"fix" bug 585128

[fw/sdcc] / doc / sdccman.lyx

#LyX 1.1 created this file. For more info see http://www.lyx.org/
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\use_geometry 0
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\paragraph_separation indent
\defskip medskip
\quotes_language swedish
\quotes_times 2
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\layout Title

SDCC Compiler User Guide
\layout Standard


\begin_inset LatexCommand \tableofcontents{}

\end_inset 


\layout Section

Introduction
\layout Subsection

About SDCC
\layout Standard


\series bold 
SDCC
\series default 
 is a Freeware, retargettable, optimizing ANSI-C compiler by 
\series bold 
Sandeep Dutta
\series default 
 designed for 8 bit Microprocessors.
 The current version targets Intel MCS51 based Microprocessors(8051,8052,
 etc), Zilog Z80 based MCUs, and the Dallas DS80C390 variant.
 It can be retargetted for other microprocessors, support for PIC, AVR and
 186 is under development.
 The entire source code for the compiler is distributed under GPL.
 SDCC uses ASXXXX & ASLINK, a Freeware, retargettable assembler & linker.
 SDCC has extensive language extensions suitable for utilizing various microcont
rollers and underlying hardware effectively.
 
\newline 

\newline 
In addition to the MCU specific optimizations SDCC also does a host of standard
 optimizations like:
\layout Itemize

global sub expression elimination, 
\layout Itemize

loop optimizations (loop invariant, strength reduction of induction variables
 and loop reversing), 
\layout Itemize

constant folding & propagation, 
\layout Itemize

copy propagation, 
\layout Itemize

dead code elimination 
\layout Itemize

jumptables for 
\emph on 
switch
\emph default 
 statements.
\layout Standard

For the back-end SDCC uses a global register allocation scheme which should
 be well suited for other 8 bit MCUs.
 
\newline 

\newline 
The peep hole optimizer uses a rule based substitution mechanism which is
 MCU independent.
 
\newline 

\newline 
Supported data-types are:
\layout Itemize

char (8 bits, 1 byte), 
\layout Itemize

short and int (16 bits, 2 bytes), 
\layout Itemize

long (32 bit, 4 bytes)
\layout Itemize

float (4 byte IEEE).
 
\layout Standard

The compiler also allows 
\emph on 
inline assembler code
\emph default 
 to be embedded anywhere in a function.
 In addition, routines developed in assembly can also be called.
\newline 

\newline 
SDCC also provides an option (--cyclomatic) to report the relative complexity
 of a function.
 These functions can then be further optimized, or hand coded in assembly
 if needed.
 
\newline 

\newline 
SDCC also comes with a companion source level debugger SDCDB, the debugger
 currently uses ucSim a freeware simulator for 8051 and other micro-controllers.
 
\newline 

\newline 
The latest version can be downloaded from 
\begin_inset LatexCommand \htmlurl{http://sdcc.sourceforge.net/}

\end_inset 


\series bold 
.
\layout Subsection

Open Source
\layout Standard

All packages used in this compiler system are 
\emph on 
opensource
\emph default 
 and 
\emph on 
freeware
\emph default 
; source code for all the sub-packages (asxxxx assembler/linker, pre-processor)
 is distributed with the package.
 This documentation is maintained using a freeware word processor (LyX).
 
\layout Standard

This program is free software; you can redistribute it and/or modify it
 under the terms of the GNU General Public License as published by the Free
 Software Foundation; either version 2, or (at your option) any later version.
 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE.
 See the GNU General Public License for more details.
 You should have received a copy of the GNU General Public License along
 with this program; if not, write to the Free Software Foundation, 59 Temple
 Place - Suite 330, Boston, MA 02111-1307, USA.
 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve what
 you give them.
 Help stamp out software-hoarding! 
\layout Subsection

Typographic conventions
\layout Standard

Throughout this manual, we will use the following convention.
 Commands you have to type in are printed in 
\family sans 
\series bold 
"sans serif"
\series default 
.

\family default 
 Code samples are printed in 
\family typewriter 
typewriter font.

\family default 
 Interesting items and new terms are printed in 
\emph on 
italicised type.
\layout Subsection

Compatibility with previous versions
\layout Standard

This version has numerous bug fixes compared with the previous version.
 But we also introduced some incompatibilities with older versions.
 Not just for the fun of it, but to make the compiler more stable, efficient
 and ANSI compliant.
 
\newline 

\layout Itemize

short is now equivalent to int (16 bits), it used to be equivalent to char
 (8 bits)
\layout Itemize

the default directory where include, library and documention files are stored
 is no in /usr/local/share
\layout Itemize

char type parameters to vararg functions are casted to int unless explicitly
 casted, e.g.: 
\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
char a=3;
\newline 
\SpecialChar ~
\SpecialChar ~
printf ("%d %c
\backslash 
n", a, (char)a);
\family default 

\newline 
 will push a as an int and as a char resp.
\layout Itemize

option --regextend has been removed
\layout Itemize

option --noreparms has been removed
\layout Standard


\emph on 
<pending: more incompatibilities?>
\layout Subsection

System Requirements
\layout Standard

What do you need before you start installation of SDCC? A computer, and
 a desire to compute.
 The preferred method of installation is to compile SDCC from source using
 GNU gcc and make.
 For Windows some pre-compiled binary distributions are available for your
 convenience.
 You should have some experience with command line tools and compiler use.
\layout Subsection

Other Resources
\layout Standard

The SDCC home page at 
\begin_inset LatexCommand \htmlurl{http://sdcc.sourceforge.net/}

\end_inset 

 is a great place to find distribution sets.
 You can also find links to the user mailing lists that offer help or discuss
 SDCC with other SDCC users.
 Web links to other SDCC related sites can also be found here.
 This document can be found in the DOC directory of the source package as
 a text or HTML file.
 Some of the other tools (simulator and assembler) included with SDCC contain
 their own documentation and can be found in the source distribution.
 If you want the latest unreleased software, the complete source package
 is available directly by anonymous CVS on cvs.sdcc.sourceforge.net.
\layout Subsection

Wishes for the future
\layout Standard

There are (and always will be) some things that could be done.
 Here are some I can think of:
\newline 

\layout Standard


\family sans 
\series bold 
sdcc -c --model-large -o large _atoi.c
\family default 
\series default 
 (where large could be a different basename or a directory)
\newline 

\layout Standard


\family typewriter 
char KernelFunction3(char p) at 0x340;
\newline 

\newline 

\family default 
If you can think of some more, please send them to the list.
\newline 

\newline 

\emph on 
<pending: And then of course a proper index-table
\begin_inset LatexCommand \index{index}

\end_inset 

>
\layout Section

Installation
\layout Subsection

Linux/Unix Installation
\layout Enumerate


\series medium 
Download the source package, it will be named something like sdcc-2.x.x.tgz.
\layout Enumerate


\series medium 
Bring up a command line terminal, such as xterm.
\layout Enumerate


\series medium 
Unpack the file using a command like: 
\family sans 
\series bold 
"tar -xzf sdcc-2.x.x.tgz
\family default 
\series default 
"
\series medium 
, this will create a sub-directory called sdcc with all of the sources.
\layout Enumerate

Change directory into the main SDCC directory, for example type: 
\family sans 
\series bold 
"cd sdcc
\series default 
".
\layout Enumerate


\series medium 
Type 
\family sans 
\series bold 
"./configure
\family default 
\series default 
".
 This configures the package for compilation on your system.
\layout Enumerate


\series medium 
Type 
\family sans 
\series bold 
"make
\family default 
\series default 
"
\series medium 
.

\series default 
 All of the source packages will compile, this can take a while.
\layout Enumerate


\series medium 
Type 
\family sans 
\series bold 
"make install"
\family default 
\series default 
 as root
\series medium 
.

\series default 
 This copies the binary executables, the include files, the libraries and
 the documentation to the install directories.
\layout Subsection

Windows Installation
\layout Standard


\emph on 
<pending: is this complete? where is borland, mingw>
\newline 

\newline 

\emph default 
For installation under Windows you first need to pick between a pre-compiled
 binary package, or installing the source package along with the Cygwin
 package.
 The binary package is the quickest to install, while the Cygwin package
 includes all of the open source power tools used to compile the complete
 SDCC source package in the Windows environment.
 If you are not familiar with the Unix command line environment, you may
 want to read the section on additional information for Windows users prior
 to your initial installation.
\layout Subsubsection

Windows Install Using a Binary Package
\layout Enumerate

Download the binary package and unpack it using your favorite unpacking
 tool (gunzip, WinZip, etc).
 This should unpack to a group of sub-directories.
 An example directory structure after unpacking is: c:
\backslash 
usr
\backslash 
local
\backslash 
bin for the executables, c:
\backslash 
usr
\backslash 
local
\backslash 
share
\backslash 
sdcc
\backslash 
include and c:
\backslash 
usr
\backslash 
local
\backslash 
share
\backslash 
sdcc
\backslash 
lib for the include and libraries.
\layout Enumerate

Adjust your environment PATH to include the location of the bin directory.
 For example, make a setsdcc.bat file with the following: set PATH=c:
\backslash 
usr
\backslash 
local
\backslash 
bin;%PATH%
\layout Enumerate

When you compile with sdcc, you may need to specify the location of the
 lib and include folders.
 For example, sdcc -I c:
\backslash 
usr
\backslash 
local
\backslash 
share
\backslash 
sdcc
\backslash 
include -L c:
\backslash 
usr
\backslash 
local
\backslash 
share
\backslash 
sdcc
\backslash 
lib
\backslash 
small test.c
\layout Subsubsection

Windows Install Using Cygwin
\layout Enumerate


\series medium 
Download and install the cygwin package from the redhat site
\series default 

\begin_inset LatexCommand \htmlurl{http://sources.redhat.com/cygwin/}

\end_inset 


\series medium 
.
 Currently, this involved downloading a small install program which then
 automates downloading and installing 
\series default 
selected parts of
\series medium 
 the package
\series default 
 (a large 80M byte sized dowload for the whole thing)
\series medium 
.

\series default 
 
\layout Enumerate


\series medium 
Bring up a 
\series default 
Unix/Bash 
\series medium 
command line terminal from the Cygwin menu.
\layout Enumerate


\series medium 
Follow the instructions in the preceding Linux/Unix installation section.
\layout Subsection

Testing out the SDCC Compiler
\layout Standard

The first thing you should do after installing your SDCC compiler is to
 see if it runs.
 Type 
\family sans 
\series bold 
"sdcc --version"
\family default 
\series default 
 at the prompt, and the program should run and tell you the version.
 If it doesn't run, or gives a message about not finding sdcc program, then
 you need to check over your installation.
 Make sure that the sdcc bin directory is in your executable search path
 defined by the PATH environment setting (see the Trouble-shooting section
 for suggestions).
 Make sure that the sdcc program is in the bin folder, if not perhaps something
 did not install correctly.
\newline 

\newline 

\series medium 
SDCC binaries are commonly installed in a directory arrangement like this:
\series default 

\newline 

\newline 

\begin_inset  Tabular
<lyxtabular version="2" rows="3" columns="2">
<features rotate="false" islongtable="false" endhead="0" endfirsthead="0" endfoot="0" endlastfoot="0">
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<column alignment="left" valignment="top" leftline="true" rightline="true" width="" special="">
<row topline="true" bottomline="true" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

/
\series medium 
usr/local/bin
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard


\series medium 
Holds executables(sdcc, s51, aslink, 
\series default 
...
\series medium 
)
\end_inset 
</cell>
</row>
<row topline="true" bottomline="false" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

/
\series medium 
usr/local/share/sdcc/lib 
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard


\series medium 
Holds common C 
\series default 
libraries
\end_inset 
</cell>
</row>
<row topline="true" bottomline="true" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

/
\series medium 
usr/local/share/sdcc/include
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard


\series medium 
Holds common C header files
\end_inset 
</cell>
</row>
</lyxtabular>

\end_inset 


\newline 

\newline 

\series medium 
Make sure the compiler works on a very simple example.
 Type in the following test.c program using your favorite editor:
\series default 

\newline 

\emph on 

\newline 

\family typewriter 
\emph default 
int test(int t) {
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return t+3;
\newline 
}
\family default 

\newline 

\emph on 

\newline 

\series medium 
\emph default 
Compile this using the following command: 
\family sans 
\series bold 
"sdcc -c test.c".

\family default 
\series default 
 
\series medium 
If all goes well, the compiler will generate a test.asm and test.rel file.
 Congratulations, you've just compiled your first program with SDCC.
 We used the -c option to tell SDCC not to link the generated code, just
 to keep things simple for this step.
\series default 

\newline 

\newline 

\series medium 
The next step is to try it with the linker.
 Type in 
\family sans 
\series bold 
"sdcc test.c
\family default 
\series default 
"
\series medium 
.
 If all goes well the compiler will link with the libraries and produce
 a test.ihx output file.
 If this step fails
\series default 
 
\series medium 
(no test.ihx, and the linker generates warnings), then the problem is most
 likely that sdcc cannot find the 
\series default 
/
\series medium 
usr/local/share/sdcc/lib directory
\series default 
 
\series medium 
(see the Install trouble-shooting section for suggestions).
\series default 

\newline 

\newline 

\series medium 
The final test is to ensure sdcc can use the 
\series default 
standard
\series medium 
 header files and libraries.
 Edit test.c and change it to the following:
\series default 

\newline 

\newline 
#include <string.h>
\newline 
main() {
\newline 

\family typewriter 
char str1[10];
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
strcpy(str1, "testing");
\newline 
}
\newline 

\newline 

\family default 
\series medium 
Compile this by typing 
\family sans 
\series bold 
"sdcc test.c"
\family default 
\series medium 
.
 This should generate a test.ihx output file, and it should give no warnings
 such as not finding the string.h file.
 If it cannot find the string.h file, then the problem is that sdcc cannot
 find the /usr/local/share/sdcc/include directory
\series default 
 
\series medium 
(see the Install trouble-shooting section for suggestions).
\layout Subsection

Install Trouble-shooting
\layout Subsubsection

SDCC cannot find libraries or header files.
\layout Standard

The default installation assumes the libraries and header files are located
 at 
\begin_inset Quotes eld
\end_inset 

/usr/local/share/sdcc/lib
\begin_inset Quotes erd
\end_inset 

 and 
\begin_inset Quotes eld
\end_inset 

/usr/local/share/sdcc/include
\begin_inset Quotes erd
\end_inset 

.
 An alternative is to specify these locations as compiler options like this:
 
\family sans 
\series bold 
"sdcc\SpecialChar ~
-L\SpecialChar ~
/usr/local/sdcc/lib/small\SpecialChar ~
-I\SpecialChar ~
/usr/local/sdcc/include\SpecialChar ~
test.c"
\family default 
\series default 
.
\layout Subsubsection

SDCC does not compile correctly.
\layout Standard

A thing to try is starting from scratch by unpacking the .tgz source package
 again in an empty directory.
 Confure it again and build like:
\newline 

\newline 

\family sans 
\series bold 
make 2&>1 | tee make.log
\family default 
\series default 

\newline 

\newline 
After this you can review the make.log file to locate the problem.
 Or a relevant part of this be attached to an email that could be helpful
 when requesting help from the mailing list.
\layout Subsubsection

What the 
\begin_inset Quotes sld
\end_inset 

./configure
\begin_inset Quotes srd
\end_inset 

 does
\layout Standard

The 
\begin_inset Quotes sld
\end_inset 

./configure
\begin_inset Quotes srd
\end_inset 

 command is a script that analyzes your system and performs some configuration
 to ensure the source package compiles on your system.
 It will take a few minutes to run, and will compile a few tests to determine
 what compiler features are installed.
\layout Subsubsection

What the 
\begin_inset Quotes sld
\end_inset 

make
\begin_inset Quotes srd
\end_inset 

 does.
\layout Standard

This runs the GNU make tool, which automatically compiles all the source
 packages into the final installed binary executables.
\layout Subsubsection

What the 
\begin_inset Quotes sld
\end_inset 

make install
\begin_inset Quotes erd
\end_inset 

 command does.
\layout Standard

This will install the compiler, other executables and libraries in to the
 appropriate system directories.
 The default is to copy the executables to /usr/local/bin and the libraries
 and header files to /usr/local/share/sdcc/lib and /usr/local/share/sdcc/include.
\layout Subsection

Additional Information for Windows Users
\layout Standard


\emph on 
<pending: is this up to date?>
\newline 

\newline 

\emph default 
The standard method of installing on a Unix system involves compiling the
 source package.
 This is easily done under Unix, but under Windows it can be a more difficult
 process.
 The Cygwin is a large package to download, and the compilation runs considerabl
y slower under Windows due to the overhead of the Cygwin tool set.
 An alternative is to install a pre-compiled Windows binary package.
 There are various trade-offs between each of these methods.
 
