-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
-<html>
+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
- <title>The LLVM Compiler Driver (llvmc)</title>
- <link rel="stylesheet" href="llvm.css" type="text/css">
- <style type="text/css">
- TR, TD { border: 2px solid gray; padding: 4pt 4pt 2pt 2pt; }
- TH { border: 2px solid gray; font-weight: bold; font-size: 105%; }
- TABLE { text-align: center; border: 2px solid black;
- border-collapse: collapse; margin-top: 1em; margin-left: 1em;
- margin-right: 1em; margin-bottom: 1em; }
- .td_left { border: 2px solid gray; text-align: left; }
- </style>
- <meta name="author" content="Reid Spencer" name="author">
- <meta name="description"
- content="A description of the use and design of the LLVM Compiler Driver.">
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<meta name="generator" content="Docutils 0.6: http://docutils.sourceforge.net/" />
+<title>Customizing LLVMC: Reference Manual</title>
+<link rel="stylesheet" href="llvm.css" type="text/css" />
</head>
<body>
-<div class="doc_title">The LLVM Compiler Driver (llvmc)</div>
-<p class="doc_warning">NOTE: This document is a work in progress!</p>
-<ol>
- <li><a href="#abstract">Abstract</a></li>
- <li><a href="#introduction">Introduction</a>
- <ol>
- <li><a href="#purpose">Purpose</a></li>
- <li><a href="#operation">Operation</a></li>
- <li><a href="#phases">Phases</a></li>
- <li><a href="#actions">Actions</a></li>
- </ol>
- </li>
- <li><a href="#details">Details</a>
- <li><a href="#configuration">Configuration</a>
- <li><a href="#glossary">Glossary</a>
-</ol>
+<div class="document" id="customizing-llvmc-reference-manual">
+<h1 class="title">Customizing LLVMC: Reference Manual</h1>
+
+<!-- This file was automatically generated by rst2html.
+Please do not edit directly!
+The ReST source lives in the directory 'tools/llvmc/doc'. -->
+<div class="contents topic" id="contents">
+<p class="topic-title first">Contents</p>
+<ul class="simple">
+<li><a class="reference internal" href="#introduction" id="id7">Introduction</a></li>
+<li><a class="reference internal" href="#compiling-with-llvmc" id="id8">Compiling with <tt class="docutils literal">llvmc</tt></a></li>
+<li><a class="reference internal" href="#predefined-options" id="id9">Predefined options</a></li>
+<li><a class="reference internal" href="#compiling-llvmc-based-drivers" id="id10">Compiling LLVMC-based drivers</a></li>
+<li><a class="reference internal" href="#customizing-llvmc-the-compilation-graph" id="id11">Customizing LLVMC: the compilation graph</a></li>
+<li><a class="reference internal" href="#describing-options" id="id12">Describing options</a></li>
+<li><a class="reference internal" href="#conditional-evaluation" id="id13">Conditional evaluation</a></li>
+<li><a class="reference internal" href="#writing-a-tool-description" id="id14">Writing a tool description</a><ul>
+<li><a class="reference internal" href="#id4" id="id15">Actions</a></li>
+</ul>
+</li>
+<li><a class="reference internal" href="#language-map" id="id16">Language map</a></li>
+<li><a class="reference internal" href="#option-preprocessor" id="id17">Option preprocessor</a></li>
+<li><a class="reference internal" href="#more-advanced-topics" id="id18">More advanced topics</a><ul>
+<li><a class="reference internal" href="#hooks-and-environment-variables" id="id19">Hooks and environment variables</a></li>
+<li><a class="reference internal" href="#debugging" id="id20">Debugging</a></li>
+<li><a class="reference internal" href="#conditioning-on-the-executable-name" id="id21">Conditioning on the executable name</a></li>
+</ul>
+</li>
+</ul>
+</div>
<div class="doc_author">
-<p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
-</p>
+<p>Written by <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a></p>
+</div><div class="section" id="introduction">
+<h1><a class="toc-backref" href="#id7">Introduction</a></h1>
+<p>LLVMC is a generic compiler driver, designed to be customizable and
+extensible. It plays the same role for LLVM as the <tt class="docutils literal">gcc</tt> program does for
+GCC - LLVMC's job is essentially to transform a set of input files into a set of
+targets depending on configuration rules and user options. What makes LLVMC
+different is that these transformation rules are completely customizable - in
+fact, LLVMC knows nothing about the specifics of transformation (even the
+command-line options are mostly not hard-coded) and regards the transformation
+structure as an abstract graph. The structure of this graph is described in
+high-level TableGen code, from which an efficient C++ representation is
+automatically derived. This makes it possible to adapt LLVMC for other
+purposes - for example, as a build tool for game resources.</p>
+<p>Because LLVMC employs <a class="reference external" href="http://llvm.org/docs/TableGenFundamentals.html">TableGen</a> as its configuration language, you
+need to be familiar with it to customize LLVMC.</p>
</div>
-
-<!-- *********************************************************************** -->
-<div class="doc_section"> <a name="abstract">Abstract</a></div>
-<!-- *********************************************************************** -->
-<div class="doc_text">
- <p>This document describes the requirements, design, and configuration of the
- LLVM compiler driver, <tt>llvmc</tt>. The compiler driver knows about LLVM's
- tool set and can be configured to know about a variety of compilers for
- source languages. It uses this knowledge to execute the tools necessary
- to accomplish general compilation, optimization, and linking tasks. The main
- purpose of <tt>llvmc</tt> is to provide a simple and consistent interface to
- all compilation tasks. This reduces the burden on the end user who can just
- learn to use <tt>llvmc</tt> instead of the entire LLVM tool set and all the
- source language compilers compatible with LLVM.</p>
+<div class="section" id="compiling-with-llvmc">
+<h1><a class="toc-backref" href="#id8">Compiling with <tt class="docutils literal">llvmc</tt></a></h1>
+<p>LLVMC tries hard to be as compatible with <tt class="docutils literal">gcc</tt> as possible,
+although there are some small differences. Most of the time, however,
+you shouldn't be able to notice them:</p>
+<pre class="literal-block">
+$ # This works as expected:
+$ llvmc -O3 -Wall hello.cpp
+$ ./a.out
+hello
+</pre>
+<p>One nice feature of LLVMC is that one doesn't have to distinguish between
+different compilers for different languages (think <tt class="docutils literal">g++</tt> vs. <tt class="docutils literal">gcc</tt>) - the
+right toolchain is chosen automatically based on input language names (which
+are, in turn, determined from file extensions). If you want to force files
+ending with ".c" to compile as C++, use the <tt class="docutils literal"><span class="pre">-x</span></tt> option, just like you would
+do it with <tt class="docutils literal">gcc</tt>:</p>
+<pre class="literal-block">
+$ # hello.c is really a C++ file
+$ llvmc -x c++ hello.c
+$ ./a.out
+hello
+</pre>
+<p>On the other hand, when using LLVMC as a linker to combine several C++
+object files you should provide the <tt class="docutils literal"><span class="pre">--linker</span></tt> option since it's
+impossible for LLVMC to choose the right linker in that case:</p>
+<pre class="literal-block">
+$ llvmc -c hello.cpp
+$ llvmc hello.o
+[A lot of link-time errors skipped]
+$ llvmc --linker=c++ hello.o
+$ ./a.out
+hello
+</pre>
+<p>By default, LLVMC uses <tt class="docutils literal"><span class="pre">llvm-gcc</span></tt> to compile the source code. It is also
+possible to choose the <tt class="docutils literal">clang</tt> compiler with the <tt class="docutils literal"><span class="pre">-clang</span></tt> option.</p>
</div>
-<!-- *********************************************************************** -->
-<div class="doc_section"> <a name="introduction">Introduction</a></div>
-<!-- *********************************************************************** -->
-<div class="doc_text">
- <p>The <tt>llvmc</tt> <a href="def_tool">tool</a> is a configurable compiler
