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<h1>6502bench SourceGen: Code Generation &amp; Assembly</h1>
<p><a href="index.html">Back to index</a></p>
<p>SourceGen can generate an assembly source file that, when fed into
the target assembler, will recreate the original data file exactly.
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Every assembler is different, so support must be added to SourceGen
for each.</p>
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<p>The generation / assembly dialog can be opened with File &gt; Assemble.</p>
<h2><a name="supported">Supported Assemblers</a></h2>
<p>SourceGen currently supports the following cross-assemblers:</p>
<ul>
<li><a href="https://cc65.github.io/">cc65</a> v2.17 or later</li>
<li><a href="https://www.brutaldeluxe.fr/products/crossdevtools/merlin/">Merlin 32</a> v1.0.0 or later</li>
</ul>
<h3><a name="version">Version-Specific Code Generation</a></h3>
<p>Code generation must be tailored to the specific version of the
assembler. This is most easily understood with an example.</p>
<p>If you write <code>MVN $01,$02</code>, the assembler is expected to output
<code>54 02 01</code>, with the arguments reversed. cc65 v2.17 doesn't
do that; this is a bug that was fixed in a later version. So if you're
generating code for v2.17, you want to create source code with the
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arguments the wrong way around.</p>
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<p>Having version-dependent source code is a bad idea, so SourceGen
just outputs raw hex bytes for MVN/MVP instructions. This yields the
correct code for all versions of the assembler, but is ugly and
annoying. So we want to output actual MVN/MVP instructions when producing
code for newer versions of the assembler.</p>
<p>When you configure a cross-assembler, SourceGen executes it and
extracts the version information from the command-line output stream.
This is used by the generator to ensure that the output will compile.
If no assembler is configured, SourceGen will produce code optimized
for the latest version of the assembler.</p>
<h2><a name="generate">Generating Source Code</a></h2>
<p>Cross assemblers tend to generate additional files, either compiler
intermediaries ("file.o") or metadata ("_FileInformation.txt"). Some
generators may produce multiple source files, perhaps a link script or
symbol definition header to go with the assembly source. To avoid
spreading files across the filesystem, SourceGen does all of its work
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in the same directory where the project lives. Before you can generate
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code, you have to have given your project a name by saving it.</p>
<p>The Generate and Assemble dialog has a drop-down list near the top
that lets you pick which assembler to target. The name of the assembler
will be shown with the detected version number. If the assembler
executable isn't configured, "[latest version]" will be shown instead
of a version number.</p>
<p>The Settings button will take you directly to the assembler configuration
tab in the application settings dialog.
<p>Hit the Generate button to generate the source code into a file on disk.
The file will use the project name, with the ".dis65" replaced by
"_&lt;assembler&gt;.S".</p>
<p>The first 64KiB of each generated file will be shown in the preview
window. If multiple files were generated, you can use the "preview file"
drop-down to select between them. Line numbers are
prepended to each line to make it easier to track down errors.</p>
<h3><a name="localizer">Label Localizer</a></h3>
<p>The label localizer is an optional feature that automatically converts
some labels to an assembler-specific less-than-global label format. Local
labels may be reusable (e.g. using "]LOOP" for multiple consecutive
loops is easier to understand than giving each one a unique label) or
reduce the size of a generated link table. There are usually restrictions
on local labels, e.g. references to them may not be allowed to cross a
global label definition, which the localizer factors in automatically.</p>
<p>The localizer is somewhat experimental at this time, and can be
disabled from the
<a href="settings.html#app-settings">application settings</a>.</p>
<h2><a name="assemble">Cross-Assembling Generated Code</a></h2>
<p>After generating sources, if you have a cross-assembler executable
configured, you can run it by clicking the "Run Assembler" button. The
command-line output will be displayed, with stdout and stderr separated.
(I'd prefer them to be interleaved, but that's not what the system
provides.)</p>
<p>The output will show the assembler's exit code, which will be zero
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on success (note: sometimes they lie.) If it appeared to succeed,
SourceGen will then compare the assembler's output to the original file,
and report any differences.</p>
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<p>Failures here may be due to bugs in the cross-assembler or in
SourceGen. However, SourceGen can generally work around assembler bugs,
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so any failure is an opportunity for improvement.</p>
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