\layout Standard

The Cygwin package allows a Windows user to run a Unix command line interface
 (bash shell) and also implements a Unix like file system on top of Windows.
 Included are many of the famous GNU software development tools which can
 augment the SDCC compiler.This is great if you have some experience with
 Unix command line tools and file system conventions, if not you may find
 it easier to start by installing a binary Windows package.
 The binary packages work with the Windows file system conventions.
\layout Subsubsection

Getting started with Cygwin
\layout Standard

SDCC is typically distributed as a tarred/gzipped file (.tgz).
 This is a packed file similar to a .zip file.
 Cygwin includes the tools you will need to unpack the SDCC distribution
 (tar and gzip).
 To unpack it, simply follow the instructions under the Linux/Unix install
 section.
 Before you do this you need to learn how to start a cygwin shell and some
 of the basic commands used to move files, change directory, run commands
 and so on.
 The change directory command is 
\family sans 
\series bold 

\begin_inset Quotes eld
\end_inset 

cd
\begin_inset Quotes erd
\end_inset 


\family default 
\series default 
, the move command is 
\family sans 
\series bold 

\begin_inset Quotes eld
\end_inset 

mv
\begin_inset Quotes erd
\end_inset 


\family default 
\series default 
.
 To print the current working directory, type 
\family sans 
\series bold 

\begin_inset Quotes eld
\end_inset 

pwd
\begin_inset Quotes erd
\end_inset 


\family default 
\series default 
.
 To make a directory, use 
\family sans 
\series bold 

\begin_inset Quotes eld
\end_inset 

mkdir
\begin_inset Quotes erd
\end_inset 


\family default 
\series default 
.
\layout Standard

There are some basic differences between Unix and Windows file systems you
 should understand.
 When you type in directory paths, Unix and the Cygwin bash prompt uses
 forward slashes '/' between directories while Windows traditionally uses
 '
\backslash 
' backward slashes.
 So when you work at the Cygwin bash prompt, you will need to use the forward
 '/' slashes.
 Unix does not have a concept of drive letters, such as 
\begin_inset Quotes eld
\end_inset 

c:
\begin_inset Quotes eld
\end_inset 

, instead all files systems attach and appear as directories.
\layout Subsubsection

Running SDCC as Native Compiled Executables
\layout Standard

If you use the pre-compiled binaries, the install directories for the libraries
 and header files may need to be specified on the sdcc command line like
 this: 
\family sans 
\series bold 
"sdcc -L c:
\backslash 
usr
\backslash 
local
\backslash 
sdcc
\backslash 
lib
\backslash 
small -I c:
\backslash 
usr
\backslash 
local
\backslash 
sdcc
\backslash 
include test.c"
\family default 
\series default 
 if you are running outside of a Unix bash shell.
\layout Standard

If you have successfully installed and compiled SDCC with the Cygwin package,
 it is possible to compile into native .exe files by using the additional
 makefiles included for this purpose.
 For example, with the Borland 32-bit compiler you would run 
\family sans 
\series bold 
"make -f Makefile.bcc"
\family default 
\series default 
.
 A command line version of the Borland 32-bit compiler can be downloaded
 from the Inprise web site.
\layout Subsection

SDCC on Other Platforms
\layout Itemize


\series bold 
FreeBSD and other non-GNU Unixes 
\series default 
- Make sure the GNU make is installed as the default make tool.
\layout Itemize

SDCC has been ported to run under a variety of operating systems and processors.
 If you can run GNU GCC/make then chances are good SDCC can be compiled
 and run on your system.
\layout Subsection

Advanced Install Options
\layout Standard

The 
\begin_inset Quotes eld
\end_inset 

configure
\begin_inset Quotes erd
\end_inset 

 command has several options.
 The most commonly used option is --prefix=<directory name>, where <directory
 name> is the final location for the sdcc executables and libraries, (default
 location is /usr/local).
 The installation process will create the following directory structure
 under the <directory name> specified (if they do not already exist).
 
\newline 

\newline 
bin/ - binary exectables (add to PATH environment variable)
\newline 
bin/share/
\newline 
bin/share/sdcc/include/ - include header files
\newline 
bin/share/sdcc/lib/
\newline 
bin/share/sdcc/lib/small/ - Object & library files for small model library
\newline 
bin/share/sdcc/lib/large/ - Object & library files for large model library
\newline 
bin/share/sdcc/lib/ds390/ - Object & library files forDS80C390 library
\newline 

\newline 
The command 
\family sans 
\series bold 

\begin_inset Quotes sld
\end_inset 

./configure --prefix=/usr/local
\begin_inset Quotes erd
\end_inset 

 
\family default 
\series default 
will configure the compiler to be installed in directory /usr/local.
\layout Subsection

Components of SDCC
\layout Standard

SDCC is not just a compiler, but a collection of tools by various developers.
 These include linkers, assemblers, simulators and other components.
 Here is a summary of some of the components.
 Note that the included simulator and assembler have separate documentation
 which you can find in the source package in their respective directories.
 As SDCC grows to include support for other processors, other packages from
 various developers are included and may have their own sets of documentation.
\newline 

\newline 
You might want to look at the files which are installed in <installdir>.
 At the time of this writing, we find the following programs:
\newline 
 
\newline 
In <installdir>/bin:
\layout Itemize

sdcc - The compiler.
\layout Itemize

sdcpp - The C preprocessor.
\layout Itemize

asx8051 - The assembler for 8051 type processors.
\layout Itemize

as-z80
\series bold 
, 
\series default 
as-gbz80 - The Z80 and GameBoy Z80 assemblers.
\layout Itemize

aslink -The linker for 8051 type processors.
\layout Itemize

link-z80
\series bold 
, 
\series default 
link-gbz80 - The Z80 and GameBoy Z80 linkers.
\layout Itemize

s51 - The ucSim 8051 simulator.
\layout Itemize

sdcdb - The source debugger.
\layout Itemize

packihx - A tool to pack Intel hex files.
\layout Standard

In <installdir>/share/sdcc/include
\layout Itemize

the include files
\layout Standard

In <installdir>/share/sdcc/lib
\layout Itemize

the sources of the runtime library and the subdirs small large and ds390
 with the precompiled relocatables.
\layout Standard

In <installdir>/share/sdcc/doc
\layout Itemize

the documentation
\layout Standard

As development for other processors proceeds, this list will expand to include
 executables to support processors like AVR, PIC, etc.
\layout Subsubsection

sdcc - The Compiler
\layout Standard

This is the actual compiler, it in turn uses the c-preprocessor and invokes
 the assembler and linkage editor.
\layout Subsubsection

sdcpp (C-Preprocessor)
\layout Standard

The preprocessor is a modified version of the GNU preprocessor.
 The C preprocessor is used to pull in #include sources, process #ifdef
 statements, #defines and so on.
\layout Subsubsection

asx8051, as-z80, as-gbz80, aslink, link-z80, link-gbz80 (The Assemblers
 and Linkage Editors)
\layout Standard

This is retargettable assembler & linkage editor, it was developed by Alan
 Baldwin.
 John Hartman created the version for 8051, and I (Sandeep) have made some
 enhancements and bug fixes for it to work properly with the SDCC.
\layout Subsubsection

s51 - Simulator
\layout Standard

S51 is a freeware, opensource simulator developed by Daniel Drotos (
\begin_inset LatexCommand \url{mailto:drdani@mazsola.iit.uni-miskolc.hu}

\end_inset 

).
 The simulator is built as part of the build process.
 For more information visit Daniel's website at: 
\begin_inset LatexCommand \url{http://mazsola.iit.uni-miskolc.hu/~drdani/embedded/s51}

\end_inset 

 .
\layout Subsubsection

sdcdb - Source Level Debugger
\layout Standard

Sdcdb is the companion source level debugger.
 The current version of the debugger uses Daniel's Simulator S51, but can
 be easily changed to use other simulators.
\layout Section

Using SDCC
\layout Subsection

Compiling
\layout Subsubsection

Single Source File Projects
\layout Standard

For single source file 8051 projects the process is very simple.
 Compile your programs with the following command 
\family sans 
\series bold 
"sdcc sourcefile.c".

\family default 
\series default 
 This will compile, assemble and link your source file.
 Output files are as follows
\newline 

\newline 
sourcefile.asm - Assembler source file created by the compiler
\newline 
sourcefile.lst - Assembler listing file created by the Assembler
\newline 
sourcefile.rst - Assembler listing file updated with linkedit information,
 created by linkage editor
\newline 
sourcefile.sym - symbol listing for the sourcefile, created by the assembler
\newline 
sourcefile.rel - Object file created by the assembler, input to Linkage editor
\newline 
sourcefile.map - The memory map for the load module, created by the Linker
\newline 
sourcefile.ihx - The load module in Intel hex format (you can select the
 Motorola S19 format with --out-fmt-s19)
\newline 
sourcefile.cdb - An optional file (with --debug) containing debug information
\newline 

\layout Subsubsection

Projects with Multiple Source Files
\layout Standard

SDCC can compile only ONE file at a time.
 Let us for example assume that you have a project containing the following
 files:
\newline 

\newline 
foo1.c (contains some functions)
\newline 
foo2.c (contains some more functions)
\newline 
foomain.c (contains more functions and the function main)
\newline 

\size footnotesize 

\newline 

\size default 
The first two files will need to be compiled separately with the commands:
\size footnotesize 
 
\size default 

\newline 

\newline 

\family sans 
\series bold 
sdcc\SpecialChar ~
-c\SpecialChar ~
foo1.c
\family default 
\series default 
\size footnotesize 

\newline 

\family sans 
\series bold 
\size default 
sdcc\SpecialChar ~
-c\SpecialChar ~
foo2.c
\family default 
\series default 

\newline 

\newline 
Then compile the source file containing the 
\emph on 
main()
\emph default 
 function and link the files together with the following command: 
\newline 

\newline 

\family sans 
\series bold 
sdcc\SpecialChar ~
foomain.c\SpecialChar ~
foo1.rel\SpecialChar ~
foo2.rel
\family default 
\series default 

\newline 

\newline 
Alternatively, 
\emph on 
foomain.c 
\emph default 
can be separately compiled as well: 
\family sans 
\series bold 

\newline 

\newline 
sdcc\SpecialChar ~
-c\SpecialChar ~
foomain.c
\newline 
sdcc foomain.rel foo1.rel foo2.rel
\newline 

\newline 

\family default 
\series default 
The file containing the 
\emph on 
main()
\emph default 
 function
\emph on 
 
\emph default 
\noun on 
must
\noun default 
 be the 
\noun on 
first
\noun default 
 file specified in the command line, since the linkage editor processes
 file in the order they are presented to it.
\layout Subsubsection

Projects with Additional Libraries
\layout Standard

Some reusable routines may be compiled into a library, see the documentation
 for the assembler and linkage editor (which are in <installdir>/share/sdcc/doc)
 for how to create a 
\emph on 
.lib
\emph default 
 library file.
 Libraries created in this manner can be included in the command line.
 Make sure you include the -L <library-path> option to tell the linker where
 to look for these files if they are not in the current directory.
 Here is an example, assuming you have the source file 
\emph on 
foomain.c
\emph default 
 and a library
\emph on 
 foolib.lib
\emph default 
 in the directory 
\emph on 
mylib
\emph default 
 (if that is not the same as your current project):
\newline 

\newline 

\family sans 
\series bold 
sdcc foomain.c foolib.lib -L mylib
\newline 

\newline 

\family default 
\series default 
Note here that
\emph on 
 mylib
\emph default 
 must be an absolute path name.
\newline 

\newline 
The most efficient way to use libraries is to keep seperate modules in seperate
 source files.
 The lib file now should name all the modules.rel files.
 For an example see the standard library file 
\emph on 
libsdcc.lib
\emph default 
 in the directory <installdir>/share/lib/small.
\layout Subsection

Command Line Options
\layout Subsubsection

Processor Selection Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mmcs51
\series default 
 Generate code for the MCS51 (8051) family of processors.
 This is the default processor target.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mds390
\series default 
 Generate code for the DS80C390 processor.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mz80
\series default 
 Generate code for the Z80 family of processors.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mgbz80
\series default 
 Generate code for the GameBoy Z80 processor.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mavr
\series default 
 Generate code for the Atmel AVR processor(In development, not complete).
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mpic14
\series default 
 Generate code for the PIC 14-bit processors(In development, not complete).
\layout List
\labelwidthstring 00.00.0000


\series bold 
-mtlcs900h
\series default 
 Generate code for the Toshiba TLCS-900H processor(In development, not complete).
\layout Subsubsection

Preprocessor Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
-I<path>
\series default 
 The additional location where the pre processor will look for <..h> or 
\begin_inset Quotes eld
\end_inset 

..h
\begin_inset Quotes erd
\end_inset 

 files.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-D<macro[=value]>
\series default 
 Command line definition of macros.
 Passed to the pre processor.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-M
\series default 
 Tell the preprocessor to output a rule suitable for make describing the
 dependencies of each object file.
 For each source file, the preprocessor outputs one make-rule whose target
 is the object file name for that source file and whose dependencies are
 all the files `#include'd in it.
 This rule may be a single line or may be continued with `
\backslash 
'-newline if it is long.
 The list of rules is printed on standard output instead of the preprocessed
 C program.
 `-M' implies `-E'.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-C
\series default 
 Tell the preprocessor not to discard comments.
 Used with the `-E' option.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-MM
\size large 
\bar under 
 
\series default 
\size default 
\bar default 
Like `-M' but the output mentions only the user header files included with
 `#include 
\begin_inset Quotes eld
\end_inset 

file"'.
 System header files included with `#include <file>' are omitted.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-Aquestion(answer)
\series default 
 Assert the answer answer for question, in case it is tested with a preprocessor
 conditional such as `#if #question(answer)'.
 `-A-' disables the standard assertions that normally describe the target
 machine.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-Aquestion
\series default 
 (answer) Assert the answer answer for question, in case it is tested with
 a preprocessor conditional such as `#if #question(answer)'.
 `-A-' disables the standard assertions that normally describe the target
 machine.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-Umacro
\series default 
 Undefine macro macro.
 `-U' options are evaluated after all `-D' options, but before any `-include'
 and `-imacros' options.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-dM
\series default 
 Tell the preprocessor to output only a list of the macro definitions that
 are in effect at the end of preprocessing.
 Used with the `-E' option.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-dD
\series default 
 Tell the preprocessor to pass all macro definitions into the output, in
 their proper sequence in the rest of the output.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-dN
\size large 
\bar under 
 