- <a href="def_driver">driver</a>. As such, it isn't the compiler, optimizer,
- or linker itself but it drives (invokes) other software that perform those
- tasks. If you are familiar with the GNU Compiler Collection's <tt>gcc</tt>
- tool, <tt>llvmc</tt> is very similar.</p>
- <p>The following introductory sections will help you understand why this tool
- is necessary and what it does.</p>
+<div class="section" id="predefined-options">
+<h1><a class="toc-backref" href="#id9">Predefined options</a></h1>
+<p>LLVMC has some built-in options that can't be overridden in the TableGen code:</p>
+<ul class="simple">
+<li><tt class="docutils literal"><span class="pre">-o</span> FILE</tt> - Output file name.</li>
+<li><tt class="docutils literal"><span class="pre">-x</span> LANGUAGE</tt> - Specify the language of the following input files
+until the next -x option.</li>
+<li><tt class="docutils literal"><span class="pre">-v</span></tt> - Enable verbose mode, i.e. print out all executed commands.</li>
+<li><tt class="docutils literal"><span class="pre">--save-temps</span></tt> - Write temporary files to the current directory and do not
+delete them on exit. This option can also take an argument: the
+<tt class="docutils literal"><span class="pre">--save-temps=obj</span></tt> switch will write files into the directory specified with
+the <tt class="docutils literal"><span class="pre">-o</span></tt> option. The <tt class="docutils literal"><span class="pre">--save-temps=cwd</span></tt> and <tt class="docutils literal"><span class="pre">--save-temps</span></tt> switches are
+both synonyms for the default behaviour.</li>
+<li><tt class="docutils literal"><span class="pre">--temp-dir</span> DIRECTORY</tt> - Store temporary files in the given directory. This
+directory is deleted on exit unless <tt class="docutils literal"><span class="pre">--save-temps</span></tt> is specified. If
+<tt class="docutils literal"><span class="pre">--save-temps=obj</span></tt> is also specified, <tt class="docutils literal"><span class="pre">--temp-dir</span></tt> is given the
+precedence.</li>
+<li><tt class="docutils literal"><span class="pre">--check-graph</span></tt> - Check the compilation for common errors like mismatched
+output/input language names, multiple default edges and cycles. Exit with code
+zero if no errors were found, and return the number of found errors
+otherwise. Hidden option, useful for debugging.</li>
+<li><tt class="docutils literal"><span class="pre">--view-graph</span></tt> - Show a graphical representation of the compilation graph
+and exit. Requires that you have <tt class="docutils literal">dot</tt> and <tt class="docutils literal">gv</tt> programs installed. Hidden
+option, useful for debugging.</li>
+<li><tt class="docutils literal"><span class="pre">--write-graph</span></tt> - Write a <tt class="docutils literal"><span class="pre">compilation-graph.dot</span></tt> file in the current
+directory with the compilation graph description in Graphviz format (identical
+to the file used by the <tt class="docutils literal"><span class="pre">--view-graph</span></tt> option). The <tt class="docutils literal"><span class="pre">-o</span></tt> option can be
+used to set the output file name. Hidden option, useful for debugging.</li>
+<li><tt class="docutils literal"><span class="pre">--help</span></tt>, <tt class="docutils literal"><span class="pre">--help-hidden</span></tt>, <tt class="docutils literal"><span class="pre">--version</span></tt> - These options have
+their standard meaning.</li>
+</ul>
</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="purpose">Purpose</a></div>
-<div class="doc_text">
- <p><tt>llvmc</tt> was invented to make compilation with LLVM based compilers
- easier. To accomplish this, <tt>llvmc</tt> strives to:</p>
- <ul>
- <li>Be the single point of access to most of the LLVM tool set.</li>
- <li>Hide the complexities of the LLVM tools through a single interface.</li>
- <li>Provide a consistent interface for compiling all languages.</li>
- </ul>
- <p>Additionally, <tt>llvmc</tt> makes it easier to write a compiler for use
- with LLVM, because it:</p>
- <ul>
- <li>Makes integration of existing non-LLVM tools simple.</li>
- <li>Extends the capabilities of minimal front ends by optimizing their
- output.</li>
- <li>Reduces the number of interfaces a compiler writer must know about
- before a working compiler can be completed (essentially only the VMCore
- interfaces need to be understood).</li>
- <li>Supports source language translator invocation via both dynamically
- loadable shared objects and invocation of an executable.</li>
- </ol>
-</p>
+<div class="section" id="compiling-llvmc-based-drivers">
+<h1><a class="toc-backref" href="#id10">Compiling LLVMC-based drivers</a></h1>
+<p>It's easiest to start working on your own LLVMC driver by copying the skeleton
+project which lives under <tt class="docutils literal">$LLVMC_DIR/examples/Skeleton</tt>:</p>
+<pre class="literal-block">
+$ cd $LLVMC_DIR/examples
+$ cp -r Skeleton MyDriver
+$ cd MyDriver
+$ ls
+AutoGenerated.td Hooks.cpp Main.cpp Makefile
+</pre>
+<p>As you can see, our basic driver consists of only three files (not counting the
+build script). <tt class="docutils literal">AutoGenerated.td</tt> contains TableGen description of the
+compilation graph; its format is documented in the following
+sections. <tt class="docutils literal">Hooks.cpp</tt> is an empty file that should be used for hook
+definitions (see <a class="reference internal" href="#hooks">below</a>). <tt class="docutils literal">Main.cpp</tt> is just a helper used to compile the
+auto-generated C++ code produced from TableGen source.</p>
+<p>The first thing that you should do is to change the <tt class="docutils literal">LLVMC_BASED_DRIVER</tt>
+variable in the <tt class="docutils literal">Makefile</tt>:</p>
+<pre class="literal-block">
+LLVMC_BASED_DRIVER=MyDriver
+</pre>
+<p>It can also be a good idea to put your TableGen code into a file with a less
+generic name:</p>
+<pre class="literal-block">
+$ touch MyDriver.td
+$ vim AutoGenerated.td
+[...]
+include "MyDriver.td"
+</pre>
+<p>If you have more than one TableGen source file, they all should be included from
+<tt class="docutils literal">AutoGenerated.td</tt>, since this file is used by the build system to generate
+C++ code.</p>
+<p>To build your driver, just <tt class="docutils literal">cd</tt> to its source directory and run <tt class="docutils literal">make</tt>. The
+resulting executable will be put into <tt class="docutils literal"><span class="pre">$LLVM_OBJ_DIR/$(BuildMode)/bin</span></tt>.</p>
+<p>If you're compiling LLVM with different source and object directories, then you
+must perform the following additional steps before running <tt class="docutils literal">make</tt>:</p>
+<pre class="literal-block">
+# LLVMC_SRC_DIR = $LLVM_SRC_DIR/tools/llvmc/
+# LLVMC_OBJ_DIR = $LLVM_OBJ_DIR/tools/llvmc/
+$ mkdir $LLVMC_OBJ_DIR/examples/MyDriver/
+$ cp $LLVMC_SRC_DIR/examples/MyDriver/Makefile \
+ $LLVMC_OBJ_DIR/examples/MyDriver/
+$ cd $LLVMC_OBJ_DIR/examples/MyDriver
+$ make
+</pre>
</div>
+<div class="section" id="customizing-llvmc-the-compilation-graph">
+<h1><a class="toc-backref" href="#id11">Customizing LLVMC: the compilation graph</a></h1>
+<p>Each TableGen configuration file should include the common definitions:</p>
+<pre class="literal-block">
+include "llvm/CompilerDriver/Common.td"
+</pre>
+<p>Internally, LLVMC stores information about possible source transformations in
+form of a graph. Nodes in this graph represent tools, and edges between two
+nodes represent a transformation path. A special "root" node is used to mark
+entry points for the transformations. LLVMC also assigns a weight to each edge
+(more on this later) to choose between several alternative edges.</p>
+<p>The definition of the compilation graph (see file <tt class="docutils literal">llvmc/src/Base.td</tt> for an
+example) is just a list of edges:</p>
+<pre class="literal-block">
+def CompilationGraph : CompilationGraph<[
+ Edge<"root", "llvm_gcc_c">,
+ Edge<"root", "llvm_gcc_assembler">,
+ ...
