docs/CompilerDriverTutorial.html

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  11 <div class="document" id="tutorial-using-llvmc">
  12 <h1 class="title">Tutorial - Using LLVMC</h1>
  13
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  17 <div class="contents topic" id="contents">
  18 <p class="topic-title first">Contents</p>
  19 <ul class="simple">
  20 <li><a class="reference internal" href="#introduction" id="id1">Introduction</a></li>
  21 <li><a class="reference internal" href="#compiling-with-llvmc" id="id2">Compiling with LLVMC</a></li>
  22 <li><a class="reference internal" href="#using-llvmc-to-generate-toolchain-drivers" id="id3">Using LLVMC to generate toolchain drivers</a></li>
  23 </ul>
  24 </div>
  25 <div class="doc_author">
  26 <p>Written by <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a></p>
  27 </div><div class="section" id="introduction">
  28 <h1><a class="toc-backref" href="#id1">Introduction</a></h1>
  29 <p>LLVMC is a generic compiler driver, which plays the same role for LLVM
  30 as the <tt class="docutils literal"><span class="pre">gcc</span></tt> program does for GCC - the difference being that LLVMC
  31 is designed to be more adaptable and easier to customize. Most of
  32 LLVMC functionality is implemented via plugins, which can be loaded
  33 dynamically or compiled in. This tutorial describes the basic usage
  34 and configuration of LLVMC.</p>
  35 </div>
  36 <div class="section" id="compiling-with-llvmc">
  37 <h1><a class="toc-backref" href="#id2">Compiling with LLVMC</a></h1>
  38 <p>In general, LLVMC tries to be command-line compatible with <tt class="docutils literal"><span class="pre">gcc</span></tt> as
  39 much as possible, so most of the familiar options work:</p>
  40 <pre class="literal-block">
  41 $ llvmc -O3 -Wall hello.cpp
  42 $ ./a.out
  43 hello
  44 </pre>
  45 <p>This will invoke <tt class="docutils literal"><span class="pre">llvm-g++</span></tt> under the hood (you can see which
  46 commands are executed by using the <tt class="docutils literal"><span class="pre">-v</span></tt> option). For further help on
  47 command-line LLVMC usage, refer to the <tt class="docutils literal"><span class="pre">llvmc</span> <span class="pre">--help</span></tt> output.</p>
  48 </div>
  49 <div class="section" id="using-llvmc-to-generate-toolchain-drivers">
  50 <h1><a class="toc-backref" href="#id3">Using LLVMC to generate toolchain drivers</a></h1>
  51 <p>LLVMC plugins are written mostly using <a class="reference external" href="http://llvm.org/docs/TableGenFundamentals.html">TableGen</a>, so you need to
  52 be familiar with it to get anything done.</p>
  53 <p>Start by compiling <tt class="docutils literal"><span class="pre">example/Simple</span></tt>, which is a primitive wrapper for
  54 <tt class="docutils literal"><span class="pre">gcc</span></tt>:</p>
  55 <pre class="literal-block">
  56 $ cd $LLVM_DIR/tools/llvmc
  57 $ cp -r example/Simple plugins/Simple
  58
  59   # NB: A less verbose way to compile standalone LLVMC-based drivers is
  60   # described in the reference manual.
  61
  62 $ make LLVMC_BASED_DRIVER_NAME=mygcc LLVMC_BUILTIN_PLUGINS=Simple
  63 $ cat &gt; hello.c
  64 [...]
  65 $ mygcc hello.c
  66 $ ./hello.out
  67 Hello
  68 </pre>
  69 <p>Here we link our plugin with the LLVMC core statically to form an executable
  70 file called <tt class="docutils literal"><span class="pre">mygcc</span></tt>. It is also possible to build our plugin as a dynamic
  71 library to be loaded by the <tt class="docutils literal"><span class="pre">llvmc</span></tt> executable (or any other LLVMC-based
  72 standalone driver); this is described in the reference manual.</p>
  73 <p>Contents of the file <tt class="docutils literal"><span class="pre">Simple.td</span></tt> look like this:</p>
  74 <pre class="literal-block">
  75 // Include common definitions
  76 include &quot;llvm/CompilerDriver/Common.td&quot;
  77
  78 // Tool descriptions
  79 def gcc : Tool&lt;
  80 [(in_language &quot;c&quot;),
  81  (out_language &quot;executable&quot;),
  82  (output_suffix &quot;out&quot;),
  83  (cmd_line &quot;gcc $INFILE -o $OUTFILE&quot;),
  84  (sink)
  85 ]&gt;;
  86
  87 // Language map
  88 def LanguageMap : LanguageMap&lt;[LangToSuffixes&lt;&quot;c&quot;, [&quot;c&quot;]&gt;]&gt;;
  89
  90 // Compilation graph
  91 def CompilationGraph : CompilationGraph&lt;[Edge&lt;&quot;root&quot;, &quot;gcc&quot;&gt;]&gt;;
  92 </pre>
  93 <p>As you can see, this file consists of three parts: tool descriptions,
  94 language map, and the compilation graph definition.</p>
  95 <p>At the heart of LLVMC is the idea of a compilation graph: vertices in
  96 this graph are tools, and edges represent a transformation path
  97 between two tools (for example, assembly source produced by the
  98 compiler can be transformed into executable code by an assembler). The
  99 compilation graph is basically a list of edges; a special node named
 100 <tt class="docutils literal"><span class="pre">root</span></tt> is used to mark graph entry points.</p>
 101 <p>Tool descriptions are represented as property lists: most properties
 102 in the example above should be self-explanatory; the <tt class="docutils literal"><span class="pre">sink</span></tt> property
 103 means that all options lacking an explicit description should be
 104 forwarded to this tool.</p>
 105 <p>The <tt class="docutils literal"><span class="pre">LanguageMap</span></tt> associates a language name with a list of suffixes
 106 and is used for deciding which toolchain corresponds to a given input
 107 file.</p>
 108 <p>To learn more about LLVMC customization, refer to the reference
 109 manual and plugin source code in the <tt class="docutils literal"><span class="pre">plugins</span></tt> directory.</p>
 110 <hr />
 111 <address>
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 119 <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a><br />
 120 <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br />
 121
 122 Last modified: $Date: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $
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