static & global variable
3636 Inline Assembler Code
3639 SDCC allows the use of in-line assembler with a few restriction as regards
3641 All labels defined within inline assembler code
3649 where nnnn is a number less than 100 (which implies a limit of utmost 100
3650 inline assembler labels
3658 It is strongly recommended that each assembly instruction (including labels)
3659 be placed in a separate line (as the example shows).
3664 command line option is used, the inline assembler code will be passed through
3665 the peephole optimizer.
3666 This might cause some unexpected changes in the inline assembler code.
3667 Please go throught the peephole optimizer rules defined in file
3671 carefully before using this option.
3711 The inline assembler code can contain any valid code understood by the assembler
3712 , this includes any assembler directives and comment lines.
3713 The compiler does not do any validation of the code within the
3723 Inline assembler code cannot reference any C-Labels, however it can reference
3724 labels defined by the inline assembler, e.g.:
3750 ; some assembler code
3770 /* some more c code */
3772 clabel:\SpecialChar ~
3774 /* inline assembler cannot reference this label */
3786 $0003: ;label (can be reference by inline assembler only)
3798 /* some more c code */
3806 In other words inline assembly code can access labels defined in inline
3807 assembly within the scope of the funtion.
3811 The same goes the other way, ie.
3812 labels defines in inline assembly CANNOT be accessed by C statements.
3815 int(16 bit) and long (32 bit) Support
3818 For signed & unsigned int (16 bit) and long (32 bit) variables, division,
3819 multiplication and modulus operations are implemented by support routines.
3820 These support routines are all developed in ANSI-C to facilitate porting
3821 to other MCUs, although some model specific assembler optimations are used.
3822 The following files contain the described routine, all of them can be found
3823 in <installdir>/share/sdcc/lib.
3829 <pending: tabularise this>
3835 _mulsint.c - signed 16 bit multiplication (calls _muluint)
3837 _muluint.c - unsigned 16 bit multiplication
3839 _divsint.c - signed 16 bit division (calls _divuint)
3841 _divuint.c - unsigned 16 bit division
3843 _modsint.c - signed 16 bit modulus (call _moduint)
3845 _moduint.c - unsigned 16 bit modulus
3847 _mulslong.c - signed 32 bit multiplication (calls _mululong)
3849 _mululong.c - unsigned32 bit multiplication
3851 _divslong.c - signed 32 division (calls _divulong)
3853 _divulong.c - unsigned 32 division
3855 _modslong.c - signed 32 bit modulus (calls _modulong)
3857 _modulong.c - unsigned 32 bit modulus
3865 Since they are compiled as
3869 , interrupt service routines should not do any of the above operations.
3870 If this is unavoidable then the above routines will need to be compiled
3875 option, after which the source program will have to be compiled with
3882 Floating Point Support
3885 SDCC supports IEEE (single precision 4bytes) floating point numbers.The floating
3886 point support routines are derived from gcc's floatlib.c and consists of
3887 the following routines:
3893 <pending: tabularise this>
3899 _fsadd.c - add floating point numbers
3901 _fssub.c - subtract floating point numbers
3903 _fsdiv.c - divide floating point numbers
3905 _fsmul.c - multiply floating point numbers
3907 _fs2uchar.c - convert floating point to unsigned char
3909 _fs2char.c - convert floating point to signed char
3911 _fs2uint.c - convert floating point to unsigned int
3913 _fs2int.c - convert floating point to signed int
3915 _fs2ulong.c - convert floating point to unsigned long
3917 _fs2long.c - convert floating point to signed long
3919 _uchar2fs.c - convert unsigned char to floating point
3921 _char2fs.c - convert char to floating point number
3923 _uint2fs.c - convert unsigned int to floating point
3925 _int2fs.c - convert int to floating point numbers
3927 _ulong2fs.c - convert unsigned long to floating point number
3929 _long2fs.c - convert long to floating point number
3937 Note if all these routines are used simultaneously the data space might
3939 For serious floating point usage it is strongly recommended that the large
3946 SDCC allows two memory models for MCS51 code, small and large.
3947 Modules compiled with different memory models should
3951 be combined together or the results would be unpredictable.
3952 The library routines supplied with the compiler are compiled as both small
3954 The compiled library modules are contained in seperate directories as small
3955 and large so that you can link to either set.
3959 When the large model is used all variables declared without a storage class
3960 will be allocated into the external ram, this includes all parameters and
3961 local variables (for non-reentrant functions).
3962 When the small model is used variables without storage class are allocated
3963 in the internal ram.
3966 Judicious usage of the processor specific storage classes and the 'reentrant'
3967 function type will yield much more efficient code, than using the large
3969 Several optimizations are disabled when the program is compiled using the
3970 large model, it is therefore strongly recommdended that the small model
3971 be used unless absolutely required.
3977 The only model supported is Flat 24.
3978 This generates code for the 24 bit contiguous addressing mode of the Dallas
3980 In this mode, up to four meg of external RAM or code space can be directly
3982 See the data sheets at www.dalsemi.com for further information on this part.
3986 In older versions of the compiler, this option was used with the MCS51 code
3992 Now, however, the '390 has it's own code generator, selected by the
4001 Note that the compiler does not generate any code to place the processor
4002 into 24 bitmode (although
4006 in the ds390 libraries will do that for you).