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="operation">Operation</a></div>
-<div class="doc_text">
- <p>At a high level, <tt>llvmc</tt> operation is very simple. The basic action
- taken by <tt>llvmc</tt> is to simply invoke some tool or set of tools to fill
- the user's request for compilation. Every execution of <tt>llvmc</tt>takes the
- following sequence of steps:<br/>
- <dl>
- <dt><b>Collect Command Line Options</b></dt>
- <dd>The command line options provide the marching orders to <tt>llvmc</tt>
- on what actions it should perform. This is the request the user is making
- of <tt>llvmc</tt> and it is interpreted first. See the <tt>llvmc</tt>
- <a href="CommandGuide/html/llvmc.html">manual page</a> for details on the
- options.</dd>
- <dt><b>Read Configuration Files</b></dt>
- <dd>Based on the options and the suffixes of the filenames presented, a set
- of configuration files are read to configure the actions <tt>llvmc</tt> will
- take. Configuration files are provided by either LLVM or the front end
- compiler tools that B<llvmc> invokes. These files determine what actions
- <tt>llvmc</tt> will take in response to the user's request. See the section
- on <a href="#configuration">configuration</a> for more details.</dd>
- <dt><b>Determine Phases To Execute</b></dt>
- <dd>Based on the command line options and configuration files,
- <tt>llvmc</tt> determines the compilation <a href="#phases">phases</a> that
- must be executed by the user's request. This is the primary work of
- <tt>llvmc</tt>.</dd>
- <dt><b>Determine Actions To Execute</b></dt>
- <dd>Each <a href="#phases">phase</a> to be executed can result in the
- invocation of one or more <a href="#actions">actions</a>. An action is
- either a whole program or a function in a dynamically linked shared library.
- In this step, <tt>llvmc</tt> determines the sequence of actions that must be
- executed. Actions will always be executed in a deterministic order.</dd>
- <dt><b>Execute Actions</b></dt>
- <dd>The <a href="#actions">actions</a> necessary to support the user's
- original request are executed sequentially and deterministically. All
- actions result in either the invocation of a whole program to perform the
- action or the loading of a dynamically linkable shared library and invocation
- of a standard interface function within that library.</dd>
- <dt><b>Termination</b></dt>
- <dd>If any action fails (returns a non-zero result code), <tt>llvmc</tt>
- also fails and returns the result code from the failing action. If
- everything succeeds, <tt>llvmc</tt> will return a zero result code.</dd>
- </dl></p>
- <p><tt>llvmc</tt>'s operation must be simple, regular and predictable.
- Developers need to be able to rely on it to take a consistent approach to
- compilation. For example, the invocation:</p>
- <tt><pre>
- llvmc -O2 x.c y.c z.c -o xyz</pre></tt>
- <p>must produce <i>exactly</i> the same results as:</p>
- <tt><pre>
- llvmc -O2 x.c
- llvmc -O2 y.c
- llvmc -O2 z.c
- llvmc -O2 x.o y.o z.o -o xyz</pre></tt>
- <p>To accomplish this, <tt>llvmc</tt> uses a very simple goal oriented
- procedure to do its work. The overall goal is to produce a functioning
- executable. To accomplish this, <tt>llvmc</tt> always attempts to execute a
- series of compilation <a href="#def_phase">phases</a> in the same sequence.
- However, the user's options to <tt>llvmc</tt> can cause the sequence of phases
- to start in the middle or finish early.</p>
-</div>
+ Edge<"llvm_gcc_c", "llc">,
+ Edge<"llvm_gcc_cpp", "llc">,
+ ...
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="phases"></a>Phases </div>
-<div class="doc_text">
- <p><tt>llvmc</tt> breaks every compilation task into the following five
- distinct phases:</p>
- <dl><dt><b>Preprocessing</b></dt><dd>Not all languages support preprocessing;
- but for those that do, this phase can be invoked. This phase is for
- languages that provide combining, filtering, or otherwise altering with the
- source language input before the translator parses it. Although C and C++
- are the most common users of this phase, other languages may provide their
- own preprocessor (whether its the C pre-processor or not).</dd>
- </dl>
- <dl><dt><b>Translation</b></dt><dd>The translation phase converts the source
- language input into something that LLVM can interpret and use for
- downstream phases. The translation is essentially from "non-LLVM form" to
- "LLVM form".</dd>
- </dl>
- <dl><dt><b>Optimization</b></dt><dd>Once an LLVM Module has been obtained from
- the translation phase, the program enters the optimization phase. This phase
- attempts to optimize all of the input provided on the command line according
- to the options provided.</dd>
- </dl>
- <dl><dt><b>Linking</b></dt><dd>The inputs are combined to form a complete
- program.</dd>
- </dl>
- <p>The following table shows the inputs, outputs, and command line options
- applicabe to each phase.</p>
- <table>
- <tr>
- <th style="width: 10%">Phase</th>
- <th style="width: 25%">Inputs</th>
- <th style="width: 25%">Outputs</th>
- <th style="width: 40%">Options</th>
- </tr>
- <tr><td><b>Preprocessing</b></td>
- <td class="td_left"><ul><li>Source Language File</li></ul></td>
- <td class="td_left"><ul><li>Source Language File</li></ul></td>
- <td class="td_left"><dl>
- <dt><tt>-E</tt></dt>
- <dd>Stops the compilation after preprocessing</dd>
- </dl></td>
- </tr>
- <tr>
- <td><b>Translation</b></td>
- <td class="td_left"><ul>
- <li>Source Language File</li>
- </ul></td>
- <td class="td_left"><ul>
- <li>LLVM Assembly</li>
- <li>LLVM Bytecode</li>
- <li>LLVM C++ IR</li>
- </ul></td>
- <td class="td_left"><dl>
- <dt><tt>-c</tt></dt>
- <dd>Stops the compilation after translation so that optimization and
- linking are not done.</dd>
- <dt><tt>-S</tt></dt>
- <dd>Stops the compilation before object code is written so that only
- assembly code remains.</dd>
- </dl></td>
- </tr>
- <tr>
- <td><b>Optimization</b></td>
- <td class="td_left"><ul>
- <li>LLVM Assembly</li>
- <li>LLVM Bytecode</li>
- </ul></td>
- <td class="td_left"><ul>
- <li>LLVM Bytecode</li>
- </ul></td>
- <td class="td_left"><dl>
- <dt><tt>-Ox</tt>
- <dd>This group of options affects the amount of optimization
- performed.</dd>
- </dl></td>
- </tr>
- <tr>
- <td><b>Linking</b></td>
- <td class="td_left"><ul>
- <li>LLVM Bytecode</li>
- <li>Native Object Code</li>
- <li>LLVM Library</li>
- <li>Native Library</li>
- </ul></td>
- <td class="td_left"><ul>
- <li>LLVM Bytecode Executable</li>
- <li>Native Executable</li>
- </ul></td>
- <td class="td_left"><dl>
- <dt><tt>-L</tt></dt><dd>Specifies a path for library search.</dd>
- <dt><tt>-l</tt></dt><dd>Specifies a library to link in.</dd>
- </dl></td>
- </tr>
- </table>
-</div>
+ OptionalEdge<"llvm_gcc_c", "opt", (case (switch_on "opt"),
+ (inc_weight))>,
+ OptionalEdge<"llvm_gcc_cpp", "opt", (case (switch_on "opt"),
+ (inc_weight))>,
+ ...
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="actions"></a>Actions</div>
-<div class="doc_text">
- <p>An action, with regard to <tt>llvmc</tt> is a basic operation that it takes
- in order to fulfill the user's request. Each phase of compilation will invoke
- zero or more actions in order to accomplish that phase.</p>
- <p>Actions come in two forms:<ol>
- <li>Invokable Executables</li>
- <li>Functions in a shared library</li>
- </ul></p>
-</div>
+ OptionalEdge<"llvm_gcc_assembler", "llvm_gcc_cpp_linker",
+ (case (input_languages_contain "c++"), (inc_weight),
+ (or (parameter_equals "linker", "g++"),
+ (parameter_equals "linker", "c++")), (inc_weight))>,
+ ...