\series default 
\size default 
\bar default 
Like `-dD' except that the macro arguments and contents are omitted.
 Only `#define name' is included in the output.
\layout Subsubsection

Linker Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
-L\SpecialChar ~
--lib-path
\bar under 
 
\series default 
\bar default 
<absolute path to additional libraries> This option is passed to the linkage
 editor's additional libraries search path.
 The path name must be absolute.
 Additional library files may be specified in the command line.
 See section Compiling programs for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--xram-loc
\series default 
<Value> The start location of the external ram, default value is 0.
 The value entered can be in Hexadecimal or Decimal format, e.g.: --xram-loc
 0x8000 or --xram-loc 32768.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--code-loc
\series default 
<Value> The start location of the code segment, default value 0.
 Note when this option is used the interrupt vector table is also relocated
 to the given address.
 The value entered can be in Hexadecimal or Decimal format, e.g.: --code-loc
 0x8000 or --code-loc 32768.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--stack-loc
\series default 
<Value> The initial value of the stack pointer.
 The default value of the stack pointer is 0x07 if only register bank 0
 is used, if other register banks are used then the stack pointer is initialized
 to the location above the highest register bank used.
 eg.
 if register banks 1 & 2 are used the stack pointer will default to location
 0x18.
 The value entered can be in Hexadecimal or Decimal format, eg.
 --stack-loc 0x20 or --stack-loc 32.
 If all four register banks are used the stack will be placed after the
 data segment (equivalent to --stack-after-data)
\layout List
\labelwidthstring 00.00.0000


\series bold 
--stack-after-data
\series default 
 This option will cause the stack to be located in the internal ram after
 the data segment.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--data-loc
\series default 
<Value> The start location of the internal ram data segment, the default
 value is 0x30.The value entered can be in Hexadecimal or Decimal format,
 eg.
 --data-loc 0x20 or --data-loc 32.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--idata-loc
\series default 
<Value> The start location of the indirectly addressable internal ram, default
 value is 0x80.
 The value entered can be in Hexadecimal or Decimal format, eg.
 --idata-loc 0x88 or --idata-loc 136.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--out-fmt-ihx
\bar under 
 
\series default 
\bar default 
The linker output (final object code) is in Intel Hex format.
 (This is the default option).
\layout List
\labelwidthstring 00.00.0000


\series bold 
--out-fmt-s19
\bar under 
 
\series default 
\bar default 
The linker output (final object code) is in Motorola S19 format.
\layout Subsubsection

MCS51 Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
--model-large
\series default 
 Generate code for Large model programs see section Memory Models for more
 details.
 If this option is used all source files in the project should be compiled
 with this option.
 In addition the standard library routines are compiled with small model,
 they will need to be recompiled.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--model-small
\series default 
\size large 
\emph on 
 
\size default 
\emph default 
Generate code for Small Model programs see section Memory Models for more
 details.
 This is the default model.
\layout Subsubsection

DS390 Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
--model-flat24
\series default 
\size large 
\emph on 
 
\size default 
\emph default 
Generate 24-bit flat mode code.
 This is the one and only that the ds390 code generator supports right now
 and is default when using 
\emph on 
-mds390
\emph default 
.
 See section Memory Models for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--stack-10bit
\series default 
 Generate code for the 10 bit stack mode of the Dallas DS80C390 part.
 This is the one and only that the ds390 code generator supports right now
 and is default when using 
\emph on 
-mds390
\emph default 
.
 In this mode, the stack is located in the lower 1K of the internal RAM,
 which is mapped to 0x400000.
 Note that the support is incomplete, since it still uses a single byte
 as the stack pointer.
 This means that only the lower 256 bytes of the potential 1K stack space
 will actually be used.
 However, this does allow you to reclaim the precious 256 bytes of low RAM
 for use for the DATA and IDATA segments.
 The compiler will not generate any code to put the processor into 10 bit
 stack mode.
 It is important to ensure that the processor is in this mode before calling
 any re-entrant functions compiled with this option.
 In principle, this should work with the 
\emph on 
--stack-auto
\emph default 
 option, but that has not been tested.
 It is incompatible with the 
\emph on 
--xstack
\emph default 
 option.
 It also only makes sense if the processor is in 24 bit contiguous addressing
 mode (see the 
\emph on 
--model-flat24 option
\emph default 
).
\layout Subsubsection

Optimization Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
--nogcse
\series default 
 Will not do global subexpression elimination, this option may be used when
 the compiler creates undesirably large stack/data spaces to store compiler
 temporaries.
 A warning message will be generated when this happens and the compiler
 will indicate the number of extra bytes it allocated.
 It recommended that this option NOT be used, #pragma\SpecialChar ~
NOGCSE can be used
 to turn off global subexpression elimination for a given function only.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--noinvariant
\series default 
 Will not do loop invariant optimizations, this may be turned off for reasons
 explained for the previous option.
 For more details of loop optimizations performed see section Loop Invariants.It
 recommended that this option NOT be used, #pragma\SpecialChar ~
NOINVARIANT can be used
 to turn off invariant optimizations for a given function only.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--noinduction
\series default 
 Will not do loop induction optimizations, see section strength reduction
 for more details.It is recommended that this option is NOT used, #pragma\SpecialChar ~
NOINDUCT
ION can be used to turn off induction optimizations for a given function
 only.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--nojtbound
\size large 
\bar under 
 
\series default 
\size default 
\bar default 
 Will not generate boundary condition check when switch statements are implement
ed using jump-tables.
 See section Switch Statements for more details.
 It is recommended that this option is NOT used, #pragma\SpecialChar ~
NOJTBOUND can be
 used to turn off boundary checking for jump tables for a given function
 only.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--noloopreverse
\series default 
\size large 
 
\size default 
Will not do loop reversal optimization.
\layout Subsubsection

Other Options
\layout List
\labelwidthstring 00.00.0000


\series bold 
-c\SpecialChar ~
--compile-only
\series default 
 will compile and assemble the source, but will not call the linkage editor.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-E
\series default 
 Run only the C preprocessor.
 Preprocess all the C source files specified and output the results to standard
 output.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--stack-auto
\series default 
\size large 
\emph on 
 
\size default 
\emph default 
All functions in the source file will be compiled as 
\emph on 
reentrant
\emph default 
, i.e.
 the parameters and local variables will be allocated on the stack.
 see section Parameters and Local Variables for more details.
 If this option is used all source files in the project should be compiled
 with this option.
 
\layout List
\labelwidthstring 00.00.0000


\series bold 
--xstack
\series default 
 Uses a pseudo stack in the first 256 bytes in the external ram for allocating
 variables and passing parameters.
 See section on external stack for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--callee-saves function1[,function2][,function3]....

\series default 
 The compiler by default uses a caller saves convention for register saving
 across function calls, however this can cause unneccessary register pushing
 & popping when calling small functions from larger functions.
 This option can be used to switch the register saving convention for the
 function names specified.
 The compiler will not save registers when calling these functions, no extra
 code will be generated at the entry & exit for these functions to save
 & restore the registers used by these functions, this can SUBSTANTIALLY
 reduce code & improve run time performance of the generated code.
 In the future the compiler (with interprocedural analysis) will be able
 to determine the appropriate scheme to use for each function call.
 DO NOT use this option for built-in functions such as _muluint..., if this
 option is used for a library function the appropriate library function
 needs to be recompiled with the same option.
 If the project consists of multiple source files then all the source file
 should be compiled with the same --callee-saves option string.
 Also see #pragma\SpecialChar ~
CALLEE-SAVES.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--debug
\bar under 
 
\series default 
\bar default 
When this option is used the compiler will generate debug information, that
 can be used with the SDCDB.
 The debug information is collected in a file with .cdb extension.
 For more information see documentation for SDCDB.
\layout List
\labelwidthstring 00.00.0000


\series bold 
\emph on 
--regextend
\bar under 
 
\series default 
\bar default 
 This option is obsolete and isn't supported anymore.
\layout List
\labelwidthstring 00.00.0000


\series bold 
\emph on 
--noregparms
\series default 
 This option is obsolete and isn't supported anymore.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--peep-file
\series default 
<filename> This option can be used to use additional rules to be used by
 the peep hole optimizer.
 See section Peep Hole optimizations for details on how to write these rules.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-S
\size large 
\bar under 
 
\series default 
\size default 
\bar default 
Stop after the stage of compilation proper; do not assemble.
 The output is an assembler code file for the input file specified.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-Wa_asmOption[,asmOption]
\series default 
...
 Pass the asmOption to the assembler.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-Wl_linkOption[,linkOption]
\series default 
...
 Pass the linkOption to the linker.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--int-long-reent
\series default 
\size large 
 
\size default 
 Integer (16 bit) and long (32 bit) libraries have been compiled as reentrant.
 Note by default these libraries are compiled as non-reentrant.
 See section Installation for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--cyclomatic
\bar under 
 
\series default 
\bar default 
This option will cause the compiler to generate an information message for
 each function in the source file.
 The message contains some 
\emph on 
important
\emph default 
 information about the function.
 The number of edges and nodes the compiler detected in the control flow
 graph of the function, and most importantly the 
\emph on 
cyclomatic complexity
\emph default 
 see section on Cyclomatic Complexity for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--float-reent
\bar under 
 
\series default 
\bar default 
 Floating point library is compiled as reentrant.See section Installation
 for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--nooverlay
\series default 
  The compiler will not overlay parameters and local variables of any function,
 see section Parameters and local variables for more details.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--main-return
\series default 
 This option can be used when the code generated is called by a monitor
 program.
 The compiler will generate a 'ret' upon return from the 'main' function.
 The default option is to lock up i.e.
 generate a 'ljmp '.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--no-peep
\series default 
  Disable peep-hole optimization.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--peep-asm
\series default 
  Pass the inline assembler code through the peep hole optimizer.
 This can cause unexpected changes to inline assembler code, please go through
 the peephole optimizer rules defined in the source file tree '<target>/peeph.def
' before using this option.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--iram-size
\series default 
<Value> Causes the linker to check if the interal ram usage is within limits
 of the given value.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--nostdincl
\series default 
 This will prevent the compiler from passing on the default include path
 to the preprocessor.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--nostdlib
\series default 
 This will prevent the compiler from passing on the default library path
 to the linker.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--verbose
\series default 
 Shows the various actions the compiler is performing.
\layout List
\labelwidthstring 00.00.0000


\series bold 
-V
\series default 
 Shows the actual commands the compiler is executing.
\layout Subsubsection

Intermediate Dump Options
\layout Standard

The following options are provided for the purpose of retargetting and debugging
 the compiler.
 These provided a means to dump the intermediate code (iCode) generated
 by the compiler in human readable form at various stages of the compilation
 process.
 
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumpraw
\series default 
 This option will cause the compiler to dump the intermediate code into
 a file of named 
\emph on 
<source filename>.dumpraw
\emph default 
 just after the intermediate code has been generated for a function, i.e.
 before any optimizations are done.
 The basic blocks at this stage ordered in the depth first number, so they
 may not be in sequence of execution.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumpgcse
\series default 
 Will create a dump of iCode's, after global subexpression elimination,
 into a file named 
\emph on 
<source filename>.dumpgcse.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumpdeadcode
\series default 
 Will create a dump of iCode's, after deadcode elimination, into a file
 named 
\emph on 
<source filename>.dumpdeadcode.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumploop
\series default 
\size large 
 
\size default 
Will create a dump of iCode's, after loop optimizations, into a file named
 
\emph on 
<source filename>.dumploop.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumprange
\series default 
\size large 
 
\size default 
Will create a dump of iCode's, after live range analysis, into a file named
 
\emph on 
<source filename>.dumprange.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumlrange
\series default 
 Will dump the life ranges for all symbols.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumpregassign
\bar under 
 
\series default 
\bar default 
Will create a dump of iCode's, after register assignment, into a file named
 
\emph on 
<source filename>.dumprassgn.
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumplrange
\series default 
 Will create a dump of the live ranges of iTemp's
\layout List
\labelwidthstring 00.00.0000


\series bold 
--dumpall
\size large 
\bar under 
 
\series default 
\size default 
\bar default 
Will cause all the above mentioned dumps to be created.
\layout Subsection

MCS51/DS390 Storage Class Language Extensions
\layout Standard

In addition to the ANSI storage classes SDCC allows the following MCS51
 specific storage classes.
\layout Subsubsection

xdata
\layout Standard

Variables declared with this storage class will be placed in the extern
 RAM.
 This is the 
\series bold 
default
\series default 
 storage class for Large Memory model, e.g.:
\newline 

\newline 

\family typewriter 
xdata unsigned char xduc;
\layout Subsubsection

data
\layout Standard

This is the 
\series bold 
default
\series default 
 storage class for Small Memory model.
 Variables declared with this storage class will be allocated in the internal
 RAM, e.g.:
\newline 

\newline 

\family typewriter 
data int iramdata;
\layout Subsubsection

idata
\layout Standard

Variables declared with this storage class will be allocated into the indirectly
 addressable portion of the internal ram of a 8051, e.g.:
\newline 

\newline 

\family typewriter 
idata int idi;
\layout Subsubsection

bit
\layout Standard

This is a data-type and a storage class specifier.
 When a variable is declared as a bit, it is allocated into the bit addressable
 memory of 8051, e.g.:
\newline 

\newline 

\family typewriter 
bit iFlag;
\layout Subsubsection

sfr / sbit
\layout Standard

Like the bit keyword, 
\emph on 
sfr / sbit 
\emph default 
signifies both a data-type and storage class, they are used to describe
 the special function registers and special bit variables of a 8051, eg:
\newline 

\newline 

\family typewriter 
sfr at 0x80 P0; /* special function register P0 at location 0x80 */
\newline 
sbit at 0xd7 CY; /* CY (Carry Flag) */
\layout Subsection

Pointers
\layout Standard

SDCC allows (via language extensions) pointers to explicitly point to any
 of the memory spaces of the 8051.
 In addition to the explicit pointers, the compiler also allows a 
\emph on 
_generic
\emph default 
 class of pointers which can be used to point to any of the memory spaces.
\newline 

\newline 
Pointer declaration examples:
\newline 

\size small 

\newline 

\family typewriter 
\size default 
/* pointer physically in xternal ram pointing to object in internal ram
 */ 
\newline 
data unsigned char * xdata p;
\newline 

\newline 
/* pointer physically in code rom pointing to data in xdata space */ 
\newline 
xdata unsigned char * code p;
\newline 

\newline 
/* pointer physically in code space pointing to data in code space */ 
\newline 
code unsigned char * code p;
\newline 

\newline 
/* the folowing is a generic pointer physically located in xdata space */
\newline 
char * xdata p;
\family default 
\size small 

\newline 

\newline 

\size default 
Well you get the idea.
 
\newline 

\newline 

\emph on 
For compatibility with the previous version of the compiler, the following
 syntax for pointer declaration is still supported but will disappear int
 the near future.
 