4011 , the boot loader or similar code must ensure that the processor is in 24
4012 bit contiguous addressing mode before calling the SDCC startup code.
4020 option, variables will by default be placed into the XDATA segment.
4025 Segments may be placed anywhere in the 4 meg address space using the usual
4027 Note that if any segments are located above 64K, the -r flag must be passed
4028 to the linker to generate the proper segment relocations, and the Intel
4029 HEX output format must be used.
4030 The -r flag can be passed to the linker by using the option
4034 on the sdcc command line.
4035 However, currently the linker can not handle code segments > 64k.
4038 Defines Created by the Compiler
4041 The compiler creates the following #defines.
4044 SDCC - this Symbol is always defined.
4047 SDCC_mcs51 or SDCC_ds390 or SDCC_z80, etc - depending on the model used
4051 __mcs51 or __ds390 or __z80, etc - depending on the model used (e.g.
4055 SDCC_STACK_AUTO - this symbol is defined when
4062 SDCC_MODEL_SMALL - when
4069 SDCC_MODEL_LARGE - when
4076 SDCC_USE_XSTACK - when
4083 SDCC_STACK_TENBIT - when
4090 SDCC_MODEL_FLAT24 - when
4103 SDCC performs a host of standard optimizations in addition to some MCU specific
4106 \layout Subsubsection
4108 Sub-expression Elimination
4111 The compiler does local and global common subexpression elimination, e.g.:
4126 will be translated to
4142 Some subexpressions are not as obvious as the above example, e.g.:
4156 In this case the address arithmetic a->b[i] will be computed only once;
4157 the equivalent code in C would be.
4173 The compiler will try to keep these temporary variables in registers.
4174 \layout Subsubsection
4176 Dead-Code Elimination
4191 i = 1; \SpecialChar ~
4196 global = 1;\SpecialChar ~
4209 global = 3;\SpecialChar ~
4224 int global; void f ()
4237 \layout Subsubsection
4298 Note: the dead stores created by this copy propagation will be eliminated
4299 by dead-code elimination.
4300 \layout Subsubsection
4305 Two types of loop optimizations are done by SDCC loop invariant lifting
4306 and strength reduction of loop induction variables.
4307 In addition to the strength reduction the optimizer marks the induction
4308 variables and the register allocator tries to keep the induction variables
4309 in registers for the duration of the loop.
4310 Because of this preference of the register allocator, loop induction optimizati
4311 on causes an increase in register pressure, which may cause unwanted spilling
4312 of other temporary variables into the stack / data space.
4313 The compiler will generate a warning message when it is forced to allocate
4314 extra space either on the stack or data space.
4315 If this extra space allocation is undesirable then induction optimization
4316 can be eliminated either for the entire source file (with --noinduction
4317 option) or for a given function only using #pragma\SpecialChar ~
4328 for (i = 0 ; i < 100 ; i ++)
4346 for (i = 0; i < 100; i++)
4356 As mentioned previously some loop invariants are not as apparent, all static
4357 address computations are also moved out of the loop.
4361 Strength Reduction, this optimization substitutes an expression by a cheaper
4368 for (i=0;i < 100; i++)
4388 for (i=0;i< 100;i++) {
4392 ar[itemp1] = itemp2;
4408 The more expensive multiplication is changed to a less expensive addition.
4409 \layout Subsubsection
4414 This optimization is done to reduce the overhead of checking loop boundaries
4415 for every iteration.
4416 Some simple loops can be reversed and implemented using a
4417 \begin_inset Quotes eld
4420 decrement and jump if not zero
4421 \begin_inset Quotes erd
4425 SDCC checks for the following criterion to determine if a loop is reversible
4426 (note: more sophisticated compilers use data-dependency analysis to make
4427 this determination, SDCC uses a more simple minded analysis).
4430 The 'for' loop is of the form
4436 for (<symbol> = <expression> ; <sym> [< | <=] <expression> ; [<sym>++ |
4446 The <for body> does not contain
4447 \begin_inset Quotes eld
4451 \begin_inset Quotes erd
4455 \begin_inset Quotes erd
4461 All goto's are contained within the loop.
4464 No function calls within the loop.
4467 The loop control variable <sym> is not assigned any value within the loop
4470 The loop control variable does NOT participate in any arithmetic operation
4474 There are NO switch statements in the loop.
4475 \layout Subsubsection
4477 Algebraic Simplifications
4480 SDCC does numerous algebraic simplifications, the following is a small sub-set
4481 of these optimizations.
4487 i = j + 0 ; /* changed to */ i = j;
4489 i /= 2; /* changed to */ i >>= 1;
4491 i = j - j ; /* changed to */ i = 0;
4493 i = j / 1 ; /* changed to */ i = j;
4499 Note the subexpressions given above are generally introduced by macro expansions
4500 or as a result of copy/constant propagation.
4501 \layout Subsubsection
4506 SDCC changes switch statements to jump tables when the following conditions
4511 The case labels are in numerical sequence, the labels need not be in order,
4512 and the starting number need not be one or zero.