-<!-- *********************************************************************** -->
-<div class="doc_section"><a name="details">Details</a></div>
-<!-- *********************************************************************** -->
-<div class="doc_text">
+ ]>;
+</pre>
+<p>As you can see, the edges can be either default or optional, where optional
+edges are differentiated by an additional <tt class="docutils literal">case</tt> expression used to calculate
+the weight of this edge. Notice also that we refer to tools via their names (as
+strings). This makes it possible to add edges to an existing compilation graph
+without having to know about all tool definitions used in the graph.</p>
+<p>The default edges are assigned a weight of 1, and optional edges get a weight of
+0 + 2*N where N is the number of tests that evaluated to true in the <tt class="docutils literal">case</tt>
+expression. It is also possible to provide an integer parameter to
+<tt class="docutils literal">inc_weight</tt> and <tt class="docutils literal">dec_weight</tt> - in this case, the weight is increased (or
+decreased) by the provided value instead of the default 2. Default weight of an
+optional edge can be changed by using the <tt class="docutils literal">default</tt> clause of the <tt class="docutils literal">case</tt>
+construct.</p>
+<p>When passing an input file through the graph, LLVMC picks the edge with the
+maximum weight. To avoid ambiguity, there should be only one default edge
+between two nodes (with the exception of the root node, which gets a special
+treatment - there you are allowed to specify one default edge <em>per language</em>).</p>
+<p>When multiple compilation graphs are defined, they are merged together. Multiple
+edges with the same end nodes are not allowed (i.e. the graph is not a
+multigraph), and will lead to a compile-time error.</p>
+<p>To get a visual representation of the compilation graph (useful for debugging),
+run <tt class="docutils literal">llvmc <span class="pre">--view-graph</span></tt>. You will need <tt class="docutils literal">dot</tt> and <tt class="docutils literal">gsview</tt> installed for
+this to work properly.</p>
</div>
-
-<!-- *********************************************************************** -->
-<div class="doc_section"><a name="configuration">Configuration</a></div>
-<!-- *********************************************************************** -->
-<div class="doc_text">
- <p>This section of the document describes the configuration files used by
- <tt>llvmc</tt>. Configuration information is relatively static for a
- given release of LLVM and a front end compiler. However, the details may
- change from release to release of either. Users are encouraged to simply use
- the various options of the B<llvmc> command and ignore the configuration of
- the tool. These configuration files are for compiler writers and LLVM
- developers. Those wishing to simply use B<llvmc> don't need to understand
- this section but it may be instructive on how the tool works.</p>
+<div class="section" id="describing-options">
+<h1><a class="toc-backref" href="#id12">Describing options</a></h1>
+<p>Command-line options supported by the driver are defined by using an
+<tt class="docutils literal">OptionList</tt>:</p>
+<pre class="literal-block">
+def Options : OptionList<[
+(switch_option "E", (help "Help string")),
+(alias_option "quiet", "q")
+...
+]>;
+</pre>
+<p>As you can see, the option list is just a list of DAGs, where each DAG is an
+option description consisting of the option name and some properties. More than
+one option list can be defined (they are all merged together in the end), which
+can be handy if one wants to separate option groups syntactically.</p>
+<ul>
+<li><p class="first">Possible option types:</p>
+<blockquote>
+<ul class="simple">
+<li><tt class="docutils literal">switch_option</tt> - a simple boolean switch without arguments, for example
+<tt class="docutils literal"><span class="pre">-O2</span></tt> or <tt class="docutils literal"><span class="pre">-time</span></tt>. At most one occurrence is allowed by default.</li>
+<li><tt class="docutils literal">parameter_option</tt> - option that takes one argument, for example
+<tt class="docutils literal"><span class="pre">-std=c99</span></tt>. It is also allowed to use spaces instead of the equality
+sign: <tt class="docutils literal"><span class="pre">-std</span> c99</tt>. At most one occurrence is allowed.</li>
+<li><tt class="docutils literal">parameter_list_option</tt> - same as the above, but more than one option
+occurrence is allowed.</li>
+<li><tt class="docutils literal">prefix_option</tt> - same as the parameter_option, but the option name and
+argument do not have to be separated. Example: <tt class="docutils literal"><span class="pre">-ofile</span></tt>. This can be also
+specified as <tt class="docutils literal"><span class="pre">-o</span> file</tt>; however, <tt class="docutils literal"><span class="pre">-o=file</span></tt> will be parsed incorrectly
+(<tt class="docutils literal">=file</tt> will be interpreted as option value). At most one occurrence is
+allowed.</li>
+<li><tt class="docutils literal">prefix_list_option</tt> - same as the above, but more than one occurrence of
+the option is allowed; example: <tt class="docutils literal"><span class="pre">-lm</span> <span class="pre">-lpthread</span></tt>.</li>
+<li><tt class="docutils literal">alias_option</tt> - a special option type for creating aliases. Unlike other
+option types, aliases are not allowed to have any properties besides the
+aliased option name.
+Usage example: <tt class="docutils literal">(alias_option "preprocess", "E")</tt></li>
+<li><tt class="docutils literal">switch_list_option</tt> - like <tt class="docutils literal">switch_option</tt> with the <tt class="docutils literal">zero_or_more</tt>
+property, but remembers how many times the switch was turned on. Useful
+mostly for forwarding. Example: when <tt class="docutils literal"><span class="pre">-foo</span></tt> is a switch option (with the
+<tt class="docutils literal">zero_or_more</tt> property), the command <tt class="docutils literal">driver <span class="pre">-foo</span> <span class="pre">-foo</span></tt> is forwarded
+as <tt class="docutils literal"><span class="pre">some-tool</span> <span class="pre">-foo</span></tt>, but when <tt class="docutils literal"><span class="pre">-foo</span></tt> is a switch list, the same command
+is forwarded as <tt class="docutils literal"><span class="pre">some-tool</span> <span class="pre">-foo</span> <span class="pre">-foo</span></tt>.</li>
+</ul>
+</blockquote>
+</li>
+<li><p class="first">Possible option properties:</p>
+<blockquote>
+<ul class="simple">
+<li><tt class="docutils literal">help</tt> - help string associated with this option. Used for <tt class="docutils literal"><span class="pre">--help</span></tt>
+output.</li>
+<li><tt class="docutils literal">required</tt> - this option must be specified exactly once (or, in case of
+the list options without the <tt class="docutils literal">multi_val</tt> property, at least
+once). Incompatible with <tt class="docutils literal">optional</tt> and <tt class="docutils literal">one_or_more</tt>.</li>
+<li><tt class="docutils literal">optional</tt> - the option can be specified either zero times or exactly
+once. The default for switch options. Useful only for list options in
+conjunction with <tt class="docutils literal">multi_val</tt>. Incompatible with <tt class="docutils literal">required</tt>,
+<tt class="docutils literal">zero_or_more</tt> and <tt class="docutils literal">one_or_more</tt>.</li>
+<li><tt class="docutils literal">one_or_more</tt> - the option must be specified at least once. Can be useful
+to allow switch options be both obligatory and be specified multiple
+times. For list options is useful only in conjunction with <tt class="docutils literal">multi_val</tt>;
+for ordinary it is synonymous with <tt class="docutils literal">required</tt>. Incompatible with
+<tt class="docutils literal">required</tt>, <tt class="docutils literal">optional</tt> and <tt class="docutils literal">zero_or_more</tt>.</li>
+<li><tt class="docutils literal">zero_or_more</tt> - the option can be specified zero or more times. Useful
+to allow a single switch option to be specified more than
+once. Incompatible with <tt class="docutils literal">required</tt>, <tt class="docutils literal">optional</tt> and <tt class="docutils literal">one_or_more</tt>.</li>
+<li><tt class="docutils literal">hidden</tt> - the description of this option will not appear in
+the <tt class="docutils literal"><span class="pre">--help</span></tt> output (but will appear in the <tt class="docutils literal"><span class="pre">--help-hidden</span></tt>
+output).</li>
+<li><tt class="docutils literal">really_hidden</tt> - the option will not be mentioned in any help
+output.</li>
+<li><tt class="docutils literal">comma_separated</tt> - Indicates that any commas specified for an option's
+value should be used to split the value up into multiple values for the
+option. This property is valid only for list options. In conjunction with
+<tt class="docutils literal">forward_value</tt> can be used to implement option forwarding in style of
+gcc's <tt class="docutils literal"><span class="pre">-Wa,</span></tt>.</li>
+<li><tt class="docutils literal">multi_val n</tt> - this option takes <em>n</em> arguments (can be useful in some
+special cases). Usage example: <tt class="docutils literal">(parameter_list_option "foo", (multi_val
+3))</tt>; the command-line syntax is '-foo a b c'. Only list options can have
+this attribute; you can, however, use the <tt class="docutils literal">one_or_more</tt>, <tt class="docutils literal">optional</tt>
+and <tt class="docutils literal">required</tt> properties.</li>
+<li><tt class="docutils literal">init</tt> - this option has a default value, either a string (if it is a
+parameter), or a boolean (if it is a switch; as in C++, boolean constants
+are called <tt class="docutils literal">true</tt> and <tt class="docutils literal">false</tt>). List options can't have <tt class="docutils literal">init</tt>
+attribute.
