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11<div class="document" id="tutorial-using-llvmc">
12<h1 class="title">Tutorial - Using LLVMC</h1>
13
14<!-- This file was automatically generated by rst2html.
15Please do not edit directly!
16The ReST source lives in the directory 'tools/llvmc/doc'. -->
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
30as the <tt class="docutils literal"><span class="pre">gcc</span></tt> program does for GCC - the difference being that LLVMC
31is designed to be more adaptable and easier to customize. Most of
32LLVMC functionality is implemented via plugins, which can be loaded
33dynamically or compiled in. This tutorial describes the basic usage
34and 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
39much as possible, so most of the familiar options work:</p>
40<pre class="literal-block">
41$ llvmc -O3 -Wall hello.cpp
42$ ./a.out
43hello
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
46commands are executed by using the <tt class="docutils literal"><span class="pre">-v</span></tt> option). For further help on
47command-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
52be 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
67Hello
68</pre>
69<p>Here we link our plugin with the LLVMC core statically to form an executable
70file called <tt class="docutils literal"><span class="pre">mygcc</span></tt>. It is also possible to build our plugin as a dynamic
71library to be loaded by the <tt class="docutils literal"><span class="pre">llvmc</span></tt> executable (or any other LLVMC-based
72standalone 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
76include &quot;llvm/CompilerDriver/Common.td&quot;
77
78// Tool descriptions
79def 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
88def LanguageMap : LanguageMap&lt;[LangToSuffixes&lt;&quot;c&quot;, [&quot;c&quot;]&gt;]&gt;;
89
90// Compilation graph
91def 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,
94language map, and the compilation graph definition.</p>
95<p>At the heart of LLVMC is the idea of a compilation graph: vertices in
96this graph are tools, and edges represent a transformation path
97between two tools (for example, assembly source produced by the
98compiler can be transformed into executable code by an assembler). The
99compilation 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
102in the example above should be self-explanatory; the <tt class="docutils literal"><span class="pre">sink</span></tt> property
103means that all options lacking an explicit description should be
104forwarded 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
106and is used for deciding which toolchain corresponds to a given input
107file.</p>
108<p>To learn more about LLVMC customization, refer to the reference
109manual 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
122Last modified: $Date: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $
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