4518 switch(i) {\SpecialChar ~
4625 Both the above switch statements will be implemented using a jump-table.
4628 The number of case labels is at least three, since it takes two conditional
4629 statements to handle the boundary conditions.
4632 The number of case labels is less than 84, since each label takes 3 bytes
4633 and a jump-table can be utmost 256 bytes long.
4637 Switch statements which have gaps in the numeric sequence or those that
4638 have more that 84 case labels can be split into more than one switch statement
4639 for efficient code generation, e.g.:
4677 If the above switch statement is broken down into two switch statements
4711 case 9: \SpecialChar ~
4721 case 12:\SpecialChar ~
4731 then both the switch statements will be implemented using jump-tables whereas
4732 the unmodified switch statement will not be.
4733 \layout Subsubsection
4735 Bit-shifting Operations.
4738 Bit shifting is one of the most frequently used operation in embedded programmin
4740 SDCC tries to implement bit-shift operations in the most efficient way
4760 generates the following code:
4778 In general SDCC will never setup a loop if the shift count is known.
4818 Note that SDCC stores numbers in little-endian format (i.e.
4819 lowest order first).
4820 \layout Subsubsection
4825 A special case of the bit-shift operation is bit rotation, SDCC recognizes
4826 the following expression to be a left bit-rotation:
4837 i = ((i << 1) | (i >> 7));
4845 will generate the following code:
4861 SDCC uses pattern matching on the parse tree to determine this operation.Variatio
4862 ns of this case will also be recognized as bit-rotation, i.e.:
4868 i = ((i >> 7) | (i << 1)); /* left-bit rotation */
4869 \layout Subsubsection
4874 It is frequently required to obtain the highest order bit of an integral
4875 type (long, int, short or char types).
4876 SDCC recognizes the following expression to yield the highest order bit
4877 and generates optimized code for it, e.g.:
4898 hob = (gint >> 15) & 1;
4911 will generate the following code:
4950 000A E5*01\SpecialChar ~
4978 000C 33\SpecialChar ~
5009 000D E4\SpecialChar ~
5040 000E 13\SpecialChar ~
5071 000F F5*02\SpecialChar ~
5101 Variations of this case however will
5106 It is a standard C expression, so I heartily recommend this be the only
5107 way to get the highest order bit, (it is portable).
5108 Of course it will be recognized even if it is embedded in other expressions,
5115 xyz = gint + ((gint >> 15) & 1);
5121 will still be recognized.
5122 \layout Subsubsection
5127 The compiler uses a rule based, pattern matching and re-writing mechanism
5128 for peep-hole optimization.
5133 a peep-hole optimizer by Christopher W.
5134 Fraser (cwfraser@microsoft.com).
5135 A default set of rules are compiled into the compiler, additional rules
5136 may be added with the
5138 --peep-file <filename>
5141 The rule language is best illustrated with examples.
5169 The above rule will change the following assembly sequence:
5199 Note: All occurrences of a
5203 (pattern variable) must denote the same string.
5204 With the above rule, the assembly sequence:
5222 will remain unmodified.
5226 Other special case optimizations may be added by the user (via
5232 some variants of the 8051 MCU allow only
5241 The following two rules will change all
5263 replace { lcall %1 } by { acall %1 }
5265 replace { ljmp %1 } by { ajmp %1 }
5273 inline-assembler code
5275 is also passed through the peep hole optimizer, thus the peephole optimizer
5276 can also be used as an assembly level macro expander.
5277 The rules themselves are MCU dependent whereas the rule language infra-structur
5278 e is MCU independent.
5279 Peephole optimization rules for other MCU can be easily programmed using
5284 The syntax for a rule is as follows:
5290 rule := replace [ restart ] '{' <assembly sequence> '
5328 <assembly sequence> '
5346 '}' [if <functionName> ] '
5354 <assembly sequence> := assembly instruction (each instruction including
5355 labels must be on a separate line).
5359 The optimizer will apply to the rules one by one from the top in the sequence
5360 of their appearance, it will terminate when all rules are exhausted.
5361 If the 'restart' option is specified, then the optimizer will start matching
5362 the rules again from the top, this option for a rule is expensive (performance)
5363 , it is intended to be used in situations where a transformation will trigger
5364 the same rule again.
5365 An example of this (not a good one, it has side effects) is the following
5392 Note that the replace pattern cannot be a blank, but can be a comment line.
5393 Without the 'restart' option only the inner most 'pop' 'push' pair would
5394 be eliminated, i.e.:
5446 the restart option the rule will be applied again to the resulting code
5447 and then all the pop-push pairs will be eliminated to yield:
5465 A conditional function can be attached to a rule.
5466 Attaching rules are somewhat more involved, let me illustrate this with
5497 The optimizer does a look-up of a function name table defined in function
5502 in the source file SDCCpeeph.c, with the name
5507 If it finds a corresponding entry the function is called.
5508 Note there can be no parameters specified for these functions, in this
5513 is crucial, since the function
5517 expects to find the label in that particular variable (the hash table containin
5518 g the variable bindings is passed as a parameter).