+Usage examples: <tt class="docutils literal">(switch_option "foo", (init true))</tt>; <tt class="docutils literal">(prefix_option
+"bar", (init <span class="pre">"baz"))</span></tt>.</li>
+</ul>
+</blockquote>
+</li>
+</ul>
</div>
+<div class="section" id="conditional-evaluation">
+<span id="case"></span><h1><a class="toc-backref" href="#id13">Conditional evaluation</a></h1>
+<p>The 'case' construct is the main means by which programmability is achieved in
+LLVMC. It can be used to calculate edge weights, program actions and modify the
+shell commands to be executed. The 'case' expression is designed after the
+similarly-named construct in functional languages and takes the form <tt class="docutils literal">(case
+(test_1), statement_1, (test_2), statement_2, ... (test_N), statement_N)</tt>. The
+statements are evaluated only if the corresponding tests evaluate to true.</p>
+<p>Examples:</p>
+<pre class="literal-block">
+// Edge weight calculation
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="overview"></a>Overview</div>
-<div class="doc_text">
-<p><tt>llvmc</tt> is highly configurable both on the command line and in
-configuration files. The options it understands are generic, consistent and
-simple by design. Furthermore, the <tt>llvmc</tt> options apply to the
-compilation of any LLVM enabled programming language. To be enabled as a
-supported source language compiler, a compiler writer must provide a
-configuration file that tells <tt>llvmc</tt> how to invoke the compiler
-and what its capabilities are. The purpose of the configuration files then
-is to allow compiler writers to specify to <tt>llvmc</tt> how the compiler
-should be invoked. Users may but are not advised to alter the compiler's
-<tt>llvmc</tt> configuration.</p>
+// Increases edge weight by 5 if "-A" is provided on the
+// command-line, and by 5 more if "-B" is also provided.
+(case
+ (switch_on "A"), (inc_weight 5),
+ (switch_on "B"), (inc_weight 5))
-<p>Because <tt>llvmc</tt> just invokes other programs, it must deal with the
-available command line options for those programs regardless of whether they
-were written for LLVM or not. Furthermore, not all compilation front ends will
-have the same capabilities. Some front ends will simply generate LLVM assembly
-code, others will be able to generate fully optimized byte code. In general,
-<tt>llvmc</tt> doesn't make any assumptions about the capabilities or command
-line options of a sub-tool. It simply uses the details found in the configuration
-files and leaves it to the compiler writer to specify the configuration
-correctly.</p>
-<p>This approach means that new compiler front ends can be up and working very
-quickly. As a first cut, a front end can simply compile its source to raw
-(unoptimized) bytecode or LLVM assembly and <tt>llvmc</tt> can be configured
-to pick up the slack (translate LLVM assembly to bytecode, optimize the
-bytecode, generate native assembly, link, etc.). In fact, the front end need
-not use any LLVM libraries, and it could be written in any language (instead of
-C++). The configuration data will allow the full range of optimization,
-assembly, and linking capabilities that LLVM provides to be added to these kinds
-of tools. Enabling the rapid development of front-ends is one of the primary
-goals of <tt>llvmc</tt>.</p>
+// Tool command line specification
-<p>As a compiler front end matures, it may utilize the LLVM libraries and tools
-to more efficiently produce optimized bytecode directly in a single compilation
-and optimization program. In these cases, multiple tools would not be needed
-and the configuration data for the compiler would change.</p>
+// Evaluates to "cmdline1" if the option "-A" is provided on the
+// command line; to "cmdline2" if "-B" is provided;
+// otherwise to "cmdline3".
-<p>Configuring <tt>llvmc</tt> to the needs and capabilities of a source language
-compiler is relatively straight forward. A compiler writer must provide a
-definition of what to do for each of the five compilation phases for each of
-the optimization levels. The specification consists simply of prototypical
-command lines into which <tt>llvmc</tt> can substitute command line
-arguments and file names. Note that any given phase can be completely blank if
-the source language's compiler combines multiple phases into a single program.
-For example, quite often pre-processing, translation, and optimization are
-combined into a single program. The specification for such a compiler would have
-blank entries for pre-processing and translation but a full command line for
-optimization.</p>
+(case
+ (switch_on "A"), "cmdline1",
+ (switch_on "B"), "cmdline2",
+ (default), "cmdline3")
+</pre>
+<p>Note the slight difference in 'case' expression handling in contexts of edge
+weights and command line specification - in the second example the value of the
+<tt class="docutils literal">"B"</tt> switch is never checked when switch <tt class="docutils literal">"A"</tt> is enabled, and the whole
+expression always evaluates to <tt class="docutils literal">"cmdline1"</tt> in that case.</p>
+<p>Case expressions can also be nested, i.e. the following is legal:</p>
+<pre class="literal-block">
+(case (switch_on "E"), (case (switch_on "o"), ..., (default), ...)
+ (default), ...)
+</pre>
+<p>You should, however, try to avoid doing that because it hurts readability. It is
+usually better to split tool descriptions and/or use TableGen inheritance
+instead.</p>
+<ul class="simple">
+<li>Possible tests are:<ul>
+<li><tt class="docutils literal">switch_on</tt> - Returns true if a given command-line switch is provided by
+the user. Can be given multiple arguments, in that case <tt class="docutils literal">(switch_on "foo",
+"bar", "baz")</tt> is equivalent to <tt class="docutils literal">(and (switch_on <span class="pre">"foo"),</span> (switch_on
+<span class="pre">"bar"),</span> (switch_on <span class="pre">"baz"))</span></tt>.
+Example: <tt class="docutils literal">(switch_on "opt")</tt>.</li>
+<li><tt class="docutils literal">any_switch_on</tt> - Given a number of switch options, returns true if any of
+the switches is turned on.
+Example: <tt class="docutils literal">(any_switch_on "foo", "bar", "baz")</tt> is equivalent to <tt class="docutils literal">(or
+(switch_on <span class="pre">"foo"),</span> (switch_on <span class="pre">"bar"),</span> (switch_on <span class="pre">"baz"))</span></tt>.</li>
+<li><tt class="docutils literal">parameter_equals</tt> - Returns true if a command-line parameter (first
+argument) equals a given value (second argument).
+Example: <tt class="docutils literal">(parameter_equals "W", "all")</tt>.</li>
+<li><tt class="docutils literal">element_in_list</tt> - Returns true if a command-line parameter list (first
+argument) contains a given value (second argument).
+Example: <tt class="docutils literal">(element_in_list "l", "pthread")</tt>.</li>
+<li><tt class="docutils literal">input_languages_contain</tt> - Returns true if a given language
+belongs to the current input language set.
+Example: <tt class="docutils literal">(input_languages_contain <span class="pre">"c++")</span></tt>.</li>
+<li><tt class="docutils literal">in_language</tt> - Evaluates to true if the input file language is equal to
+the argument. At the moment works only with <tt class="docutils literal">command</tt> and <tt class="docutils literal">actions</tt> (on
+non-join nodes).
+Example: <tt class="docutils literal">(in_language <span class="pre">"c++")</span></tt>.</li>
+<li><tt class="docutils literal">not_empty</tt> - Returns true if a given option (which should be either a
+parameter or a parameter list) is set by the user. Like <tt class="docutils literal">switch_on</tt>, can
+be also given multiple arguments.