\newline 

\newline 

\family typewriter 
unsigned char _xdata *ucxdp; /* pointer to data in external ram */ 
\newline 
unsigned char _data \SpecialChar ~
*ucdp ; /* pointer to data in internal ram */ 
\newline 
unsigned char _code \SpecialChar ~
*uccp ; /* pointer to data in R/O code space */
\newline 
unsigned char _idata *uccp; \SpecialChar ~
/* pointer to upper 128 bytes of ram */
\family default 
\size small 
\emph default 

\newline 

\newline 

\size default 
All unqualified pointers are treated as 3-byte (4-byte for the ds390) 
\emph on 
generic
\emph default 
 pointers.
 These type of pointers can also to be explicitly declared.
\newline 

\newline 

\family typewriter 
unsigned char _generic *ucgp;
\family default 
\size small 

\newline 

\newline 

\size default 
The highest order byte of the 
\emph on 
generic
\emph default 
 pointers contains the data space information.
 Assembler support routines are called whenever data is stored or retrieved
 using 
\emph on 
generic
\emph default 
 pointers.
 These are useful for developing reusable library routines.
 Explicitly specifying the pointer type will generate the most efficient
 code.
 Pointers declared using a mixture of OLD and NEW style could have unpredictable
 results.
\layout Subsection

Parameters & Local Variables
\layout Standard

Automatic (local) variables and parameters to functions can either be placed
 on the stack or in data-space.
 The default action of the compiler is to place these variables in the internal
 RAM (for small model) or external RAM (for Large model).
 This in fact makes them 
\emph on 
static
\emph default 
 so by default functions are non-reentrant.
\layout Standard

They can be placed on the stack either by using the
\emph on 
 --stack-auto
\emph default 
 compiler option or by using the 
\emph on 
reentrant
\emph default 
 keyword in the function declaration, e.g.:
\newline 

\size small 

\newline 

\family typewriter 
\size default 
unsigned char foo(char i) reentrant 
\newline 
{ 
\newline 
...
 
\newline 
}
\newline 

\family default 

\newline 
Since stack space on 8051 is limited, the 
\emph on 
reentrant 
\emph default 
keyword or the
\emph on 
 --stack-auto
\emph default 
 option should be used sparingly.
 Note that the reentrant keyword just means that the parameters & local
 variables will be allocated to the stack, it 
\emph on 
does not
\emph default 
 mean that the function is register bank independent.
\newline 

\newline 
Local variables can be assigned storage classes and absolute addresses,
 e.g.: 
\newline 

\newline 

\family typewriter 
unsigned char foo() {
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
xdata unsigned char i;
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
bit bvar;
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
data at 0x31 unsiged char j;
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
}
\newline 

\newline 

\family default 
In the above example the variable 
\emph on 
i
\emph default 
 will be allocated in the external ram, 
\emph on 
bvar
\emph default 
 in bit addressable space and
\emph on 
 j
\emph default 
 in internal ram.
 When compiled with 
\emph on 
--stack-auto
\emph default 
 or when a function is declared as 
\emph on 
reentrant
\emph default 
 this can only be done for static variables.
\layout Standard

Parameters however are not allowed any storage class, (storage classes for
 parameters will be ignored), their allocation is governed by the memory
 model in use, and the reentrancy options.
\layout Subsection

Overlaying
\layout Standard

For non-reentrant functions SDCC will try to reduce internal ram space usage
 by overlaying parameters and local variables of a function (if possible).
 Parameters and local variables of a function will be allocated to an overlayabl
e segment if the function has 
\emph on 
no other function calls and the function is non-reentrant and the memory
 model is small.

\emph default 
 If an explicit storage class is specified for a local variable, it will
 NOT be overlayed.
\layout Standard

Note that the compiler (not the linkage editor) makes the decision for overlayin
g the data items.
 Functions that are called from an interrupt service routine should be preceded
 by a #pragma\SpecialChar ~
NOOVERLAY if they are not reentrant.
\layout Standard

Also note that the compiler does not do any processing of inline assembler
 code, so the compiler might incorrectly assign local variables and parameters
 of a function into the overlay segment if the inline assembler code calls
 other c-functions that might use the overlay.
 In that case the #pragma\SpecialChar ~
NOOVERLAY should be used.
\layout Standard

Parameters and Local variables of functions that contain 16 or 32 bit multiplica
tion or division will NOT be overlayed since these are implemented using
 external functions, e.g.:
\newline 

\newline 

\family typewriter 
#pragma SAVE 
\newline 
#pragma NOOVERLAY 
\newline 
void set_error(unsigned char errcd) 
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
P3 = errcd;
\newline 
} 
\newline 
#pragma RESTORE 
\newline 

\newline 
void some_isr () interrupt 2 using 1 
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
set_error(10);
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
}
\newline 

\newline 

\family default 
In the above example the parameter 
\emph on 
errcd
\emph default 
 for the function 
\emph on 
set_error
\emph default 
 would be assigned to the overlayable segment if the #pragma\SpecialChar ~
NOOVERLAY was
 not present, this could cause unpredictable runtime behavior when called
 from an ISR.
 The #pragma\SpecialChar ~
NOOVERLAY ensures that the parameters and local variables for
 the function are NOT overlayed.
\layout Subsection

Interrupt Service Routines
\layout Standard

SDCC allows interrupt service routines to be coded in C, with some extended
 keywords.
\newline 

\newline 

\family typewriter 
void timer_isr (void) interrupt 2 using 1 
\newline 
{ 
\newline 
..
 
\newline 
}
\newline 

\newline 

\family default 
The number following the 
\emph on 
interrupt
\emph default 
 keyword is the interrupt number this routine will service.
 The compiler will insert a call to this routine in the interrupt vector
 table for the interrupt number specified.
 The 
\emph on 
using
\emph default 
 keyword is used to tell the compiler to use the specified register bank
 (8051 specific) when generating code for this function.
 Note that when some function is called from an interrupt service routine
 it should be preceded by a #pragma\SpecialChar ~
NOOVERLAY if it is not reentrant.
 A special note here, int (16 bit) and long (32 bit) integer division, multiplic
ation & modulus operations are implemented using external support routines
 developed in ANSI-C, if an interrupt service routine needs to do any of
 these operations then the support routines (as mentioned in a following
 section) will have to be recompiled using the
\emph on 
 --stack-auto
\emph default 
 option and the source file will need to be compiled using the 
\emph on 
--int-long-ren
\emph default 
t compiler option.
\layout Standard

If you have multiple source files in your project, interrupt service routines
 can be present in any of them, but a prototype of the isr MUST be present
 or included in the file that contains the function 
\emph on 
main
\emph default 
.
\layout Standard

Interrupt Numbers and the corresponding address & descriptions for the Standard
 8051 are listed below.
 SDCC will automatically adjust the interrupt vector table to the maximum
 interrupt number specified.
\newline 

\layout Standard


\begin_inset  Tabular
<lyxtabular version="2" rows="6" columns="3">
<features rotate="false" islongtable="false" endhead="0" endfirsthead="0" endfoot="0" endlastfoot="0">
<column alignment="center" valignment="top" leftline="true" rightline="false" width="" special="">
<column alignment="center" valignment="top" leftline="true" rightline="false" width="" special="">
<column alignment="center" valignment="top" leftline="true" rightline="true" width="" special="">
<row topline="true" bottomline="true" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Interrupt #
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Description
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Vector Address
\end_inset 
</cell>
</row>
<row topline="true" bottomline="false" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

External 0
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0x0003
\end_inset 
</cell>
</row>
<row topline="true" bottomline="false" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

1
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Timer 0
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0x000B
\end_inset 
</cell>
</row>
<row topline="true" bottomline="false" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

2
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

External 1
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0x0013
\end_inset 
</cell>
</row>
<row topline="true" bottomline="false" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

3
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Timer 1
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0x001B
\end_inset 
</cell>
</row>
<row topline="true" bottomline="true" newpage="false">
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

4
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="false" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

Serial
\end_inset 
</cell>
<cell multicolumn="0" alignment="center" valignment="top" topline="true" bottomline="false" leftline="true" rightline="true" rotate="false" usebox="none" width="" special="">
\begin_inset Text

\layout Standard

0x0023
\end_inset 
</cell>
</row>
</lyxtabular>

\end_inset 


\newline 

\newline 
If the interrupt service routine is defined without 
\emph on 
using
\emph default 
 a register bank or with register bank 0 (using 0), the compiler will save
 the registers used by itself on the stack upon entry and restore them at
 exit, however if such an interrupt service routine calls another function
 then the entire register bank will be saved on the stack.
 This scheme may be advantageous for small interrupt service routines which
 have low register usage.
\layout Standard

If the interrupt service routine is defined to be using a specific register
 bank then only 
\emph on 
a, b & dptr
\emph default 
 are save and restored, if such an interrupt service routine calls another
 function (using another register bank) then the entire register bank of
 the called function will be saved on the stack.
 This scheme is recommended for larger interrupt service routines.
\layout Standard

Calling other functions from an interrupt service routine is not recommended,
 avoid it if possible.
\newline 

\newline 
Also see the _naked modifier.
\layout Subsection

Critical Functions
\layout Standard

A special keyword may be associated with a function declaring it as 
\emph on 
critical
\emph default 
.
 SDCC will generate code to disable all interrupts upon entry to a critical
 function and enable them back before returning.
 Note that nesting critical functions may cause unpredictable results.
\newline 

\size small 

\newline 

\family typewriter 
\size default 
int foo () critical 
\newline 
{ 
\newline 
...
 
\newline 
...
 
\newline 
}
\newline 

\family default 

\newline 
The critical attribute maybe used with other attributes like 
\emph on 
reentrant.
\layout Subsection

Naked Functions
\layout Standard

A special keyword may be associated with a function declaring it as 
\emph on 
_naked.
 
\emph default 
The 
\emph on 
_naked
\emph default 
 function modifier attribute prevents the compiler from generating prologue
 and epilogue code for that function.
 This means that the user is entirely responsible for such things as saving
 any registers that may need to be preserved, selecting the proper register
 bank, generating the 
\emph on 
return
\emph default 
 instruction at the end, etc.
 Practically, this means that the contents of the function must be written
 in inline assembler.
 This is particularly useful for interrupt functions, which can have a large
 (and often unnecessary) prologue/epilogue.
 For example, compare the code generated by these two functions:
\newline 

\newline 

\family typewriter 
data unsigned char counter;
\newline 
void simpleInterrupt(void) interrupt 1
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
counter++;
\newline 
}
\newline 

\newline 
void nakedInterrupt(void) interrupt 2 _naked
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_asm
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
inc\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_counter
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
reti\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
; MUST explicitly include ret in _naked function.
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_endasm;
\newline 
}
\family default 

\newline 

\newline 
For an 8051 target, the generated simpleInterrupt looks like:
\newline 

\newline 

\family typewriter 
_simpleIterrupt:
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
acc
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
b
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
dpl
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
dph
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
psw
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
psw,#0x00
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
inc\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_counter
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
psw
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
dph
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
dpl
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
b
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
acc
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
reti
\family default 

\newline 

\newline 
whereas nakedInterrupt looks like:
\newline 

\newline 

\family typewriter 
_nakedInterrupt:
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
inc\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_counter
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
reti\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
; MUST explicitly include ret(i) in _naked function.
\family default 

\newline 

\newline 
While there is nothing preventing you from writing C code inside a _naked
 function, there are many ways to shoot yourself in the foot doing this,
 and is is recommended that you stick to inline assembler.
\layout Subsection

Functions using private banks
\layout Standard

The 
\emph on 
using
\emph default 
 attribute (which tells the compiler to use a register bank other than the
 default bank zero) should only be applied to 
\emph on 
interrupt
\emph default 
 functions (see note 1 below).
 This will in most circumstances make the generated ISR code more efficient
 since it will not have to save registers on the stack.
\layout Standard

The 
\emph on 
using
\emph default 
 attribute will have no effect on the generated code for a 
\emph on 
non-interrupt
\emph default 
 function (but may occasionally be useful anyway
\begin_float footnote 
\layout Standard

possible exception: if a function is called ONLY from 'interrupt' functions
 using a particular bank, it can be declared with the same 'using' attribute
 as the calling 'interrupt' functions.
 For instance, if you have several ISRs using bank one, and all of them
 call memcpy(), it might make sense to create a specialized version of memcpy()
 'using 1', since this would prevent the ISR from having to save bank zero
 to the stack on entry and switch to bank zero before calling the function
\end_float 
).
\newline 

\emph on 
(pending: I don't think this has been done yet)
\layout Standard

An 
\emph on 
interrupt
\emph default 
 function using a non-zero bank will assume that it can trash that register
 bank, and will not save it.
 Since high-priority interrupts can interrupt low-priority ones on the 8051
 and friends, this means that if a high-priority ISR 
\emph on 
using
\emph default 
 a particular bank occurs while processing a low-priority ISR 
\emph on 
using
\emph default 
 the same bank, terrible and bad things can happen.
 To prevent this, no single register bank should be 
\emph on 
used
\emph default 
 by both a high priority and a low priority ISR.
 This is probably most easily done by having all high priority ISRs use
 one bank and all low priority ISRs use another.
 If you have an ISR which can change priority at runtime, you're on your
 own: I suggest using the default bank zero and taking the small performance
 hit.
\layout Standard

It is most efficient if your ISR calls no other functions.
 If your ISR must call other functions, it is most efficient if those functions
 use the same bank as the ISR (see note 1 below); the next best is if the
 called functions use bank zero.
 It is very inefficient to call a function using a different, non-zero bank
 from an ISR.
 
\layout Subsection

Absolute Addressing
\layout Standard

Data items can be assigned an absolute address with the 
\emph on 
at <address>
\emph default 
 keyword, in addition to a storage class, e.g.:
\newline 

\newline 

\family typewriter 
xdata at 0x8000 unsigned char PORTA_8255 ;
\newline 

\family default 

\newline 
In the above example the PORTA_8255 will be allocated to the location 0x8000
 of the external ram.
 Note that this feature is provided to give the programmer access to 
\emph on 
memory mapped
\emph default 
 devices attached to the controller.
 The compiler does not actually reserve any space for variables declared
 in this way (they are implemented with an equate in the assembler).
 Thus it is left to the programmer to make sure there are no overlaps with
 other variables that are declared without the absolute address.
 The assembler listing file (.lst) and the linker output files (.rst) and
 (.map) are a good places to look for such overlaps.
\newline 

\newline 
Absolute address can be specified for variables in all storage classes,
 e.g.:
\newline 

\newline 

\family typewriter 
bit at 0x02 bvar;
\newline 

\newline 

\family default 
The above example will allocate the variable at offset 0x02 in the bit-addressab
le space.
 There is no real advantage to assigning absolute addresses to variables
 in this manner, unless you want strict control over all the variables allocated.
\layout Subsection

Startup Code
\layout Standard

The compiler inserts a call to the C routine 
\emph on 
_sdcc__external__startup()
\series bold 
\emph default 
 
\series default 
at the start of the CODE area.
 This routine is in the runtime library.
 By default this routine returns 0, if this routine returns a non-zero value,
 the static & global variable initialization will be skipped and the function
 main will be invoked Other wise static & global variables will be initialized
 before the function main is invoked.
 You could add a 
\emph on 
_sdcc__external__startup()
\emph default 
 routine to your program to override the default if you need to setup hardware
 or perform some other critical operation prior to static & global variable
 initialization.
\layout Subsection

Inline Assembler Code
\layout Standard

SDCC allows the use of in-line assembler with a few restriction as regards
 labels.
 All labels defined within inline assembler code 
\emph on 
has to be
\emph default 
 of the form 
\emph on 
nnnnn$
\emph default 
 where nnnn is a number less than 100 (which implies a limit of utmost 100
 inline assembler labels 
\emph on 
per function
\emph default 
\noun on 
)
\noun default 
.
 It is strongly recommended that each assembly instruction (including labels)
 be placed in a separate line (as the example shows).
 When the 
\emph on 
--peep-asm
\emph default 
 command line option is used, the inline assembler code will be passed through
 the peephole optimizer.
 This might cause some unexpected changes in the inline assembler code.
 Please go throught the peephole optimizer rules defined in file 
\emph on 
SDCCpeeph.def
\emph default 
 carefully before using this option.
\newline 

\newline 

\family typewriter 
_asm 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
b,#10 
\newline 
00001$: 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
djnz\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
b,00001$ 
\newline 
_endasm ;
\family default 
\size small 

\newline 

\newline 

\size default 
The inline assembler code can contain any valid code understood by the assembler
, this includes any assembler directives and comment lines.
 The compiler does not do any validation of the code within the 
\family typewriter 
_asm ...
 _endasm;
\family default 
 keyword pair.
 