5519 If you want to code more such functions, take a close look at the function
5520 labelInRange and the calling mechanism in source file SDCCpeeph.c.
5521 I know this whole thing is a little kludgey, but maybe some day we will
5522 have some better means.
5523 If you are looking at this file, you will also see the default rules that
5524 are compiled into the compiler, you can add your own rules in the default
5525 set there if you get tired of specifying the --peep-file option.
5531 SDCC supports the following #pragma directives.
5532 This directives are applicable only at a function level.
5535 SAVE - this will save all the current options.
5538 RESTORE - will restore the saved options from the last save.
5539 Note that SAVES & RESTOREs cannot be nested.
5540 SDCC uses the same buffer to save the options each time a SAVE is called.
5543 NOGCSE - will stop global subexpression elimination.
5546 NOINDUCTION - will stop loop induction optimizations.
5549 NOJTBOUND - will not generate code for boundary value checking, when switch
5550 statements are turned into jump-tables.
5553 NOOVERLAY - the compiler will not overlay the parameters and local variables
5557 NOLOOPREVERSE - Will not do loop reversal optimization
5560 EXCLUDE NONE | {acc[,b[,dpl[,dph]]] - The exclude pragma disables generation
5561 of pair of push/pop instruction in ISR function (using interrupt keyword).
5562 The directive should be placed immediately before the ISR function definition
5563 and it affects ALL ISR functions following it.
5564 To enable the normal register saving for ISR functions use #pragma\SpecialChar ~
5565 EXCLUDE\SpecialChar ~
5569 CALLEE-SAVES function1[,function2[,function3...]] - The compiler by default
5570 uses a caller saves convention for register saving across function calls,
5571 however this can cause unneccessary register pushing & popping when calling
5572 small functions from larger functions.
5573 This option can be used to switch the register saving convention for the
5574 function names specified.
5575 The compiler will not save registers when calling these functions, extra
5576 code will be generated at the entry & exit for these functions to save
5577 & restore the registers used by these functions, this can SUBSTANTIALLY
5578 reduce code & improve run time performance of the generated code.
5579 In future the compiler (with interprocedural analysis) will be able to
5580 determine the appropriate scheme to use for each function call.
5581 If --callee-saves command line option is used, the function names specified
5582 in #pragma\SpecialChar ~
5583 CALLEE-SAVES is appended to the list of functions specified inthe
5587 The pragma's are intended to be used to turn-off certain optimizations which
5588 might cause the compiler to generate extra stack / data space to store
5589 compiler generated temporary variables.
5590 This usually happens in large functions.
5591 Pragma directives should be used as shown in the following example, they
5592 are used to control options & optimizations for a given function; pragmas
5593 should be placed before and/or after a function, placing pragma's inside
5594 a function body could have unpredictable results.
5600 #pragma SAVE /* save the current settings */
5602 #pragma NOGCSE /* turnoff global subexpression elimination */
5604 #pragma NOINDUCTION /* turn off induction optimizations */
5626 #pragma RESTORE /* turn the optimizations back on */
5632 The compiler will generate a warning message when extra space is allocated.
5633 It is strongly recommended that the SAVE and RESTORE pragma's be used when
5634 changing options for a function.
5639 <pending: this is messy and incomplete>
5644 Compiler support routines (_gptrget, _mulint etc)
5647 Stdclib functions (puts, printf, strcat etc)
5650 Math functions (sin, pow, sqrt etc)
5653 Interfacing with Assembly Routines
5654 \layout Subsubsection
5656 Global Registers used for Parameter Passing
5659 The compiler always uses the global registers
5667 to pass the first parameter to a routine.
5668 The second parameter onwards is either allocated on the stack (for reentrant
5669 routines or if --stack-auto is used) or in the internal / external ram
5670 (depending on the memory model).
5672 \layout Subsubsection
5674 Assembler Routine(non-reentrant)
5677 In the following example the function cfunc calls an assembler routine asm_func,
5678 which takes two parameters.
5684 extern int asm_func(unsigned char, unsigned char);
5688 int c_func (unsigned char i, unsigned char j)
5696 return asm_func(i,j);
5710 return c_func(10,9);
5718 The corresponding assembler function is:
5724 .globl _asm_func_PARM_2
5788 add a,_asm_func_PARM_2
5824 Note here that the return values are placed in 'dpl' - One byte return value,
5825 'dpl' LSB & 'dph' MSB for two byte values.
5826 'dpl', 'dph' and 'b' for three byte values (generic pointers) and 'dpl','dph','
5827 b' & 'acc' for four byte values.
5830 The parameter naming convention is _<function_name>_PARM_<n>, where n is
5831 the parameter number starting from 1, and counting from the left.
5832 The first parameter is passed in
5833 \begin_inset Quotes eld
5837 \begin_inset Quotes erd
5840 for One bye parameter,
5841 \begin_inset Quotes eld
5845 \begin_inset Quotes erd
5849 \begin_inset Quotes eld
5853 \begin_inset Quotes erd
5857 \begin_inset Quotes eld
5861 \begin_inset Quotes erd
5864 for four bytes, the varible name for the second parameter will be _<function_na
5869 Assemble the assembler routine with the following command:
5876 asx8051 -losg asmfunc.asm
5883 Then compile and link the assembler routine to the C source file with the
5891 sdcc cfunc.c asmfunc.rel
5892 \layout Subsubsection
5894 Assembler Routine(reentrant)
5897 In this case the second parameter onwards will be passed on the stack, the
5898 parameters are pushed from right to left i.e.