+Examples: <tt class="docutils literal">(not_empty "o")</tt>, <tt class="docutils literal">(not_empty "o", "l")</tt>.</li>
+<li><tt class="docutils literal">any_not_empty</tt> - Returns true if <tt class="docutils literal">not_empty</tt> returns true for any of
+the provided options.
+Example: <tt class="docutils literal">(any_not_empty "foo", "bar", "baz")</tt> is equivalent to <tt class="docutils literal">(or
+(not_empty <span class="pre">"foo"),</span> (not_empty <span class="pre">"bar"),</span> (not_empty <span class="pre">"baz"))</span></tt>.</li>
+<li><tt class="docutils literal">empty</tt> - The opposite of <tt class="docutils literal">not_empty</tt>. Equivalent to <tt class="docutils literal">(not (not_empty
+X))</tt>. Can be given multiple arguments.</li>
+<li><tt class="docutils literal">any_not_empty</tt> - Returns true if <tt class="docutils literal">not_empty</tt> returns true for any of
+the provided options.
+Example: <tt class="docutils literal">(any_empty "foo", "bar", "baz")</tt> is equivalent to <tt class="docutils literal">(or
+(not_empty <span class="pre">"foo"),</span> (not_empty <span class="pre">"bar"),</span> (not_empty <span class="pre">"baz"))</span></tt>.</li>
+<li><tt class="docutils literal">single_input_file</tt> - Returns true if there was only one input file
+provided on the command-line. Used without arguments:
+<tt class="docutils literal">(single_input_file)</tt>.</li>
+<li><tt class="docutils literal">multiple_input_files</tt> - Equivalent to <tt class="docutils literal">(not (single_input_file))</tt> (the
+case of zero input files is considered an error).</li>
+<li><tt class="docutils literal">default</tt> - Always evaluates to true. Should always be the last
+test in the <tt class="docutils literal">case</tt> expression.</li>
+<li><tt class="docutils literal">and</tt> - A standard logical combinator that returns true iff all of
+its arguments return true. Used like this: <tt class="docutils literal">(and (test1), (test2),
+... (testN))</tt>. Nesting of <tt class="docutils literal">and</tt> and <tt class="docutils literal">or</tt> is allowed, but not
+encouraged.</li>
+<li><tt class="docutils literal">or</tt> - A logical combinator that returns true iff any of its arguments
+return true.
+Example: <tt class="docutils literal">(or (test1), (test2), ... (testN))</tt>.</li>
+<li><tt class="docutils literal">not</tt> - Standard unary logical combinator that negates its
+argument.
+Example: <tt class="docutils literal">(not (or (test1), (test2), ... <span class="pre">(testN)))</span></tt>.</li>
+</ul>
+</li>
+</ul>
</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="filetypes"></a>Configuration Files</div>
-<div class="doc_text">
- <h3>File Types</h3>
- <p>There are two types of configuration files: the master configuration file
- and the language specific configuration file. The master configuration file
- contains the general configuration of <tt>llvmc</tt> itself and is supplied
- with the tool. It contains information that is source language agnostic.
- Language specific configuration files tell <tt>llvmc</tt> how to invoke the
- language's compiler for a variety of different tasks and what other tools
- are needed to backfill the compiler's missing features (e.g.
- optimization).</p>
-
- <h3>Directory Search</h3>
- <p><tt>llvmc</tt> always looks for files of a specific name. It uses the
- first file with the name its looking for by searching directories in the
- following order:<br/>
- <ol>
- <li>Any directory specified by the <tt>--config-dir</tt> option will be
- checked first.</li>
- <li>If the environment variable LLVM_CONFIG_DIR is set, and it contains
- the name of a valid directory, that directory will be searched next.</li>
- <li>If the user's home directory (typically <tt>/home/user</tt> contains
- a sub-directory named <tt>.llvm</tt> and that directory contains a
- sub-directory named <tt>etc</tt> then that directory will be tried
- next.</li>
- <li>If the LLVM installation directory (typically <tt>/usr/local/llvm</tt>
- contains a sub-directory named <tt>etc</tt> then that directory will be
- tried last.</li>
- <li>If the configuration file sought still can't be found, <tt>llvmc</tt>
- will print an error message and exit.</li>
- </ol>
- The first file found in this search will be used. Other files with the same
- name will be ignored even if they exist in one of the subsequent search
- locations.</p>
-
- <h3>File Names</h3>
- <p>In the directories searched, a file named <tt>master</tt> will be
- recognized as the master configuration file for <tt>llvmc</tt>. Note that
- users <i>may</i> override the master file with a copy in their home directory
- but they are advised not to. This capability is only useful for compiler
- implementers needing to alter the master configuration while developing
- their compiler front end. When reading the configuration files, the master
- files are always read first.</p>
- <p>Language specific configuration files are given specific names to foster
- faster lookup. The name of a given language specific configuration file is
- the same as the suffix used to identify files containing source in that
- language. For example, a configuration file for C++ source might be named
- <tt>cpp</tt>, <tt>C</tt>, or <tt>cxx</tt>.</p>
-
- <h3>What Gets Read</h3>
- <p>The master configuration file is always read. Which language specific
- configuration files are read depends on the command line options and the
- suffixes of the file names provided on <tt>llvmc</tt>'s command line. Note
- that the <tt>--x LANGUAGE</tt> option alters the language that <tt>llvmc</tt>
- uses for the subsequent files on the command line. Only the language
- specific configuration files actually needed to complete <tt>llvmc</tt>'s
- task are read. Other language specific files will be ignored.</p>
+<div class="section" id="writing-a-tool-description">
+<h1><a class="toc-backref" href="#id14">Writing a tool description</a></h1>
+<p>As was said earlier, nodes in the compilation graph represent tools, which are
+described separately. A tool definition looks like this (taken from the
+<tt class="docutils literal">llvmc/src/Base.td</tt> file):</p>
+<pre class="literal-block">
+def llvm_gcc_cpp : Tool<[
+ (in_language "c++"),
+ (out_language "llvm-assembler"),
+ (output_suffix "bc"),
+ (command "llvm-g++ -c -emit-llvm"),
+ (sink)
+ ]>;
+</pre>
+<p>This defines a new tool called <tt class="docutils literal">llvm_gcc_cpp</tt>, which is an alias for
+<tt class="docutils literal"><span class="pre">llvm-g++</span></tt>. As you can see, a tool definition is just a list of properties;
+most of them should be self-explanatory. The <tt class="docutils literal">sink</tt> property means that this
+tool should be passed all command-line options that aren't mentioned in the
+option list.</p>
+<p>The complete list of all currently implemented tool properties follows.</p>
+<ul class="simple">
+<li>Possible tool properties:<ul>
+<li><tt class="docutils literal">in_language</tt> - input language name. Can be given multiple arguments, in
+case the tool supports multiple input languages. Used for typechecking and
+mapping file extensions to tools.</li>
+<li><tt class="docutils literal">out_language</tt> - output language name. Multiple output languages are
+allowed. Used for typechecking the compilation graph.</li>
+<li><tt class="docutils literal">output_suffix</tt> - output file suffix. Can also be changed dynamically, see
+documentation on <a class="reference internal" href="#actions">actions</a>.</li>
+</ul>
+</li>
+</ul>
+<blockquote>
+<ul class="simple">
+<li><tt class="docutils literal">command</tt> - the actual command used to run the tool. You can use output
+redirection with <tt class="docutils literal">></tt>, hook invocations (<tt class="docutils literal">$CALL</tt>), environment variables
+(via <tt class="docutils literal">$ENV</tt>) and the <tt class="docutils literal">case</tt> construct.</li>
+<li><tt class="docutils literal">join</tt> - this tool is a "join node" in the graph, i.e. it gets a list of
+input files and joins them together. Used for linkers.</li>
+<li><tt class="docutils literal">sink</tt> - all command-line options that are not handled by other tools are
+passed to this tool.</li>
+<li><tt class="docutils literal">actions</tt> - A single big <tt class="docutils literal">case</tt> expression that specifies how this tool
+reacts on command-line options (described in more detail <a class="reference internal" href="#actions">below</a>).</li>
+</ul>
+</blockquote>
+<blockquote>
+<ul class="simple">
+<li><tt class="docutils literal">out_file_option</tt>, <tt class="docutils literal">in_file_option</tt> - Options appended to the
+<tt class="docutils literal">command</tt> string to designate output and input files. Default values are
+<tt class="docutils literal"><span class="pre">"-o"</span></tt> and <tt class="docutils literal">""</tt>, respectively.</li>
+</ul>
+</blockquote>
+<div class="section" id="id4">
+<span id="actions"></span><h2><a class="toc-backref" href="#id15">Actions</a></h2>
+<p>A tool often needs to react to command-line options, and this is precisely what
+the <tt class="docutils literal">actions</tt> property is for. The next example illustrates this feature:</p>
+<pre class="literal-block">
+def llvm_gcc_linker : Tool<[
+ (in_language "object-code"),
+ (out_language "executable"),
+ (output_suffix "out"),
+ (command "llvm-gcc"),
+ (join),
+ (actions (case (not_empty "L"), (forward "L"),
+ (not_empty "l"), (forward "l"),
+ (not_empty "dummy"),
+ [(append_cmd "-dummy1"), (append_cmd "-dummy2")])
+ ]>;
+</pre>
+<p>The <tt class="docutils literal">actions</tt> tool property is implemented on top of the omnipresent <tt class="docutils literal">case</tt>
+expression. It associates one or more different <em>actions</em> with given
+conditions - in the example, the actions are <tt class="docutils literal">forward</tt>, which forwards a given
+option unchanged, and <tt class="docutils literal">append_cmd</tt>, which appends a given string to the tool
+execution command. Multiple actions can be associated with a single condition by
+using a list of actions (used in the example to append some dummy options). The
+same <tt class="docutils literal">case</tt> construct can also be used in the <tt class="docutils literal">cmd_line</tt> property to modify
+the tool command line.</p>
+<p>The "join" property used in the example means that this tool behaves like a
+linker.</p>
+<p>The list of all possible actions follows.</p>
+<ul>
+<li><p class="first">Possible actions:</p>
+<blockquote>
+<ul class="simple">
+<li><tt class="docutils literal">append_cmd</tt> - Append a string to the tool invocation command.