\newline 

\newline 
Inline assembler code cannot reference any C-Labels, however it can reference
 labels defined by the inline assembler, e.g.:
\newline 

\newline 

\family typewriter 
foo() { 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
/* some c code */ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_asm 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
; some assembler code 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
ljmp $0003 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_endasm; 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
/* some more c code */ 
\newline 
clabel:\SpecialChar ~
\SpecialChar ~
/* inline assembler cannot reference this label */ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_asm
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
$0003: ;label (can be reference by inline assembler only) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_endasm ; 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
/* some more c code */
\newline 
}
\newline 

\newline 

\family default 
In other words inline assembly code can access labels defined in inline
 assembly within the scope of the funtion.
 
\layout Standard

The same goes the other way, ie.
 labels defines in inline assembly CANNOT be accessed by C statements.
\layout Subsection

int(16 bit) and long (32 bit) Support
\layout Standard

For signed & unsigned int (16 bit) and long (32 bit) variables, division,
 multiplication and modulus operations are implemented by support routines.
 These support routines are all developed in ANSI-C to facilitate porting
 to other MCUs, although some model specific assembler optimations are used.
 The following files contain the described routine, all of them can be found
 in <installdir>/share/sdcc/lib.
\newline 

\newline 

\emph on 
<pending: tabularise this>
\emph default 

\newline 

\newline 
_mulsint.c - signed 16 bit multiplication (calls _muluint)
\newline 
_muluint.c - unsigned 16 bit multiplication
\newline 
_divsint.c - signed 16 bit division (calls _divuint)
\newline 
_divuint.c - unsigned 16 bit division
\newline 
_modsint.c - signed 16 bit modulus (call _moduint)
\newline 
_moduint.c - unsigned 16 bit modulus
\newline 
_mulslong.c - signed 32 bit multiplication (calls _mululong)
\newline 
_mululong.c - unsigned32 bit multiplication
\newline 
_divslong.c - signed 32 division (calls _divulong)
\newline 
_divulong.c - unsigned 32 division
\newline 
_modslong.c - signed 32 bit modulus (calls _modulong)
\newline 
_modulong.c - unsigned 32 bit modulus 
\size footnotesize 

\newline 

\newline 

\size default 
Since they are compiled as 
\emph on 
non-reentrant
\emph default 
, interrupt service routines should not do any of the above operations.
 If this is unavoidable then the above routines will need to be compiled
 with the 
\emph on 
--stack-auto
\emph default 
 option, after which the source program will have to be compiled with 
\emph on 
--int-long-rent
\emph default 
 option.
\layout Subsection

Floating Point Support
\layout Standard

SDCC supports IEEE (single precision 4bytes) floating point numbers.The floating
 point support routines are derived from gcc's floatlib.c and consists of
 the following routines:
\newline 

\newline 

\emph on 
<pending: tabularise this>
\emph default 

\newline 

\newline 
_fsadd.c - add floating point numbers
\newline 
_fssub.c - subtract floating point numbers
\newline 
_fsdiv.c - divide floating point numbers
\newline 
_fsmul.c - multiply floating point numbers
\newline 
_fs2uchar.c - convert floating point to unsigned char
\newline 
_fs2char.c - convert floating point to signed char
\newline 
_fs2uint.c - convert floating point to unsigned int
\newline 
_fs2int.c - convert floating point to signed int
\newline 
_fs2ulong.c - convert floating point to unsigned long
\newline 
_fs2long.c - convert floating point to signed long
\newline 
_uchar2fs.c - convert unsigned char to floating point
\newline 
_char2fs.c - convert char to floating point number
\newline 
_uint2fs.c - convert unsigned int to floating point
\newline 
_int2fs.c - convert int to floating point numbers
\newline 
_ulong2fs.c - convert unsigned long to floating point number
\newline 
_long2fs.c - convert long to floating point number
\size footnotesize 

\newline 

\newline 

\size default 
Note if all these routines are used simultaneously the data space might
 overflow.
 For serious floating point usage it is strongly recommended that the large
 model be used.
\layout Subsection

MCS51 Memory Models
\layout Standard

SDCC allows two memory models for MCS51 code, small and large.
 Modules compiled with different memory models should 
\emph on 
never
\emph default 
 be combined together or the results would be unpredictable.
 The library routines supplied with the compiler are compiled as both small
 and large.
 The compiled library modules are contained in seperate directories as small
 and large so that you can link to either set.
 
\layout Standard

When the large model is used all variables declared without a storage class
 will be allocated into the external ram, this includes all parameters and
 local variables (for non-reentrant functions).
 When the small model is used variables without storage class are allocated
 in the internal ram.
\layout Standard

Judicious usage of the processor specific storage classes and the 'reentrant'
 function type will yield much more efficient code, than using the large
 model.
 Several optimizations are disabled when the program is compiled using the
 large model, it is therefore strongly recommdended that the small model
 be used unless absolutely required.
\layout Subsection

DS390 Memory Models
\layout Standard

The only model supported is Flat 24.
 This generates code for the 24 bit contiguous addressing mode of the Dallas
 DS80C390 part.
 In this mode, up to four meg of external RAM or code space can be directly
 addressed.
 See the data sheets at www.dalsemi.com for further information on this part.
\newline 

\newline 
In older versions of the compiler, this option was used with the MCS51 code
 generator (
\emph on 
-mmcs51
\emph default 
).
 Now, however, the '390 has it's own code generator, selected by the 
\emph on 
-mds390
\emph default 
 switch.
 
\newline 

\newline 
Note that the compiler does not generate any code to place the processor
 into 24 bitmode (although 
\emph on 
tinibios
\emph default 
 in the ds390 libraries will do that for you).
 If you don't use 
\emph on 
tinibios
\emph default 
, the boot loader or similar code must ensure that the processor is in 24
 bit contiguous addressing mode before calling the SDCC startup code.
\newline 

\newline 
Like the 
\emph on 
--model-large
\emph default 
 option, variables will by default be placed into the XDATA segment.
 
\newline 

\newline 
Segments may be placed anywhere in the 4 meg address space using the usual
 --*-loc options.
 Note that if any segments are located above 64K, the -r flag must be passed
 to the linker to generate the proper segment relocations, and the Intel
 HEX output format must be used.
 The -r flag can be passed to the linker by using the option 
\emph on 
-Wl-r
\emph default 
 on the sdcc command line.
 However, currently the linker can not handle code segments > 64k.
\layout Subsection

Defines Created by the Compiler
\layout Standard

The compiler creates the following #defines.
\layout Itemize

SDCC - this Symbol is always defined.
\layout Itemize

SDCC_mcs51 or SDCC_ds390 or SDCC_z80, etc - depending on the model used
 (e.g.: -mds390)
\layout Itemize

__mcs51 or __ds390 or __z80, etc - depending on the model used (e.g.
 -mz80)
\layout Itemize

SDCC_STACK_AUTO - this symbol is defined when 
\emph on 
--stack-auto
\emph default 
 option is used.
\layout Itemize

SDCC_MODEL_SMALL - when 
\emph on 
--model-small
\emph default 
 is used.
\layout Itemize

SDCC_MODEL_LARGE - when 
\emph on 
--model-large
\emph default 
 is used.
\layout Itemize

SDCC_USE_XSTACK - when 
\emph on 
--xstack
\emph default 
 option is used.
\layout Itemize

SDCC_STACK_TENBIT - when 
\emph on 
-mds390
\emph default 
 is used
\layout Itemize

SDCC_MODEL_FLAT24 - when 
\emph on 
-mds390
\emph default 
 is used
\layout Section

SDCC Technical Data
\layout Subsection

Optimizations
\layout Standard

SDCC performs a host of standard optimizations in addition to some MCU specific
 optimizations.
 
\layout Subsubsection

Sub-expression Elimination
\layout Standard

The compiler does local and global common subexpression elimination, e.g.:
 
\newline 

\newline 

\family typewriter 
i = x + y + 1; 
\newline 
j = x + y;
\family default 

\newline 

\newline 
will be translated to
\newline 

\newline 

\family typewriter 
iTemp = x + y 
\newline 
i = iTemp + 1 
\newline 
j = iTemp
\newline 

\family default 

\newline 
Some subexpressions are not as obvious as the above example, e.g.:
\newline 

\newline 

\family typewriter 
a->b[i].c = 10; 
\newline 
a->b[i].d = 11;
\family default 

\newline 

\newline 
In this case the address arithmetic a->b[i] will be computed only once;
 the equivalent code in C would be.
\newline 

\newline 

\family typewriter 
iTemp = a->b[i]; 
\newline 
iTemp.c = 10; 
\newline 
iTemp.d = 11;
\family default 

\newline 

\newline 
The compiler will try to keep these temporary variables in registers.
\layout Subsubsection

Dead-Code Elimination
\layout Standard


\family typewriter 
int global; 
\newline 
void f () { 
\newline 
\SpecialChar ~
\SpecialChar ~
int i; 
\newline 
\SpecialChar ~
\SpecialChar ~
i = 1; \SpecialChar ~
/* dead store */ 
\newline 
\SpecialChar ~
\SpecialChar ~
global = 1;\SpecialChar ~
/* dead store */ 
\newline 
\SpecialChar ~
\SpecialChar ~
global = 2; 
\newline 
\SpecialChar ~
\SpecialChar ~
return; 
\newline 
\SpecialChar ~
\SpecialChar ~
global = 3;\SpecialChar ~
/* unreachable */ 
\newline 
}
\family default 

\newline 

\newline 
will be changed to
\newline 

\newline 

\family typewriter 
int global; void f () 
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
global = 2; 
\newline 
\SpecialChar ~
\SpecialChar ~
return; 
\newline 
}
\layout Subsubsection

Copy-Propagation
\layout Standard


\family typewriter 
int f() { 
\newline 
\SpecialChar ~
\SpecialChar ~
int i, j; 
\newline 
\SpecialChar ~
\SpecialChar ~
i = 10; 
\newline 
\SpecialChar ~
\SpecialChar ~
j = i; 
\newline 
\SpecialChar ~
\SpecialChar ~
return j; 
\newline 
}
\family default 

\newline 

\newline 
will be changed to 
\newline 

\newline 

\family typewriter 
int f() { 
\newline 
\SpecialChar ~
 \SpecialChar ~
 int i,j; 
\newline 
\SpecialChar ~
 \SpecialChar ~
 i = 10; 
\newline 
\SpecialChar ~
 \SpecialChar ~
 j = 10; 
\newline 
\SpecialChar ~
 \SpecialChar ~
 return 10; 
\newline 
}
\newline 

\newline 

\family default 
Note: the dead stores created by this copy propagation will be eliminated
 by dead-code elimination.
\layout Subsubsection

Loop Optimizations
\layout Standard

Two types of loop optimizations are done by SDCC loop invariant lifting
 and strength reduction of loop induction variables.
 In addition to the strength reduction the optimizer marks the induction
 variables and the register allocator tries to keep the induction variables
 in registers for the duration of the loop.
 Because of this preference of the register allocator, loop induction optimizati
on causes an increase in register pressure, which may cause unwanted spilling
 of other temporary variables into the stack / data space.
 The compiler will generate a warning message when it is forced to allocate
 extra space either on the stack or data space.
 If this extra space allocation is undesirable then induction optimization
 can be eliminated either for the entire source file (with --noinduction
 option) or for a given function only using #pragma\SpecialChar ~
NOINDUCTION.
\newline 

\newline 
Loop Invariant:
\newline 

\newline 

\family typewriter 
for (i = 0 ; i < 100 ; i ++) 
\newline 
 \SpecialChar ~
 \SpecialChar ~
f += k + l;
\family default 

\newline 

\newline 
changed to
\newline 

\newline 

\family typewriter 
itemp = k + l; 
\newline 
for (i = 0; i < 100; i++) 
\newline 
\SpecialChar ~
\SpecialChar ~
f += itemp;
\family default 

\newline 

\newline 
As mentioned previously some loop invariants are not as apparent, all static
 address computations are also moved out of the loop.
\newline 

\newline 
Strength Reduction, this optimization substitutes an expression by a cheaper
 expression:
\newline 

\newline 

\family typewriter 
for (i=0;i < 100; i++)
\newline 
\SpecialChar ~
\SpecialChar ~
ar[i*5] = i*3;
\family default 

\newline 

\newline 
changed to
\newline 

\newline 

\family typewriter 
itemp1 = 0; 
\newline 
itemp2 = 0; 
\newline 
for (i=0;i< 100;i++) { 
\newline 
 \SpecialChar ~
 \SpecialChar ~
ar[itemp1] = itemp2; 
\newline 
 \SpecialChar ~
 \SpecialChar ~
itemp1 += 5; 
\newline 
 \SpecialChar ~
 \SpecialChar ~
itemp2 += 3; 
\newline 
}
\family default 

\newline 

\newline 
The more expensive multiplication is changed to a less expensive addition.
\layout Subsubsection

Loop Reversing
\layout Standard

This optimization is done to reduce the overhead of checking loop boundaries
 for every iteration.
 Some simple loops can be reversed and implemented using a 
\begin_inset Quotes eld
\end_inset 

decrement and jump if not zero
\begin_inset Quotes erd
\end_inset 

 instruction.
 SDCC checks for the following criterion to determine if a loop is reversible
 (note: more sophisticated compilers use data-dependency analysis to make
 this determination, SDCC uses a more simple minded analysis).
\layout Itemize

The 'for' loop is of the form 
\newline 

\newline 

\family typewriter 
for (<symbol> = <expression> ; <sym> [< | <=] <expression> ; [<sym>++ |
 <sym> += 1])
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
<for body>
\layout Itemize

The <for body> does not contain 
\begin_inset Quotes eld
\end_inset 

continue
\begin_inset Quotes erd
\end_inset 

 or 'break
\begin_inset Quotes erd
\end_inset 

.
\layout Itemize

All goto's are contained within the loop.
\layout Itemize

No function calls within the loop.
\layout Itemize

The loop control variable <sym> is not assigned any value within the loop
\layout Itemize

The loop control variable does NOT participate in any arithmetic operation
 within the loop.
\layout Itemize

There are NO switch statements in the loop.
\layout Subsubsection

Algebraic Simplifications
\layout Standard

SDCC does numerous algebraic simplifications, the following is a small sub-set
 of these optimizations.
\newline 

\newline 

\family typewriter 
i = j + 0 ; /* changed to */ i = j; 
\newline 
i /= 2; /* changed to */ i >>= 1; 
\newline 
i = j - j ; /* changed to */ i = 0; 
\newline 
i = j / 1 ; /* changed to */ i = j;
\family default 

\newline 

\newline 
Note the subexpressions given above are generally introduced by macro expansions
 or as a result of copy/constant propagation.
\layout Subsubsection

'switch' Statements
\layout Standard

SDCC changes switch statements to jump tables when the following conditions
 are true.
 
\layout Itemize

The case labels are in numerical sequence, the labels need not be in order,
 and the starting number need not be one or zero.
\newline 

\newline 

\family typewriter 
switch(i) {\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
switch (i) { 
\newline 
case 4:...
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
case 1: ...
 
\newline 
case 5:...
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
case 2: ...
 
\newline 
case 3:...
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
case 3: ...
 