5899 after the call the left most parameter will be on the top of the stack.
5906 extern int asm_func(unsigned char, unsigned char);
5910 int c_func (unsigned char i, unsigned char j) reentrant
5918 return asm_func(i,j);
5932 return c_func(10,9);
5940 The corresponding assembler routine is:
6050 The compiling and linking procedure remains the same, however note the extra
6051 entry & exit linkage required for the assembler code, _bp is the stack
6052 frame pointer and is used to compute the offset into the stack for parameters
6053 and local variables.
6059 The external stack is located at the start of the external ram segment,
6060 and is 256 bytes in size.
6061 When --xstack option is used to compile the program, the parameters and
6062 local variables of all reentrant functions are allocated in this area.
6063 This option is provided for programs with large stack space requirements.
6064 When used with the --stack-auto option, all parameters and local variables
6065 are allocated on the external stack (note support libraries will need to
6066 be recompiled with the same options).
6069 The compiler outputs the higher order address byte of the external ram segment
6070 into PORT P2, therefore when using the External Stack option, this port
6071 MAY NOT be used by the application program.
6077 Deviations from the compliancy.
6080 functions are not always reentrant.
6083 structures cannot be assigned values directly, cannot be passed as function
6084 parameters or assigned to each other and cannot be a return value from
6111 s1 = s2 ; /* is invalid in SDCC although allowed in ANSI */
6122 struct s foo1 (struct s parms) /* is invalid in SDCC although allowed in
6144 return rets;/* is invalid in SDCC although allowed in ANSI */
6149 'long long' (64 bit integers) not supported.
6152 'double' precision floating point not supported.
6155 No support for setjmp and longjmp (for now).
6158 Old K&R style function declarations are NOT allowed.
6164 foo(i,j) /* this old style of function declarations */
6166 int i,j; /* are valid in ANSI but not valid in SDCC */
6180 functions declared as pointers must be dereferenced during the call.
6191 /* has to be called like this */
6193 (*foo)(); /* ansi standard allows calls to be made like 'foo()' */
6196 Cyclomatic Complexity
6199 Cyclomatic complexity of a function is defined as the number of independent
6200 paths the program can take during execution of the function.
6201 This is an important number since it defines the number test cases you
6202 have to generate to validate the function.
6203 The accepted industry standard for complexity number is 10, if the cyclomatic
6204 complexity reported by SDCC exceeds 10 you should think about simplification
6205 of the function logic.
6206 Note that the complexity level is not related to the number of lines of
6208 Large functions can have low complexity, and small functions can have large
6214 SDCC uses the following formula to compute the complexity:
6219 complexity = (number of edges in control flow graph) - (number of nodes
6220 in control flow graph) + 2;
6224 Having said that the industry standard is 10, you should be aware that in
6225 some cases it be may unavoidable to have a complexity level of less than
6227 For example if you have switch statement with more than 10 case labels,
6228 each case label adds one to the complexity level.
6229 The complexity level is by no means an absolute measure of the algorithmic
6230 complexity of the function, it does however provide a good starting point
6231 for which functions you might look at for further optimization.
6237 Here are a few guidelines that will help the compiler generate more efficient
6238 code, some of the tips are specific to this compiler others are generally
6239 good programming practice.
6242 Use the smallest data type to represent your data-value.
6243 If it is known in advance that the value is going to be less than 256 then
6244 use a 'char' instead of a 'short' or 'int'.
6247 Use unsigned when it is known in advance that the value is not going to
6249 This helps especially if you are doing division or multiplication.
6252 NEVER jump into a LOOP.
6255 Declare the variables to be local whenever possible, especially loop control
6256 variables (induction).
6259 Since the compiler does not do implicit integral promotion, the programmer
6260 should do an explicit cast when integral promotion is required.
6263 Reducing the size of division, multiplication & modulus operations can reduce
6264 code size substantially.
6265 Take the following code for example.
6271 foobar(unsigned int p1, unsigned char ch)
6275 unsigned char ch1 = p1 % ch ;
6286 For the modulus operation the variable ch will be promoted to unsigned int
6287 first then the modulus operation will be performed (this will lead to a
6288 call to support routine _moduint()), and the result will be casted to a
6290 If the code is changed to
6296 foobar(unsigned int p1, unsigned char ch)
6300 unsigned char ch1 = (unsigned char)p1 % ch ;
6311 It would substantially reduce the code generated (future versions of the
6312 compiler will be smart enough to detect such optimization oppurtunities).
6315 Notes on MCS51 memory layout
6318 The 8051 family of micro controller have a minimum of 128 bytes of internal
6319 memory which is structured as follows
6323 - Bytes 00-1F - 32 bytes to hold up to 4 banks of the registers R7 to R7
6326 - Bytes 20-2F - 16 bytes to hold 128 bit variables and
6328 - Bytes 30-7F - 60 bytes for general purpose use.