+Example: <tt class="docutils literal">(case (switch_on <span class="pre">"pthread"),</span> (append_cmd <span class="pre">"-lpthread"))</span></tt>.</li>
+<li><tt class="docutils literal">error</tt> - Exit with error.
+Example: <tt class="docutils literal">(error "Mixing <span class="pre">-c</span> and <span class="pre">-S</span> is not <span class="pre">allowed!")</span></tt>.</li>
+<li><tt class="docutils literal">warning</tt> - Print a warning.
+Example: <tt class="docutils literal">(warning "Specifying both <span class="pre">-O1</span> and <span class="pre">-O2</span> is <span class="pre">meaningless!")</span></tt>.</li>
+<li><tt class="docutils literal">forward</tt> - Forward the option unchanged.
+Example: <tt class="docutils literal">(forward "Wall")</tt>.</li>
+<li><tt class="docutils literal">forward_as</tt> - Change the option's name, but forward the argument
+unchanged.
+Example: <tt class="docutils literal">(forward_as "O0", <span class="pre">"--disable-optimization")</span></tt>.</li>
+<li><tt class="docutils literal">forward_value</tt> - Forward only option's value. Cannot be used with switch
+options (since they don't have values), but works fine with lists.
+Example: <tt class="docutils literal">(forward_value <span class="pre">"Wa,")</span></tt>.</li>
+<li><tt class="docutils literal">forward_transformed_value</tt> - As above, but applies a hook to the
+option's value before forwarding (see <a class="reference internal" href="#hooks">below</a>). When
+<tt class="docutils literal">forward_transformed_value</tt> is applied to a list
+option, the hook must have signature
+<tt class="docutils literal"><span class="pre">std::string</span> <span class="pre">hooks::HookName</span> (const <span class="pre">std::vector<std::string>&)</span></tt>.
+Example: <tt class="docutils literal">(forward_transformed_value "m", "ConvertToMAttr")</tt>.</li>
+<li><tt class="docutils literal">output_suffix</tt> - Modify the output suffix of this tool.
+Example: <tt class="docutils literal">(output_suffix "i")</tt>.</li>
+<li><tt class="docutils literal">stop_compilation</tt> - Stop compilation after this tool processes its
+input. Used without arguments.
+Example: <tt class="docutils literal">(stop_compilation)</tt>.</li>
+</ul>
+</blockquote>
+</li>
+</ul>
</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="syntax"></a>Syntax</div>
-<div class="doc_text">
- <p>The syntax of the configuration files is yet to be determined. There are
- two viable options remaining:<br/>
- <ul>
- <li>XML DTD Specific To <tt>llvmc</tt></li>
- <li>Windows .ini style file with numerous sections</li>
- </ul></p>
</div>
-
-<!-- _______________________________________________________________________ -->
-<div class="doc_subsection"><a name="master_items">Configuration Items</a></div>
-<div class="doc_text">
- <p>The following description of configuration items is syntax-less and simply
- uses a naming hierarchy to describe the configuration items. Whatever
- syntax is chosen will need to map the hierarchy to the given syntax.</p>
- <table>
- <tr>
- <th>Name</th>
- <th>Value Type</th>
- <th>Description</th>
- </tr>
- <tr>
- <td><b>Capabilities.hasPreProcessor</b></td>
- <td>boolean</td>
- <td class="td_left">This item specifies whether the language has a
- pre-processing phase or not. This controls whether the B<-E> option works
- for the language or not.</td>
- </tr>
- <tr>
- <td><b>Capabilities.outputFormat</b></td>
- <td>"bc" or "ll"</td>
- <td class="td_left">This item specifies the kind of output the language's
- compiler generates. The choices are either bytecode (<tt>bc</tt>) or LLVM
- assembly (<tt>ll</tt>).</td>
- </tr>
- <tr>
- <td><b>Capabilities.understandsOptimization</b></td>
- <td>boolean</td>
- <td>Indicates whether the compiler for this language understands the
- <tt>-O</tt> options or not</td>
- </tr>
- </table>
+<div class="section" id="language-map">
+<h1><a class="toc-backref" href="#id16">Language map</a></h1>
+<p>If you are adding support for a new language to LLVMC, you'll need to modify the
+language map, which defines mappings from file extensions to language names. It
+is used to choose the proper toolchain(s) for a given input file set. Language
+map definition looks like this:</p>
+<pre class="literal-block">
+def LanguageMap : LanguageMap<
+ [LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>,
+ LangToSuffixes<"c", ["c"]>,
+ ...