\newline 
case 6:...
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
case 4: ...
 
\newline 
}\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
}
\newline 

\newline 

\family default 
Both the above switch statements will be implemented using a jump-table.
\layout Itemize

The number of case labels is at least three, since it takes two conditional
 statements to handle the boundary conditions.
\layout Itemize

The number of case labels is less than 84, since each label takes 3 bytes
 and a jump-table can be utmost 256 bytes long.
 
\layout Standard

Switch statements which have gaps in the numeric sequence or those that
 have more that 84 case labels can be split into more than one switch statement
 for efficient code generation, e.g.:
\newline 

\newline 

\family typewriter 
switch (i) { 
\newline 
case 1: ...
 
\newline 
case 2: ...
 
\newline 
case 3: ...
 
\newline 
case 4: ...
 
\newline 
case 9: ...
 
\newline 
case 10: ...
 
\newline 
case 11: ...
 
\newline 
case 12: ...
 
\newline 
}
\family default 

\newline 

\newline 
If the above switch statement is broken down into two switch statements
\newline 

\newline 

\family typewriter 
switch (i) { 
\newline 
case 1: ...
 
\newline 
case 2: ...
 
\newline 
case 3: ...
 
\newline 
case 4: ...
 
\newline 
}
\newline 

\newline 

\family default 
and
\family typewriter 

\newline 

\newline 
switch (i) { 
\newline 
case 9: \SpecialChar ~
...
 
\newline 
case 10: ...
 
\newline 
case 11: ...
 
\newline 
case 12:\SpecialChar ~
...
 
\newline 
}
\newline 

\newline 

\family default 
then both the switch statements will be implemented using jump-tables whereas
 the unmodified switch statement will not be.
\layout Subsubsection

Bit-shifting Operations.
\layout Standard

Bit shifting is one of the most frequently used operation in embedded programmin
g.
 SDCC tries to implement bit-shift operations in the most efficient way
 possible, e.g.:
\newline 

\family typewriter 

\newline 
unsigned char i;
\newline 
...
 
\newline 
i>>= 4; 
\newline 
...
\newline 

\family default 

\newline 
generates the following code:
\newline 

\family typewriter 

\newline 
mov a,_i 
\newline 
swap a 
\newline 
anl a,#0x0f 
\newline 
mov _i,a
\family default 

\newline 

\newline 
In general SDCC will never setup a loop if the shift count is known.
 Another example:
\newline 

\newline 

\family typewriter 
unsigned int i; 
\newline 
...
 
\newline 
i >>= 9; 
\newline 
...
\family default 

\newline 

\newline 
will generate:
\newline 

\newline 

\family typewriter 
mov a,(_i + 1) 
\newline 
mov (_i + 1),#0x00 
\newline 
clr c 
\newline 
rrc a 
\newline 
mov _i,a
\family default 

\newline 

\newline 
Note that SDCC stores numbers in little-endian format (i.e.
 lowest order first).
\layout Subsubsection

Bit-rotation
\layout Standard

A special case of the bit-shift operation is bit rotation, SDCC recognizes
 the following expression to be a left bit-rotation:
\newline 

\newline 

\family typewriter 
unsigned char i; 
\newline 
...
 
\newline 
i = ((i << 1) | (i >> 7)); 
\family default 

\newline 
...
\newline 

\newline 
will generate the following code:
\newline 

\newline 

\family typewriter 
mov a,_i 
\newline 
rl a 
\newline 
mov _i,a
\family default 

\newline 

\newline 
SDCC uses pattern matching on the parse tree to determine this operation.Variatio
ns of this case will also be recognized as bit-rotation, i.e.: 
\newline 

\newline 

\family typewriter 
i = ((i >> 7) | (i << 1)); /* left-bit rotation */
\layout Subsubsection

Highest Order Bit
\layout Standard

It is frequently required to obtain the highest order bit of an integral
 type (long, int, short or char types).
 SDCC recognizes the following expression to yield the highest order bit
 and generates optimized code for it, e.g.:
\newline 

\newline 
 
\family typewriter 
unsigned int gint; 
\newline 

\newline 
foo () { 
\newline 
unsigned char hob; 
\newline 
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
\SpecialChar ~
\SpecialChar ~
hob = (gint >> 15) & 1; 
\newline 
\SpecialChar ~
\SpecialChar ~
..
 
\newline 
}
\family default 

\newline 

\newline 
will generate the following code:
\newline 

\family typewriter 

\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 61 ;\SpecialChar ~
 hob.c 7 
\newline 
\SpecialChar ~
\SpecialChar ~
 000A E5*01\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 62\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 mov\SpecialChar ~
 a,(_gint + 1) 
\newline 
\SpecialChar ~
\SpecialChar ~
 000C 33\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 63\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 rlc\SpecialChar ~
 a 
\newline 
\SpecialChar ~
\SpecialChar ~
 000D E4\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 64\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 clr\SpecialChar ~
 a 
\newline 
\SpecialChar ~
\SpecialChar ~
 000E 13\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 65\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 rrc\SpecialChar ~
 a 
\newline 
\SpecialChar ~
\SpecialChar ~
 000F F5*02\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 66\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 mov\SpecialChar ~
 _foo_hob_1_1,a
\newline 

\newline 

\family default 
Variations of this case however will 
\emph on 
not
\emph default 
 be recognized.
 It is a standard C expression, so I heartily recommend this be the only
 way to get the highest order bit, (it is portable).
 Of course it will be recognized even if it is embedded in other expressions,
 e.g.:
\newline 

\newline 

\family typewriter 
xyz = gint + ((gint >> 15) & 1);
\family default 

\newline 

\newline 
will still be recognized.
\layout Subsubsection

Peep-hole Optimizer
\layout Standard

The compiler uses a rule based, pattern matching and re-writing mechanism
 for peep-hole optimization.
 It is inspired by 
\emph on 
copt
\emph default 
 a peep-hole optimizer by Christopher W.
 Fraser (cwfraser@microsoft.com).
 A default set of rules are compiled into the compiler, additional rules
 may be added with the 
\emph on 
--peep-file <filename>
\emph default 
 option.
 The rule language is best illustrated with examples.
\newline 

\newline 

\family typewriter 
replace { 
\newline 
\SpecialChar ~
\SpecialChar ~
mov %1,a 
\newline 
\SpecialChar ~
\SpecialChar ~
mov a,%1
\newline 
} by {
\newline 
\SpecialChar ~
\SpecialChar ~
mov %1,a
\newline 
}
\family default 

\newline 

\newline 
The above rule will change the following assembly sequence:
\newline 

\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
mov r1,a 
\newline 
\SpecialChar ~
\SpecialChar ~
mov a,r1
\family default 

\newline 

\newline 
to
\newline 

\newline 

\family typewriter 
mov r1,a
\family default 

\newline 

\newline 
Note: All occurrences of a 
\emph on 
%n
\emph default 
 (pattern variable) must denote the same string.
 With the above rule, the assembly sequence:
\newline 

\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
mov r1,a 
\newline 
\SpecialChar ~
\SpecialChar ~
mov a,r2
\family default 

\newline 

\newline 
will remain unmodified.
\newline 

\newline 
Other special case optimizations may be added by the user (via 
\emph on 
--peep-file option
\emph default 
).
 E.g.
 some variants of the 8051 MCU allow only 
\family typewriter 
ajmp
\family default 
 and 
\family typewriter 
acall
\family default 
.
 The following two rules will change all 
\family typewriter 
ljmp
\family default 
 and 
\family typewriter 
lcall
\family default 
 to 
\family typewriter 
ajmp
\family default 
 and 
\family typewriter 
acall
\family default 

\newline 

\newline 

\family typewriter 
replace { lcall %1 } by { acall %1 } 
\newline 
replace { ljmp %1 } by { ajmp %1 }
\family default 

\newline 

\newline 
The 
\emph on 
inline-assembler code
\emph default 
 is also passed through the peep hole optimizer, thus the peephole optimizer
 can also be used as an assembly level macro expander.
 The rules themselves are MCU dependent whereas the rule language infra-structur
e is MCU independent.
 Peephole optimization rules for other MCU can be easily programmed using
 the rule language.
\newline 

\newline 
The syntax for a rule is as follows:
\newline 

\newline 

\family typewriter 
rule := replace [ restart ] '{' <assembly sequence> '
\backslash 
n' 
\newline 
\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 '}' by '{' '
\backslash 
n' 
\newline 
\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 <assembly sequence> '
\backslash 
n' 
\newline 
\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
 '}' [if <functionName> ] '
\backslash 
n' 
\newline 

\family default 

\newline 
<assembly sequence> := assembly instruction (each instruction including
 labels must be on a separate line).
\newline 

\newline 
The optimizer will apply to the rules one by one from the top in the sequence
 of their appearance, it will terminate when all rules are exhausted.
 If the 'restart' option is specified, then the optimizer will start matching
 the rules again from the top, this option for a rule is expensive (performance)
, it is intended to be used in situations where a transformation will trigger
 the same rule again.
 An example of this (not a good one, it has side effects) is the following
 rule:
\newline 

\newline 

\family typewriter 
replace restart { 
\newline 
\SpecialChar ~
\SpecialChar ~
pop %1 
\newline 
\SpecialChar ~
\SpecialChar ~
push %1 } by { 
\newline 
\SpecialChar ~
\SpecialChar ~
; nop 
\newline 
}
\family default 

\newline 

\newline 
Note that the replace pattern cannot be a blank, but can be a comment line.
 Without the 'restart' option only the inner most 'pop' 'push' pair would
 be eliminated, i.e.:
\newline 

\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
pop ar1 
\newline 
\SpecialChar ~
\SpecialChar ~
pop ar2 
\newline 
\SpecialChar ~
\SpecialChar ~
push ar2 
\newline 
\SpecialChar ~
\SpecialChar ~
push ar1
\family default 

\newline 

\newline 
would result in:
\newline 

\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
pop ar1 
\newline 
\SpecialChar ~
\SpecialChar ~
; nop 
\newline 
\SpecialChar ~
\SpecialChar ~
push ar1
\family default 

\newline 

\newline 

\emph on 
with
\emph default 
 the restart option the rule will be applied again to the resulting code
 and then all the pop-push pairs will be eliminated to yield:
\newline 

\newline 

\family typewriter 
\SpecialChar ~
\SpecialChar ~
; nop 
\newline 
\SpecialChar ~
\SpecialChar ~
; nop
\family default 

\newline 

\newline 
A conditional function can be attached to a rule.
 Attaching rules are somewhat more involved, let me illustrate this with
 an example.
\newline 

\newline 

\family typewriter 
replace { 
\newline 
\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
ljmp %5 
\newline 
%2:
\newline 
} by { 
\newline 
\SpecialChar ~
 \SpecialChar ~
 \SpecialChar ~
sjmp %5 
\newline 
%2:
\newline 
} if labelInRange
\family default 

\newline 

\newline 
The optimizer does a look-up of a function name table defined in function
 
\emph on 
callFuncByName
\emph default 
 in the source file SDCCpeeph.c, with the name 
\emph on 
labelInRange
\emph default 
.
 If it finds a corresponding entry the function is called.
 Note there can be no parameters specified for these functions, in this
 case the use of 
\emph on 
%5
\emph default 
 is crucial, since the function 
\emph on 
labelInRange
\emph default 
 expects to find the label in that particular variable (the hash table containin
g the variable bindings is passed as a parameter).
 If you want to code more such functions, take a close look at the function
 labelInRange and the calling mechanism in source file SDCCpeeph.c.
 I know this whole thing is a little kludgey, but maybe some day we will
 have some better means.
 If you are looking at this file, you will also see the default rules that
 are compiled into the compiler, you can add your own rules in the default
 set there if you get tired of specifying the --peep-file option.
\layout Subsection

Pragmas
\layout Standard

SDCC supports the following #pragma directives.
 This directives are applicable only at a function level.
\layout Itemize

SAVE - this will save all the current options.
\layout Itemize

RESTORE - will restore the saved options from the last save.
 Note that SAVES & RESTOREs cannot be nested.
 SDCC uses the same buffer to save the options each time a SAVE is called.
\layout Itemize

NOGCSE - will stop global subexpression elimination.
\layout Itemize

NOINDUCTION - will stop loop induction optimizations.
\layout Itemize

NOJTBOUND - will not generate code for boundary value checking, when switch
 statements are turned into jump-tables.
\layout Itemize

NOOVERLAY - the compiler will not overlay the parameters and local variables
 of a function.
\layout Itemize

NOLOOPREVERSE - Will not do loop reversal optimization
\layout Itemize

EXCLUDE NONE | {acc[,b[,dpl[,dph]]] - The exclude pragma disables generation
 of pair of push/pop instruction in ISR function (using interrupt keyword).
 The directive should be placed immediately before the ISR function definition
 and it affects ALL ISR functions following it.
 To enable the normal register saving for ISR functions use #pragma\SpecialChar ~
EXCLUDE\SpecialChar ~
none.
\layout Itemize

CALLEE-SAVES function1[,function2[,function3...]] - The compiler by default
 uses a caller saves convention for register saving across function calls,
 however this can cause unneccessary register pushing & popping when calling
 small functions from larger functions.
 This option can be used to switch the register saving convention for the
 function names specified.
 The compiler will not save registers when calling these functions, extra
 code will be generated at the entry & exit for these functions to save
 & restore the registers used by these functions, this can SUBSTANTIALLY
 reduce code & improve run time performance of the generated code.
 In future the compiler (with interprocedural analysis) will be able to
 determine the appropriate scheme to use for each function call.
 If --callee-saves command line option is used, the function names specified
 in #pragma\SpecialChar ~
CALLEE-SAVES is appended to the list of functions specified inthe
 command line.
\layout Standard

The pragma's are intended to be used to turn-off certain optimizations which
 might cause the compiler to generate extra stack / data space to store
 compiler generated temporary variables.
 This usually happens in large functions.
 Pragma directives should be used as shown in the following example, they
 are used to control options & optimizations for a given function; pragmas
 should be placed before and/or after a function, placing pragma's inside
 a function body could have unpredictable results.
\newline 

\newline 

\family typewriter 
#pragma SAVE /* save the current settings */ 
\newline 
#pragma NOGCSE /* turnoff global subexpression elimination */ 
\newline 
#pragma NOINDUCTION /* turn off induction optimizations */ 
\newline 
int foo () 
\newline 
{ 
\newline 
\SpecialChar ~
 \SpecialChar ~
 ...
 
\newline 
\SpecialChar ~
 \SpecialChar ~
 /* large code */ 
\newline 
\SpecialChar ~
 \SpecialChar ~
 ...
 
\newline 
} 
\newline 
#pragma RESTORE /* turn the optimizations back on */
\family default 

\newline 

\newline 
The compiler will generate a warning message when extra space is allocated.
 It is strongly recommended that the SAVE and RESTORE pragma's be used when
 changing options for a function.
\layout Subsection


\emph on 
<pending: this is messy and incomplete>
\emph default 
 Library Routines
\layout Standard

The following library routines are provided for your convenience.
\layout Standard

stdio.h - Contains the following functions printf & sprintf these routines
 are developed by Martijn van Balen <balen@natlab.research.philips.com>.
 