6332 Normally the SDCC compiler will only utilise the first bank of registers,
6333 but it is possible to specify that other banks of registers should be used
6334 in interrupt routines.
6335 By default, the compiler will place the stack after the last bank of used
6337 if the first 2 banks of registers are used, it will position the base of
6338 the internal stack at address 16 (0X10).
6339 This implies that as the stack grows, it will use up the remaining register
6340 banks, and the 16 bytes used by the 128 bit variables, and 60 bytes for
6341 general purpose use.
6344 By default, the compiler uses the 60 general purpose bytes to hold "near
6346 The compiler/optimiser may also declare some Local Variables in this area
6351 If any of the 128 bit variables are used, or near data is being used then
6352 care needs to be taken to ensure that the stack does not grow so much that
6353 it starts to over write either your bit variables or "near data".
6354 There is no runtime checking to prevent this from happening.
6357 The amount of stack being used is affected by the use of the "internal stack"
6358 to save registers before a subroutine call is made (--stack-auto will declare
6359 parameters and local variables on the stack) and the number of nested subroutin
6363 If you detect that the stack is over writing you data, then the following
6365 --xstack will cause an external stack to be used for saving registers and
6366 (if --stack-auto is being used) storing parameters and local variables.
6367 However this will produce more code which will be slower to execute.
6371 --stack-loc will allow you specify the start of the stack, i.e.
6372 you could start it after any data in the general purpose area.
6373 However this may waste the memory not used by the register banks and if
6374 the size of the "near data" increases, it may creep into the bottom of
6378 --stack-after-data, similar to the --stack-loc, but it automatically places
6379 the stack after the end of the "near data".
6380 Again this could waste any spare register space.
6383 --data-loc allows you to specify the start address of the near data.
6384 This could be used to move the "near data" further away from the stack
6385 giving it more room to grow.
6386 This will only work if no bit variables are being used and the stack can
6387 grow to use the bit variable space.
6395 If you find that the stack is over writing your bit variables or "near data"
6396 then the approach which best utilised the internal memory is to position
6397 the "near data" after the last bank of used registers or, if you use bit
6398 variables, after the last bit variable by using the --data-loc, e.g.
6399 if two register banks are being used and no bit variables, --data-loc 16,
6400 and use the --stack-after-data option.
6403 If bit variables are being used, another method would be to try and squeeze
6404 the data area in the unused register banks if it will fit, and start the
6405 stack after the last bit variable.
6408 Retargetting for other MCUs.
6411 The issues for retargetting the compiler are far too numerous to be covered
6413 What follows is a brief description of each of the seven phases of the
6414 compiler and its MCU dependency.
6417 Parsing the source and building the annotated parse tree.
6418 This phase is largely MCU independent (except for the language extensions).
6419 Syntax & semantic checks are also done in this phase, along with some initial
6420 optimizations like back patching labels and the pattern matching optimizations
6421 like bit-rotation etc.
6424 The second phase involves generating an intermediate code which can be easy
6425 manipulated during the later phases.
6426 This phase is entirely MCU independent.
6427 The intermediate code generation assumes the target machine has unlimited
6428 number of registers, and designates them with the name iTemp.
6429 The compiler can be made to dump a human readable form of the code generated
6430 by using the --dumpraw option.
6433 This phase does the bulk of the standard optimizations and is also MCU independe
6435 This phase can be broken down into several sub-phases:
6439 Break down intermediate code (iCode) into basic blocks.
6441 Do control flow & data flow analysis on the basic blocks.
6443 Do local common subexpression elimination, then global subexpression elimination
6445 Dead code elimination
6449 If loop optimizations caused any changes then do 'global subexpression eliminati
6450 on' and 'dead code elimination' again.
6453 This phase determines the live-ranges; by live range I mean those iTemp
6454 variables defined by the compiler that still survive after all the optimization
6456 Live range analysis is essential for register allocation, since these computati
6457 on determines which of these iTemps will be assigned to registers, and for
6461 Phase five is register allocation.
6462 There are two parts to this process.
6466 The first part I call 'register packing' (for lack of a better term).
6467 In this case several MCU specific expression folding is done to reduce
6472 The second part is more MCU independent and deals with allocating registers
6473 to the remaining live ranges.
6474 A lot of MCU specific code does creep into this phase because of the limited
6475 number of index registers available in the 8051.
6478 The Code generation phase is (unhappily), entirely MCU dependent and very
6479 little (if any at all) of this code can be reused for other MCU.
6480 However the scheme for allocating a homogenized assembler operand for each
6481 iCode operand may be reused.
6484 As mentioned in the optimization section the peep-hole optimizer is rule
6485 based system, which can reprogrammed for other MCUs.
6488 SDCDB - Source Level Debugger
6491 SDCC is distributed with a source level debugger.
6492 The debugger uses a command line interface, the command repertoire of the
6493 debugger has been kept as close to gdb (the GNU debugger) as possible.
6494 The configuration and build process is part of the standard compiler installati
6495 on, which also builds and installs the debugger in the target directory
6496 specified during configuration.
