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| <!--*********************************************************************--> |
| <h1>Hacking on Clang</h1> |
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| |
| <p>This document provides some hints for how to get started hacking |
| on Clang for developers who are new to the Clang and/or LLVM |
| codebases.</p> |
| <ul> |
| <li><a href="#docs">Developer Documentation</a></li> |
| <li><a href="#debugging">Debugging</a></li> |
| <li><a href="#testing">Testing</a></li> |
| <li><a href="#irgen">LLVM IR Generation</a></li> |
| </ul> |
| |
| <!--=====================================================================--> |
| <h2 id="docs">Developer Documentation</h2> |
| <!--=====================================================================--> |
| |
| <p>Both Clang and LLVM use doxygen to provide API documentation. Their |
| respective web pages (generated nightly) are here:</p> |
| <ul> |
| <li><a href="http://clang.llvm.org/doxygen">Clang</a></li> |
| <li><a href="http://llvm.org/doxygen">LLVM</a></li> |
| </ul> |
| |
| <p>For work on the LLVM IR generation, the LLVM assembly language |
| <a href="http://llvm.org/docs/LangRef.html">reference manual</a> is |
| also useful.</p> |
| |
| <!--=====================================================================--> |
| <h2 id="debugging">Debugging</h2> |
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| |
| <p>Inspecting data structures in a debugger:</p> |
| <ul> |
| <li>Many LLVM and Clang data structures provide |
| a <tt>dump()</tt> method which will print a description of the |
| data structure to <tt>stderr</tt>.</li> |
| <li>The <a href="docs/InternalsManual.html#QualType"><tt>QualType</tt></a> |
| structure is used pervasively. This is a simple value class for |
| wrapping types with qualifiers; you can use |
| the <tt>isConstQualified()</tt>, for example, to get one of the |
| qualifiers, and the <tt>getTypePtr()</tt> method to get the |
| wrapped <tt>Type*</tt> which you can then dump.</li> |
| </ul> |
| |
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| <h2 id="testing">Testing</h2> |
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| |
| <p>Clang includes a basic regression suite in the tree which can be |
| run with <tt>make test</tt> from the top-level clang directory, or |
| just <tt>make</tt> in the <em>test</em> sub-directory. <tt>make |
| report</tt> can be used after running the tests to summarize the |
| results, and <tt>make VERBOSE=1</tt> can be used to show more detail |
| about what is being run.</p> |
| |
| <p>The regression suite can also be run with Valgrind by running |
| <tt>make test VG=1</tt> in the top-level clang directory.</p> |
| |
| <p>For more intensive changes, running |
| the <a href="http://llvm.org/docs/TestingGuide.html#testsuiterun">LLVM |
| Test Suite</a> with clang is recommended. Currently the best way to |
| override LLVMGCC, as in: <tt>make LLVMGCC="ccc -std=gnu89" |
| TEST=nightly report</tt> (make sure ccc is in your PATH or use the |
| full path).</p> |
| |
| <!--=====================================================================--> |
| <h2 id="irgen">LLVM IR Generation</h2> |
| <!--=====================================================================--> |
| |
| <p>The LLVM IR generation part of clang handles conversion of the |
| AST nodes output by the Sema module to the LLVM Intermediate |
| Representation (IR). Historically, this was referred to as |
| "codegen", and the Clang code for this lives |
| in <tt>lib/CodeGen</tt>.</p> |
| |
| <p>The output is most easily inspected using the <tt>-emit-llvm</tt> |
| option to clang (possibly in conjunction with <tt>-o -</tt>). You |
| can also use <tt>-emit-llvm-bc</tt> to write an LLVM bitcode file |
| which can be processed by the suite of LLVM tools |
| like <tt>llvm-dis</tt>, <tt>llvm-nm</tt>, etc. See the LLVM |
| <a href="http://llvm.org/docs/CommandGuide/">Command Guide</a> |
| for more information.</p> |
| |
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