\layout Standard

%[flags][width][b|B|l|L]type
\layout Standard

\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 flags: -\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 left justify output in specified field width 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 +\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 prefix output with +/- sign if output is signed type 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 space\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 prefix output with a blank if it's a signed positive value 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 width:\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 specifies minimum number of characters outputted for numbers 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 or strings.
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 - For numbers, spaces are added on the left when needed.
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 If width starts with a zero character, zeroes and used 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 instead of spaces.
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 - For strings, spaces are are added on the left or right (when 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 flag '-' is used) when needed.
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 b/B:\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 byte argument (used by d, u, o, x, X) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 l/L:\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 long argument (used by d, u, o, x, X)
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 type:\SpecialChar ~
 d\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 decimal number 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 u\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned decimal number 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 o\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned octal number 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 x\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned hexadecimal number (0-9, a-f) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 X\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned hexadecimal number (0-9, A-F) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 c\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 character 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 s\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 string (generic pointer) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 p\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 generic pointer (I:data/idata, C:code, X:xdata, P:paged) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 f\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 float (still to be implemented)
\layout Standard

Also contains a very simple version of printf (printf_small).
 This simplified version of printf supports only the following formats.
\layout Standard

format\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
output\SpecialChar ~
type\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
argument-type 
\newline 
%d \SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
decimal \SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 short/int 
\newline 
%ld\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
decimal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
long 
\newline 
%hd\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
decimal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
char 
\newline 
%x\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
hexadecimal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
short/int 
\newline 
%lx\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
hexadecimal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
long 
\newline 
%hx\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
hexadecimal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
char 
\newline 
%o\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
octal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
short/int 
\newline 
%lo\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
octal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
long 
\newline 
%ho\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
octal\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
char 
\newline 
%c\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
character\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
char 
\newline 
%s\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
character\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
_generic pointer
\layout Standard

The routine is very stack intesive, --stack-after-data parameter should
 be used when using this routine, the routine also takes about 1K of code
 space.
 It also expects an external function named putchar(char) to be present
 (this can be changed).
 When using the %s format the string / pointer should be cast to a generic
 pointer.
 eg.
\layout Standard

printf_small(
\begin_inset Quotes eld
\end_inset 

my str %s, my int %d
\backslash 
n
\begin_inset Quotes erd
\end_inset 

,(char _generic *)mystr,myint);
\layout Itemize

stdarg.h - contains definition for the following macros to be used for variable
 parameter list, note that a function can have a variable parameter list
 if and only if it is 'reentrant'
\begin_deeper 
\layout Standard

va_list, va_start, va_arg, va_end.
\end_deeper 
\layout Itemize

setjmp.h - contains defintion for ANSI setjmp & longjmp routines.
 Note in this case setjmp & longjmp can be used between functions executing
 within the same register bank, if long jmp is executed from a function
 that is using a different register bank from the function issuing the setjmp
 function, the results may be unpredictable.
 The jump buffer requires 3 bytes of data (the stack pointer & a 16 byte
 return address), and can be placed in any address space.
\layout Itemize

stdlib.h - contains the following functions.
\begin_deeper 
\layout Standard

atoi, atol.
\end_deeper 
\layout Itemize

string.h - contains the following functions.
\begin_deeper 
\layout Standard

strcpy, strncpy, strcat, strncat, strcmp, strncmp, strchr, strrchr, strspn,
 strcspn, strpbrk, strstr, strlen, strtok, memcpy, memcmp, memset.
\end_deeper 
\layout Itemize

ctype.h - contains the following routines.
\begin_deeper 
\layout Standard

iscntrl, isdigit, isgraph, islower, isupper, isprint, ispunct, isspace,
 isxdigit, isalnum, isalpha.
\end_deeper 
\layout Itemize

malloc.h - The malloc routines are developed by Dmitry S.
 Obukhov (dso@usa.net).
 These routines will allocate memory from the external ram.
 Here is a description on how to use them (as described by the author).
\begin_deeper 
\layout Standard

//Example: 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 #define DYNAMIC_MEMORY_SIZE 0x2000 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 .....
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned char xdata dynamic_memory_pool[DYNAMIC_MEMORY_SIZE]; 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 unsigned char xdata * current_buffer; 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 .....
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 void main(void) 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 { 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 ...
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
//\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 init_dynamic_memory(dynamic_memory_pool,DYNAMIC_MEMORY_SIZE); 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //Now it's possible to use malloc.
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 ...
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 current_buffer = malloc(0x100); 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 //
\end_deeper 
\layout Itemize

serial.h - Serial IO routines are also developed by Dmitry S.
 Obukhov (dso@usa.net).
 These routines are interrupt driven with a 256 byte circular buffer, they
 also expect external ram to be present.
 Please see documentation in file SDCCDIR/sdcc51lib/serial.c.
 Note the header file 
\begin_inset Quotes eld
\end_inset 

serial.h
\begin_inset Quotes erd
\end_inset 

 MUST be included in the file containing the 'main' function.
\layout Itemize

ser.h - Alternate serial routine provided by Wolfgang Esslinger <wolfgang@WiredMi
nds.com> these routines are more compact and faster.
 Please see documentation in file SDCCDIR/sdcc51lib/ser.c
\layout Itemize

ser_ir.h - Another alternate set of serial routines provided by Josef Wolf
 <jw@raven.inka.de>, these routines do not use the external ram.
\layout Itemize

reg51.h - contains register definitions for a standard 8051
\layout Itemize

float.h - contains min, max and other floating point related stuff.
\layout Standard

All library routines are compiled as --model-small, they are all non-reentrant,
 if you plan to use the large model or want to make these routines reentrant,
 then they will have to be recompiled with the appropriate compiler option.
\layout Standard

Have not had time to do the more involved routines like printf, will get
 to them shortly.
\layout Subsection

Interfacing with Assembly Routines
\layout Subsubsection

Global Registers used for Parameter Passing
\layout Standard

The compiler always uses the global registers 
\emph on 
DPL,DPH,B 
\emph default 
and
\emph on 
 ACC
\emph default 
 to pass the first parameter to a routine.
 The second parameter onwards is either allocated on the stack (for reentrant
 routines or if --stack-auto is used) or in the internal / external ram
 (depending on the memory model).
 
\layout Subsubsection

Assembler Routine(non-reentrant)
\layout Standard

In the following example the function cfunc calls an assembler routine asm_func,
 which takes two parameters.
\newline 

\newline 

\family typewriter 
extern int asm_func(unsigned char, unsigned char);
\newline 

\newline 
int c_func (unsigned char i, unsigned char j)
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return asm_func(i,j);
\newline 
}
\newline 

\newline 
int main()
\newline 
{
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return c_func(10,9);
\newline 
}
\newline 

\newline 

\family default 
The corresponding assembler function is:
\newline 

\newline 

\family typewriter 
.globl _asm_func_PARM_2 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
.globl _asm_func 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
.area OSEG 
\newline 
_asm_func_PARM_2:
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
.ds      1 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
.area CSEG 
\newline 
_asm_func: 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov     a,dpl 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
add     a,_asm_func_PARM_2 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov     dpl,a 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov     dpl,#0x00 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
ret
\newline 

\newline 

\family default 
Note here that the return values are placed in 'dpl' - One byte return value,
 'dpl' LSB & 'dph' MSB for two byte values.
 'dpl', 'dph' and 'b' for three byte values (generic pointers) and 'dpl','dph','
b' & 'acc' for four byte values.
\layout Standard

The parameter naming convention is _<function_name>_PARM_<n>, where n is
 the parameter number starting from 1, and counting from the left.
 The first parameter is passed in 
\begin_inset Quotes eld
\end_inset 

dpl
\begin_inset Quotes erd
\end_inset 

 for One bye parameter, 
\begin_inset Quotes eld
\end_inset 

dptr
\begin_inset Quotes erd
\end_inset 

 if two bytes, 
\begin_inset Quotes eld
\end_inset 

b,dptr
\begin_inset Quotes erd
\end_inset 

 for three bytes and 
\begin_inset Quotes eld
\end_inset 

acc,b,dptr
\begin_inset Quotes erd
\end_inset 

 for four bytes, the varible name for the second parameter will be _<function_na
me>_PARM_2.
\newline 

\newline 
Assemble the assembler routine with the following command:
\newline 

\newline 

\family sans 
\series bold 
asx8051 -losg asmfunc.asm
\newline 

\newline 

\family default 
\series default 
Then compile and link the assembler routine to the C source file with the
 following command:
\newline 

\newline 

\family sans 
\series bold 
sdcc cfunc.c asmfunc.rel
\layout Subsubsection

Assembler Routine(reentrant)
\layout Standard

In this case the second parameter onwards will be passed on the stack, the
 parameters are pushed from right to left i.e.
 after the call the left most parameter will be on the top of the stack.
 Here is an example:
\newline 

\newline 

\family typewriter 
extern int asm_func(unsigned char, unsigned char);
\newline 

\newline 
int c_func (unsigned char i, unsigned char j) reentrant 
\newline 
{ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return asm_func(i,j); 
\newline 
} 
\newline 

\newline 
int main() 
\newline 
{ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return c_func(10,9); 
\newline 
}
\newline 

\family default 

\newline 
The corresponding assembler routine is:
\newline 

\newline 

\family typewriter 
.globl _asm_func 
\newline 
_asm_func: 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
push  _bp 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  _bp,sp 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  r2,dpl
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  a,_bp 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
clr  c 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
add  a,#0xfd 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  r0,a 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
add  a,#0xfc
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  r1,a 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  a,@r0 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
add  a,r2
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  dpl,a 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  dph,#0x00 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
mov  sp,_bp 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
pop  _bp 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
ret
\newline 

\newline 

\family default 
The compiling and linking procedure remains the same, however note the extra
 entry & exit linkage required for the assembler code, _bp is the stack
 frame pointer and is used to compute the offset into the stack for parameters
 and local variables.
\layout Subsection

External Stack
\layout Standard

The external stack is located at the start of the external ram segment,
 and is 256 bytes in size.
 When --xstack option is used to compile the program, the parameters and
 local variables of all reentrant functions are allocated in this area.
 This option is provided for programs with large stack space requirements.
 When used with the --stack-auto option, all parameters and local variables
 are allocated on the external stack (note support libraries will need to
 be recompiled with the same options).
\layout Standard

The compiler outputs the higher order address byte of the external ram segment
 into PORT P2, therefore when using the External Stack option, this port
 MAY NOT be used by the application program.
\layout Subsection

ANSI-Compliance
\layout Standard

Deviations from the compliancy.
\layout Itemize

functions are not always reentrant.
\layout Itemize

structures cannot be assigned values directly, cannot be passed as function
 parameters or assigned to each other and cannot be a return value from
 a function, e.g.:
\family typewriter 

\newline 

\newline 
struct s { ...
 }; 
\newline 
struct s s1, s2; 
\newline 
foo() 
\newline 
{ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
s1 = s2 ; /* is invalid in SDCC although allowed in ANSI */ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
}
\newline 
struct s foo1 (struct s parms) /* is invalid in SDCC although allowed in
 ANSI */ 
\newline 
{ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
struct s rets; 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
return rets;/* is invalid in SDCC although allowed in ANSI */ 
\newline 
}
\layout Itemize

'long long' (64 bit integers) not supported.
\layout Itemize

'double' precision floating point not supported.
\layout Itemize

No support for setjmp and longjmp (for now).
\layout Itemize

Old K&R style function declarations are NOT allowed.
\newline 

\family typewriter 

\newline 
foo(i,j) /* this old style of function declarations */ 
\newline 
int i,j; /* are valid in ANSI but not valid in SDCC */ 
\newline 
{ 
\newline 
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
...
 
\newline 
}
\layout Itemize

functions declared as pointers must be dereferenced during the call.
\newline 

\family typewriter 

\newline 
int (*foo)();
\newline 
...
 
\newline 
/* has to be called like this */ 
\newline 
(*foo)(); /* ansi standard allows calls to be made like 'foo()' */
\layout Subsection

Cyclomatic Complexity
\layout Standard

Cyclomatic complexity of a function is defined as the number of independent
 paths the program can take during execution of the function.
 This is an important number since it defines the number test cases you
 have to generate to validate the function.
 The accepted industry standard for complexity number is 10, if the cyclomatic
 complexity reported by SDCC exceeds 10 you should think about simplification
 of the function logic.
 Note that the complexity level is not related to the number of lines of
 code in a function.
 Large functions can have low complexity, and small functions can have large
 complexity levels.
 
\newline 

\newline 
SDCC uses the following formula to compute the complexity:
\newline 

\layout Standard

complexity = (number of edges in control flow graph) - (number of nodes
 in control flow graph) + 2;
\newline 

\newline 
Having said that the industry standard is 10, you should be aware that in
 some cases it be may unavoidable to have a complexity level of less than
 10.
 For example if you have switch statement with more than 10 case labels,
 each case label adds one to the complexity level.
 The complexity level is by no means an absolute measure of the algorithmic
 complexity of the function, it does however provide a good starting point
 for which functions you might look at for further optimization.
\layout Section

TIPS
\layout Standard

Here are a few guidelines that will help the compiler generate more efficient
 code, some of the tips are specific to this compiler others are generally
 good programming practice.
\layout Itemize

Use the smallest data type to represent your data-value.
 If it is known in advance that the value is going to be less than 256 then
 use a 'char' instead of a 'short' or 'int'.
\layout Itemize

Use unsigned when it is known in advance that the value is not going to
 be negative.
 This helps especially if you are doing division or multiplication.
\layout Itemize

NEVER jump into a LOOP.
\layout Itemize

Declare the variables to be local whenever possible, especially loop control
 variables (induction).
\layout Itemize

Since the compiler does not do implicit integral promotion, the programmer
 should do an explicit cast when integral promotion is required.
\layout Itemize

Reducing the size of division, multiplication & modulus operations can reduce
 code size substantially.
 Take the following code for example.
\family typewriter 

\newline 

\newline 
foobar(unsigned int p1, unsigned char ch)
\newline 
{
\newline 
    unsigned char ch1 = p1 % ch ;
\newline 
    ....
    
\newline 
}
\newline 

\family default 

\newline 
For the modulus operation the variable ch will be promoted to unsigned int
 first then the modulus operation will be performed (this will lead to a
 call to support routine _muduint()), and the result will be casted to an
 int.
 If the code is changed to 
\newline 

\family typewriter 

\newline 
foobar(unsigned int p1, unsigned char ch)
\newline 
{
\newline 
    unsigned char ch1 = (unsigned char)p1 % ch ;
\newline 
    ....
    
\newline 
}
\newline 

\family default 

\newline 
It would substantially reduce the code generated (future versions of the
 compiler will be smart enough to detect such optimization oppurtunities).
\layout Subsection

Notes on MCS51 memory layout
\layout Standard

The 8051 family of micro controller have a minimum of 128 bytes of internal
 memory which is structured as follows
\newline 

\newline 
- Bytes 00-1F - 32 bytes to hold up to 4 banks of the registers R7 to R7
 
\newline 
- Bytes 20-2F - 16 bytes to hold 128 bit variables and 
\newline 
- Bytes 30-7F - 60 bytes for general purpose use.
\newline 

\newline 
Normally the SDCC compiler will only utilise the first bank of registers,
 but it is possible to specify that other banks of registers should be used
 in interrupt routines.
 By default, the compiler will place the stack after the last bank of used
 registers, i.e.
 if the first 2 banks of registers are used, it will position the base of
 the internal stack at address 16 (0X10).
 This implies that as the stack grows, it will use up the remaining register
 banks, and the 16 bytes used by the 128 bit variables, and 60 bytes for
 general purpose use.
\layout Standard

By default, the compiler uses the 60 general purpose bytes to hold "near
 data".
 The compiler/optimiser may also declare some Local Variables in this area
 to hold local data.
 