6497 The debugger allows you debug BOTH at the C source and at the ASM source
6501 Compiling for Debugging
6506 debug option must be specified for all files for which debug information
6508 The complier generates a .cdb file for each of these files.
6509 The linker updates the .cdb file with the address information.
6510 This .cdb is used by the debugger.
6513 How the Debugger Works
6516 When the --debug option is specified the compiler generates extra symbol
6517 information some of which are put into the the assembler source and some
6518 are put into the .cdb file, the linker updates the .cdb file with the address
6519 information for the symbols.
6520 The debugger reads the symbolic information generated by the compiler &
6521 the address information generated by the linker.
6522 It uses the SIMULATOR (Daniel's S51) to execute the program, the program
6523 execution is controlled by the debugger.
6524 When a command is issued for the debugger, it translates it into appropriate
6525 commands for the simulator.
6528 Starting the Debugger
6531 The debugger can be started using the following command line.
6532 (Assume the file you are debugging has the file name foo).
6546 The debugger will look for the following files.
6549 foo.c - the source file.
6552 foo.cdb - the debugger symbol information file.
6555 foo.ihx - the intel hex format object file.
6558 Command Line Options.
6561 --directory=<source file directory> this option can used to specify the
6562 directory search list.
6563 The debugger will look into the directory list specified for source, cdb
6565 The items in the directory list must be separated by ':', e.g.
6566 if the source files can be in the directories /home/src1 and /home/src2,
6567 the --directory option should be --directory=/home/src1:/home/src2.
6568 Note there can be no spaces in the option.
6572 -cd <directory> - change to the <directory>.
6575 -fullname - used by GUI front ends.
6578 -cpu <cpu-type> - this argument is passed to the simulator please see the
6579 simulator docs for details.
6582 -X <Clock frequency > this options is passed to the simulator please see
6583 the simulator docs for details.
6586 -s <serial port file> passed to simulator see the simulator docs for details.
6589 -S <serial in,out> passed to simulator see the simulator docs for details.
6595 As mention earlier the command interface for the debugger has been deliberately
6596 kept as close the GNU debugger gdb, as possible.
6597 This will help the integration with existing graphical user interfaces
6598 (like ddd, xxgdb or xemacs) existing for the GNU debugger.
6599 \layout Subsubsection
6601 break [line | file:line | function | file:function]
6604 Set breakpoint at specified line or function:
6613 sdcdb>break foo.c:100
6617 sdcdb>break foo.c:funcfoo
6618 \layout Subsubsection
6620 clear [line | file:line | function | file:function ]
6623 Clear breakpoint at specified line or function:
6632 sdcdb>clear foo.c:100
6636 sdcdb>clear foo.c:funcfoo
6637 \layout Subsubsection
6642 Continue program being debugged, after breakpoint.
6643 \layout Subsubsection
6648 Execute till the end of the current function.
6649 \layout Subsubsection
6654 Delete breakpoint number 'n'.
6655 If used without any option clear ALL user defined break points.
6656 \layout Subsubsection
6658 info [break | stack | frame | registers ]
6661 info break - list all breakpoints
6664 info stack - show the function call stack.
6667 info frame - show information about the current execution frame.
6670 info registers - show content of all registers.
6671 \layout Subsubsection
6676 Step program until it reaches a different source line.
6677 \layout Subsubsection
6682 Step program, proceeding through subroutine calls.
6683 \layout Subsubsection
6688 Start debugged program.
6689 \layout Subsubsection
6694 Print type information of the variable.
6695 \layout Subsubsection
6700 print value of variable.
6701 \layout Subsubsection
6706 load the given file name.
6707 Note this is an alternate method of loading file for debugging.
6708 \layout Subsubsection
6713 print information about current frame.
6714 \layout Subsubsection
6719 Toggle between C source & assembly source.
6720 \layout Subsubsection
6725 Send the string following '!' to the simulator, the simulator response is
6727 Note the debugger does not interpret the command being sent to the simulator,
6728 so if a command like 'go' is sent the debugger can loose its execution
6729 context and may display incorrect values.
6730 \layout Subsubsection
6737 My name is Bobby Brown"
6740 Interfacing with XEmacs.
6743 Two files (in emacs lisp) are provided for the interfacing with XEmacs,
6744 sdcdb.el and sdcdbsrc.el.
6745 These two files can be found in the $(prefix)/bin directory after the installat
6747 These files need to be loaded into XEmacs for the interface to work.
6748 This can be done at XEmacs startup time by inserting the following into
6749 your '.xemacs' file (which can be found in your HOME directory):
6755 (load-file sdcdbsrc.el)
6761 .xemacs is a lisp file so the () around the command is REQUIRED.
6762 The files can also be loaded dynamically while XEmacs is running, set the
6763 environment variable 'EMACSLOADPATH' to the installation bin directory
6764 (<installdir>/bin), then enter the following command ESC-x load-file sdcdbsrc.
6765 To start the interface enter the following command:
6779 You will prompted to enter the file name to be debugged.
6784 The command line options that are passed to the simulator directly are bound
6785 to default values in the file sdcdbsrc.el.
6786 The variables are listed below, these values maybe changed as required.
6789 sdcdbsrc-cpu-type '51
6792 sdcdbsrc-frequency '11059200
6798 The following is a list of key mapping for the debugger interface.
6806 ;; Current Listing ::
6823 binding\SpecialChar ~
6862 -------\SpecialChar ~
6902 sdcdb-next-from-src\SpecialChar ~
6928 sdcdb-back-from-src\SpecialChar ~
6954 sdcdb-cont-from-src\SpecialChar ~
6964 SDCDB continue command
6980 sdcdb-step-from-src\SpecialChar ~
7006 sdcdb-whatis-c-sexp\SpecialChar ~
7016 SDCDB ptypecommand for data at
7080 sdcdbsrc-delete\SpecialChar ~
7094 SDCDB Delete all breakpoints if no arg
7142 given or delete arg (C-u arg x)
7158 sdcdbsrc-frame\SpecialChar ~
7173 SDCDB Display current frame if no arg,
7222 given or display frame arg
7287 sdcdbsrc-goto-sdcdb\SpecialChar ~
7297 Goto the SDCDB output buffer
7313 sdcdb-print-c-sexp\SpecialChar ~
7324 SDCDB print command for data at
7388 sdcdbsrc-goto-sdcdb\SpecialChar ~
7398 Goto the SDCDB output buffer
7414 sdcdbsrc-mode\SpecialChar ~
7430 Toggles Sdcdbsrc mode (turns it off)
7434 ;; C-c C-f\SpecialChar ~
7442 sdcdb-finish-from-src\SpecialChar ~
7450 SDCDB finish command
7454 ;; C-x SPC\SpecialChar ~
7462 sdcdb-break\SpecialChar ~
7480 Set break for line with point
7482 ;; ESC t\SpecialChar ~
7492 sdcdbsrc-mode\SpecialChar ~
7508 Toggle Sdcdbsrc mode
7510 ;; ESC m\SpecialChar ~
7520 sdcdbsrc-srcmode\SpecialChar ~
7544 The Z80 and gbz80 port
7547 SDCC can target both the Zilog Z80 and the Nintendo Gameboy's Z80-like gbz80.
7548 The port is incomplete - long support is incomplete (mul, div and mod are
7549 unimplimented), and both float and bitfield support is missing.
7550 Apart from that the code generated is correct.
7553 As always, the code is the authoritave reference - see z80/ralloc.c and z80/gen.c.
7554 The stack frame is similar to that generated by the IAR Z80 compiler.
7555 IX is used as the base pointer, HL is used as a temporary register, and
7556 BC and DE are available for holding varibles.
7557 IY is currently unusued.
7558 Return values are stored in HL.
7559 One bad side effect of using IX as the base pointer is that a functions
7560 stack frame is limited to 127 bytes - this will be fixed in a later version.
7566 SDCC has grown to be a large project.
7567 The compiler alone (without the preprocessor, assembler and linker) is
7568 about 40,000 lines of code (blank stripped).
7569 The open source nature of this project is a key to its continued growth
7571 You gain the benefit and support of many active software developers and
7573 Is SDCC perfect? No, that's why we need your help.
7574 The developers take pride in fixing reported bugs.
7575 You can help by reporting the bugs and helping other SDCC users.
7576 There are lots of ways to contribute, and we encourage you to take part
7577 in making SDCC a great software package.
7583 Send an email to the mailing list at 'user-sdcc@sdcc.sourceforge.net' or 'devel-sd
7584 cc@sdcc.sourceforge.net'.
7585 Bugs will be fixed ASAP.
7586 When reporting a bug, it is very useful to include a small test program
7587 which reproduces the problem.
7588 If you can isolate the problem by looking at the generated assembly code,
7589 this can be very helpful.
7590 Compiling your program with the --dumpall option can sometimes be useful
7591 in locating optimization problems.
7597 Sandeep Dutta (sandeep.dutta@usa.net) - SDCC, the compiler, MCS51 code generator,
7600 Alan Baldwin (baldwin@shop-pdp.kent.edu) - Initial version of ASXXXX & ASLINK.
7603 John Hartman (jhartman@compuserve.com) - Porting ASXXX & ASLINK for 8051
7606 Obukhov (dso@usa.net) - malloc & serial i/o routines.
7609 Daniel Drotos (drdani@mazsola.iit.uni-miskolc.hu) - for his Freeware simulator
7611 Malini Dutta(malini_dutta@hotmail.com) - my wife for her patience and support.
7613 Unknown - for the GNU C - preprocessor.
7615 Michael Hope - The Z80 and Z80GB port, 186 development
7617 Kevin Vigor - The DS390 port.
7619 Johan Knol - Lots of fixes and enhancements, DS390/TINI libs.
7621 Scott Datallo - The PIC port.
7627 Thanks to all the other volunteer developers who have helped with coding,
7628 testing, web-page creation, distribution sets, etc.
7629 You know who you are :-)
7636 This document was initially written by Sandeep Dutta
7639 All product names mentioned herein may be trademarks of their respective
7645 \begin_inset LatexCommand \printindex{}
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