\layout Standard

If any of the 128 bit variables are used, or near data is being used then
 care needs to be taken to ensure that the stack does not grow so much that
 it starts to over write either your bit variables or "near data".
 There is no runtime checking to prevent this from happening.
\layout Standard

The amount of stack being used is affected by the use of the "internal stack"
 to save registers before a subroutine call is made (--stack-auto will declare
 parameters and local variables on the stack) and the number of nested subroutin
es.
\layout Standard

If you detect that the stack is over writing you data, then the following
 can be done.
 --xstack will cause an external stack to be used for saving registers and
 (if --stack-auto is being used) storing parameters and local variables.
 However this will produce more code which will be slower to execute.
 
\layout Standard

--stack-loc will allow you specify the start of the stack, i.e.
 you could start it after any data in the general purpose area.
 However this may waste the memory not used by the register banks and if
 the size of the "near data" increases, it may creep into the bottom of
 the stack.
\layout Standard

--stack-after-data, similar to the --stack-loc, but it automatically places
 the stack after the end of the "near data".
 Again this could waste any spare register space.
\layout Standard

--data-loc allows you to specify the start address of the near data.
 This could be used to move the "near data" further away from the stack
 giving it more room to grow.
 This will only work if no bit variables are being used and the stack can
 grow to use the bit variable space.
\newline 

\newline 
Conclusion.
\newline 

\newline 
If you find that the stack is over writing your bit variables or "near data"
 then the approach which best utilised the internal memory is to position
 the "near data" after the last bank of used registers or, if you use bit
 variables, after the last bit variable by using the --data-loc, e.g.
 if two register banks are being used and no bit variables, --data-loc 16,
 and use the --stack-after-data option.
\layout Standard

If bit variables are being used, another method would be to try and squeeze
 the data area in the unused register banks if it will fit, and start the
 stack after the last bit variable.
\layout Section

Retargetting for other MCUs.
\layout Standard

The issues for retargetting the compiler are far too numerous to be covered
 by this document.
 What follows is a brief description of each of the seven phases of the
 compiler and its MCU dependency.
\layout Itemize

Parsing the source and building the annotated parse tree.
 This phase is largely MCU independent (except for the language extensions).
 Syntax & semantic checks are also done in this phase, along with some initial
 optimizations like back patching labels and the pattern matching optimizations
 like bit-rotation etc.
\layout Itemize

The second phase involves generating an intermediate code which can be easy
 manipulated during the later phases.
 This phase is entirely MCU independent.
 The intermediate code generation assumes the target machine has unlimited
 number of registers, and designates them with the name iTemp.
 The compiler can be made to dump a human readable form of the code generated
 by using the --dumpraw option.
\layout Itemize

This phase does the bulk of the standard optimizations and is also MCU independe
nt.
 This phase can be broken down into several sub-phases:
\newline 

\newline 
Break down intermediate code (iCode) into basic blocks.
\newline 
Do control flow & data flow analysis on the basic blocks.
\newline 
Do local common subexpression elimination, then global subexpression elimination
\newline 
Dead code elimination
\newline 
Loop optimizations
\newline 
If loop optimizations caused any changes then do 'global subexpression eliminati
on' and 'dead code elimination' again.
\layout Itemize

This phase determines the live-ranges; by live range I mean those iTemp
 variables defined by the compiler that still survive after all the optimization
s.
 Live range analysis is essential for register allocation, since these computati
on determines which of these iTemps will be assigned to registers, and for
 how long.
\layout Itemize

Phase five is register allocation.
 There are two parts to this process.
\newline 

\newline 
The first part I call 'register packing' (for lack of a better term).
 In this case several MCU specific expression folding is done to reduce
 register pressure.
\newline 

\newline 
The second part is more MCU independent and deals with allocating registers
 to the remaining live ranges.
 A lot of MCU specific code does creep into this phase because of the limited
 number of index registers available in the 8051.
\layout Itemize

The Code generation phase is (unhappily), entirely MCU dependent and very
 little (if any at all) of this code can be reused for other MCU.
 However the scheme for allocating a homogenized assembler operand for each
 iCode operand may be reused.
\layout Itemize

As mentioned in the optimization section the peep-hole optimizer is rule
 based system, which can reprogrammed for other MCUs.
\layout Section

SDCDB - Source Level Debugger
\layout Standard

SDCC is distributed with a source level debugger.
 The debugger uses a command line interface, the command repertoire of the
 debugger has been kept as close to gdb (the GNU debugger) as possible.
 The configuration and build process is part of the standard compiler installati
on, which also builds and installs the debugger in the target directory
 specified during configuration.
 The debugger allows you debug BOTH at the C source and at the ASM source
 level.
\layout Subsection

Compiling for Debugging
\layout Standard

The \SpecialChar \-
\SpecialChar \-
debug option must be specified for all files for which debug information
 is to be generated.
 The complier generates a .cdb file for each of these files.
 The linker updates the .cdb file with the address information.
 This .cdb is used by the debugger.
\layout Subsection

How the Debugger Works
\layout Standard

When the --debug option is specified the compiler generates extra symbol
 information some of which are put into the the assembler source and some
 are put into the .cdb file, the linker updates the .cdb file with the address
 information for the symbols.
 The debugger reads the symbolic information generated by the compiler &
 the address information generated by the linker.
 It uses the SIMULATOR (Daniel's S51) to execute the program, the program
 execution is controlled by the debugger.
 When a command is issued for the debugger, it translates it into appropriate
 commands for the simulator.
\layout Subsection

Starting the Debugger
\layout Standard

The debugger can be started using the following command line.
 (Assume the file you are debugging has the file name foo).
\newline 

\newline 

\family sans 
\series bold 
sdcdb foo
\newline 

\family default 
\series default 

\newline 
The debugger will look for the following files.
\layout Itemize

foo.c - the source file.
\layout Itemize

foo.cdb - the debugger symbol information file.
\layout Itemize

foo.ihx - the intel hex format object file.
\layout Subsection

Command Line Options.
\layout Itemize

--directory=<source file directory> this option can used to specify the
 directory search list.
 The debugger will look into the directory list specified for source, cdb
 & ihx files.
 The items in the directory list must be separated by ':', e.g.
 if the source files can be in the directories /home/src1 and /home/src2,
 the --directory option should be --directory=/home/src1:/home/src2.
 Note there can be no spaces in the option.
 
\layout Itemize

-cd <directory> - change to the <directory>.
\layout Itemize

-fullname - used by GUI front ends.
\layout Itemize

-cpu <cpu-type> - this argument is passed to the simulator please see the
 simulator docs for details.
\layout Itemize

-X <Clock frequency > this options is passed to the simulator please see
 the simulator docs for details.
\layout Itemize

-s <serial port file> passed to simulator see the simulator docs for details.
\layout Itemize

-S <serial in,out> passed to simulator see the simulator docs for details.
\layout Subsection

Debugger Commands.
\layout Standard

As mention earlier the command interface for the debugger has been deliberately
 kept as close the GNU debugger gdb, as possible.
 This will help the integration with existing graphical user interfaces
 (like ddd, xxgdb or xemacs) existing for the GNU debugger.
\layout Subsubsection

break [line | file:line | function | file:function]
\layout Standard

Set breakpoint at specified line or function:
\newline 

\newline 

\family sans 
\series bold 
sdcdb>break 100 
\newline 
sdcdb>break foo.c:100
\newline 
sdcdb>break funcfoo
\newline 
sdcdb>break foo.c:funcfoo
\layout Subsubsection

clear [line | file:line | function | file:function ]
\layout Standard

Clear breakpoint at specified line or function:
\newline 

\newline 

\family sans 
\series bold 
sdcdb>clear 100
\newline 
sdcdb>clear foo.c:100
\newline 
sdcdb>clear funcfoo
\newline 
sdcdb>clear foo.c:funcfoo
\layout Subsubsection

continue
\layout Standard

Continue program being debugged, after breakpoint.
\layout Subsubsection

finish
\layout Standard

Execute till the end of the current function.
\layout Subsubsection

delete [n]
\layout Standard

Delete breakpoint number 'n'.
 If used without any option clear ALL user defined break points.
\layout Subsubsection

info [break | stack | frame | registers ]
\layout Itemize

info break - list all breakpoints
\layout Itemize

info stack - show the function call stack.
\layout Itemize

info frame - show information about the current execution frame.
\layout Itemize

info registers - show content of all registers.
\layout Subsubsection

step
\layout Standard

Step program until it reaches a different source line.
\layout Subsubsection

next
\layout Standard

Step program, proceeding through subroutine calls.
\layout Subsubsection

run
\layout Standard

Start debugged program.
\layout Subsubsection

ptype variable 
\layout Standard

Print type information of the variable.
\layout Subsubsection

print variable
\layout Standard

print value of variable.
\layout Subsubsection

file filename
\layout Standard

load the given file name.
 Note this is an alternate method of loading file for debugging.
\layout Subsubsection

frame
\layout Standard

print information about current frame.
\layout Subsubsection

set srcmode
\layout Standard

Toggle between C source & assembly source.
\layout Subsubsection

! simulator command
\layout Standard

Send the string following '!' to the simulator, the simulator response is
 displayed.
 Note the debugger does not interpret the command being sent to the simulator,
 so if a command like 'go' is sent the debugger can loose its execution
 context and may display incorrect values.
\layout Subsubsection

quit.
\layout Standard

"Watch me now.
 Iam going Down.
 My name is Bobby Brown"
\layout Subsection

Interfacing with XEmacs.
\layout Standard

Two files (in emacs lisp) are provided for the interfacing with XEmacs,
 sdcdb.el and sdcdbsrc.el.
 These two files can be found in the $(prefix)/bin directory after the installat
ion is complete.
 These files need to be loaded into XEmacs for the interface to work.
 This can be done at XEmacs startup time by inserting the following into
 your '.xemacs' file (which can be found in your HOME directory): 
\newline 

\newline 

\family typewriter 
(load-file sdcdbsrc.el) 
\family default 

\newline 

\newline 
.xemacs is a lisp file so the () around the command is REQUIRED.
 The files can also be loaded dynamically while XEmacs is running, set the
 environment variable 'EMACSLOADPATH' to the installation bin directory
 (<installdir>/bin), then enter the following command ESC-x load-file sdcdbsrc.
 To start the interface enter the following command: 
\newline 

\newline 

\family sans 
\series bold 
ESC-x sdcdbsrc
\family default 
\series default 

\newline 

\newline 
You will prompted to enter the file name to be debugged.
 
\newline 

\newline 
The command line options that are passed to the simulator directly are bound
 to default values in the file sdcdbsrc.el.
 The variables are listed below, these values maybe changed as required.
\layout Itemize

sdcdbsrc-cpu-type '51
\layout Itemize

sdcdbsrc-frequency '11059200
\layout Itemize

sdcdbsrc-serial nil
\layout Standard

The following is a list of key mapping for the debugger interface.
\layout Standard

\SpecialChar ~

\family typewriter 

\newline 
;; Current Listing :: 
\newline 
;;key\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
binding\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Comment 
\newline 
;;---\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
-------\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
------- 
\newline 
;; 
\newline 
;; n\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-next-from-src\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB next command 
\newline 
;; b\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-back-from-src\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB back command 
\newline 
;; c\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-cont-from-src\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB continue command
\newline 
;; s\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-step-from-src\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB step command 
\newline 
;; ?\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-whatis-c-sexp\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB ptypecommand for data at 
\newline 
;;\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 buffer point 
\newline 
;; x\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-delete\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB Delete all breakpoints if no arg 
\newline 
;;\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
given or delete arg (C-u arg x) 
\newline 
;; m\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-frame\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB Display current frame if no arg, 
\newline 
;;\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
given or display frame arg 
\newline 
;;\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
buffer point 
\newline 
;; !\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-goto-sdcdb\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Goto the SDCDB output buffer 
\newline 
;; p\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-print-c-sexp\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB print command for data at 
\newline 
;;\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 buffer point 
\newline 
;; g\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-goto-sdcdb\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Goto the SDCDB output buffer 
\newline 
;; t\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-mode\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Toggles Sdcdbsrc mode (turns it off) 
\newline 
;; 
\newline 
;; C-c C-f\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-finish-from-src\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
SDCDB finish command 
\newline 
;; 
\newline 
;; C-x SPC\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdb-break\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Set break for line with point 
\newline 
;; ESC t\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-mode\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
Toggle Sdcdbsrc mode 
\newline 
;; ESC m\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 sdcdbsrc-srcmode\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
\SpecialChar ~
 Toggle list mode 
\newline 
;; 
\family default 

\newline 

\layout Section

Other Processors
\layout Subsection

The Z80 and gbz80 port
\layout Standard

SDCC can target both the Zilog Z80 and the Nintendo Gameboy's Z80-like gbz80.
 The port is incomplete - long support is incomplete (mul, div and mod are
 unimplimented), and both float and bitfield support is missing.
 Apart from that the code generated is correct.
\layout Standard

As always, the code is the authoritave reference - see z80/ralloc.c and z80/gen.c.
 The stack frame is similar to that generated by the IAR Z80 compiler.
 IX is used as the base pointer, HL is used as a temporary register, and
 BC and DE are available for holding varibles.
 IY is currently unusued.
 Return values are stored in HL.
 One bad side effect of using IX as the base pointer is that a functions
 stack frame is limited to 127 bytes - this will be fixed in a later version.
\layout Section

Support
\layout Standard

SDCC has grown to be a large project.
 The compiler alone (without the preprocessor, assembler and linker) is
 about 40,000 lines of code (blank stripped).
 The open source nature of this project is a key to its continued growth
 and support.
 You gain the benefit and support of many active software developers and
 end users.
 Is SDCC perfect? No, that's why we need your help.
 The developers take pride in fixing reported bugs.
 You can help by reporting the bugs and helping other SDCC users.
 There are lots of ways to contribute, and we encourage you to take part
 in making SDCC a great software package.
\layout Subsection

Reporting Bugs
\layout Standard

Send an email to the mailing list at 'user-sdcc@sdcc.sourceforge.net' or 'devel-sd
cc@sdcc.sourceforge.net'.
 Bugs will be fixed ASAP.
 When reporting a bug, it is very useful to include a small test program
 which reproduces the problem.
 If you can isolate the problem by looking at the generated assembly code,
 this can be very helpful.
 Compiling your program with the --dumpall option can sometimes be useful
 in locating optimization problems.
\layout Section

Acknowledgments
\layout Standard

Sandeep Dutta (sandeep.dutta@usa.net) - SDCC, the compiler, MCS51 code generator,
 Debugger, AVR port
\newline 
Alan Baldwin (baldwin@shop-pdp.kent.edu) - Initial version of ASXXXX & ASLINK.
 
\newline 
John Hartman (jhartman@compuserve.com) - Porting ASXXX & ASLINK for 8051
\newline 
Dmitry S.
 Obukhov (dso@usa.net) - malloc & serial i/o routines.
 
\newline 
Daniel Drotos (drdani@mazsola.iit.uni-miskolc.hu) - for his Freeware simulator
\newline 
Malini Dutta(malini_dutta@hotmail.com) - my wife for her patience and support.
\newline 
Unknown - for the GNU C - preprocessor.
\newline 
Michael Hope - The Z80 and Z80GB port, 186 development
\newline 
Kevin Vigor - The DS390 port.
\newline 
Johan Knol - Lots of fixes and enhancements, DS390/TINI libs.
\newline 
Scott Datallo - The PIC port.
\newline 

\newline 

\emph on 
Thanks to all the other volunteer developers who have helped with coding,
 testing, web-page creation, distribution sets, etc.
 You know who you are :-)
\emph default 

\newline 

\layout Standard

This document was initially written by Sandeep Dutta
\layout Standard

All product names mentioned herein may be trademarks of their respective
 companies.
 
\layout Standard


\begin_inset LatexCommand \printindex{}

\end_inset 


\the_end