+ ]>;
+</pre>
+<p>For example, without those definitions the following command wouldn't work:</p>
+<pre class="literal-block">
+$ llvmc hello.cpp
+llvmc: Unknown suffix: cpp
+</pre>
+<p>The language map entries are needed only for the tools that are linked from the
+root node. A tool can have multiple output languages.</p>
</div>
+<div class="section" id="option-preprocessor">
+<h1><a class="toc-backref" href="#id17">Option preprocessor</a></h1>
+<p>It is sometimes useful to run error-checking code before processing the
+compilation graph. For example, if optimization options "-O1" and "-O2" are
+implemented as switches, we might want to output a warning if the user invokes
+the driver with both of these options enabled.</p>
+<p>The <tt class="docutils literal">OptionPreprocessor</tt> feature is reserved specially for these
+occasions. Example (adapted from <tt class="docutils literal">llvm/src/Base.td.in</tt>):</p>
+<pre class="literal-block">
+def Preprocess : OptionPreprocessor<
+(case (not (any_switch_on "O0", "O1", "O2", "O3")),
+ (set_option "O2"),
+ (and (switch_on "O3"), (any_switch_on "O0", "O1", "O2")),
+ (unset_option "O0", "O1", "O2"),
+ (and (switch_on "O2"), (any_switch_on "O0", "O1")),
+ (unset_option "O0", "O1"),
+ (and (switch_on "O1"), (switch_on "O0")),
+ (unset_option "O0"))
+>;
+</pre>
+<p>Here, <tt class="docutils literal">OptionPreprocessor</tt> is used to unset all spurious <tt class="docutils literal"><span class="pre">-O</span></tt> options so
+that they are not forwarded to the compiler. If no optimization options are
+specified, <tt class="docutils literal"><span class="pre">-O2</span></tt> is enabled.</p>
+<p><tt class="docutils literal">OptionPreprocessor</tt> is basically a single big <tt class="docutils literal">case</tt> expression, which is
+evaluated only once right after the driver is started. The only allowed actions
+in <tt class="docutils literal">OptionPreprocessor</tt> are <tt class="docutils literal">error</tt>, <tt class="docutils literal">warning</tt>, and two special actions:
+<tt class="docutils literal">unset_option</tt> and <tt class="docutils literal">set_option</tt>. As their names suggest, they can be used to
+set or unset a given option. To set an option with <tt class="docutils literal">set_option</tt>, use the
+two-argument form: <tt class="docutils literal">(set_option "parameter", VALUE)</tt>. Here, <tt class="docutils literal">VALUE</tt> can be
+either a string, a string list, or a boolean constant.</p>
+<p>For convenience, <tt class="docutils literal">set_option</tt> and <tt class="docutils literal">unset_option</tt> also work with multiple
+arguments. That is, instead of <tt class="docutils literal">[(unset_option <span class="pre">"A"),</span> (unset_option <span class="pre">"B")]</span></tt> you
+can use <tt class="docutils literal">(unset_option "A", "B")</tt>. Obviously, <tt class="docutils literal">(set_option "A", "B")</tt> is
+only valid if both <tt class="docutils literal">A</tt> and <tt class="docutils literal">B</tt> are switches.</p>
+</div>
+<div class="section" id="more-advanced-topics">
+<h1><a class="toc-backref" href="#id18">More advanced topics</a></h1>
+<div class="section" id="hooks-and-environment-variables">
+<span id="hooks"></span><h2><a class="toc-backref" href="#id19">Hooks and environment variables</a></h2>
+<p>Normally, LLVMC searches for programs in the system <tt class="docutils literal">PATH</tt>. Sometimes, this is
+not sufficient: for example, we may want to specify tool paths or names in the
+configuration file. This can be achieved via the hooks mechanism. To write your
+own hooks, add their definitions to the <tt class="docutils literal">Hooks.cpp</tt> or drop a <tt class="docutils literal">.cpp</tt> file
+into your driver directory. Hooks should live in the <tt class="docutils literal">hooks</tt> namespace and
+have the signature <tt class="docutils literal"><span class="pre">std::string</span> <span class="pre">hooks::MyHookName</span> ([const char* Arg0 [ const
+char* Arg2 [, <span class="pre">...]]])</span></tt>. They can be used from the <tt class="docutils literal">command</tt> tool property:</p>
+<pre class="literal-block">
+(command "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)")
+</pre>
+<p>To pass arguments to hooks, use the following syntax:</p>
+<pre class="literal-block">
+(command "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2")
+</pre>
+<p>It is also possible to use environment variables in the same manner:</p>
+<pre class="literal-block">
+(command "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
+</pre>
+<p>To change the command line string based on user-provided options use
+the <tt class="docutils literal">case</tt> expression (documented <a class="reference internal" href="#case">above</a>):</p>
+<pre class="literal-block">
+(command
+ (case
+ (switch_on "E"),
+ "llvm-g++ -E -x c $INFILE -o $OUTFILE",
+ (default),
+ "llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm"))
+</pre>
+</div>
+<div class="section" id="debugging">
+<h2><a class="toc-backref" href="#id20">Debugging</a></h2>
+<p>When writing LLVMC-based drivers, it can be useful to get a visual view of the
+resulting compilation graph. This can be achieved via the command line option
+<tt class="docutils literal"><span class="pre">--view-graph</span></tt> (which assumes that <a class="reference external" href="http://www.graphviz.org/">Graphviz</a> and <a class="reference external" href="http://pages.cs.wisc.edu/~ghost/">Ghostview</a> are
+installed). There is also a <tt class="docutils literal"><span class="pre">--write-graph</span></tt> option that creates a Graphviz
+source file (<tt class="docutils literal"><span class="pre">compilation-graph.dot</span></tt>) in the current directory.</p>
+<p>Another useful <tt class="docutils literal">llvmc</tt> option is <tt class="docutils literal"><span class="pre">--check-graph</span></tt>. It checks the compilation
+graph for common errors like mismatched output/input language names, multiple
+default edges and cycles. When invoked with <tt class="docutils literal"><span class="pre">--check-graph</span></tt>, <tt class="docutils literal">llvmc</tt> doesn't
+perform any compilation tasks and returns the number of encountered errors as
+its status code. In the future, these checks will be performed at compile-time
+and this option will disappear.</p>
+</div>
+<div class="section" id="conditioning-on-the-executable-name">
+<h2><a class="toc-backref" href="#id21">Conditioning on the executable name</a></h2>
+<p>For now, the executable name (the value passed to the driver in <tt class="docutils literal">argv[0]</tt>) is
+accessible only in the C++ code (i.e. hooks). Use the following code:</p>
+<pre class="literal-block">
+namespace llvmc {
+extern const char* ProgramName;
+}
-<!-- *********************************************************************** -->
-<div class="doc_section"><a name="glossary">Glossary</a></div>
-<!-- *********************************************************************** -->
-<div class="doc_text">
- <p>This document uses precise terms in reference to the various artifacts and
- concepts related to compilation. The terms used throughout this document are
- defined below.</p>
- <dl>
- <dt><a name="def_assembly"><b>assembly</b></a></dt>
- <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode or
- LLVM assembly code is assembled to a native code format (either target
- specific aseembly language or the platform's native object file format).
- </dd>
-
- <dt><a name="def_compiler"><b>compiler</b></a></dt>
- <dd>Refers to any program that can be invoked by <tt>llvmc</tt> to accomplish
- the work of one or more compilation <a href="#def_phase">phases</a>.</dd>
-
- <dt><a name="def_driver"><b>driver</b></a></dt>
- <dd>Refers to <tt>llvmc</tt> itself.</dd>
-
- <dt><a name="def_linking"><b>linking</b></a></dt>
- <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode files
- and (optionally) native system libraries are combined to form a complete
- executable program.</dd>
+namespace hooks {
- <dt><a name="def_optimization"><b>optimization</b></a></dt>
- <dd>A compilation <a href="#def_phase">phase</a> in which LLVM bytecode is
- optimized.</dd>
+std::string MyHook() {
+//...
+if (strcmp(ProgramName, "mydriver") == 0) {
+ //...
- <dt><a name="def_phase"><b>phase</b></a></dt>
- <dd>Refers to any one of the five compilation phases that that
- <tt>llvmc</tt> supports. The five phases are:
- <a href="#def_preprocessing">preprocessing</a>,
- <a href="#def_translation">translation</a>,
- <a href="#def_optimization">optimization</a>,
- <a href="#def_assembly">assembly</a>,
- <a href="#def_linking">linking</a>.</dd>
+}
- <dt><a name="def_sourcelanguage"><b>source language</b></a></dt>
- <dd>Any common programming language (e.g. C, C++, Java, Stacker, ML,
- FORTRAN). These languages are distinguished from any of the lower level
- languages (such as LLVM or native assembly), by the fact that a
- <a href="#def_translation">translation</a> <a href="#def_phase">phase</a>
- is required before LLVM can be applied.</dd>
+} // end namespace hooks
+</pre>
+<p>In general, you're encouraged not to make the behaviour dependent on the
+executable file name, and use command-line switches instead. See for example how
+the <tt class="docutils literal">llvmc</tt> program behaves when it needs to choose the correct linker options
+(think <tt class="docutils literal">g++</tt> vs. <tt class="docutils literal">gcc</tt>).</p>
+<hr />
+<address>
+<a href="http://jigsaw.w3.org/css-validator/check/referer">
+<img src="http://jigsaw.w3.org/css-validator/images/vcss-blue"
+ alt="Valid CSS" /></a>
+<a href="http://validator.w3.org/check?uri=referer">
+<img src="http://www.w3.org/Icons/valid-xhtml10-blue"
+ alt="Valid XHTML 1.0 Transitional"/></a>
- <dt><a name="def_tool"><b>tool</b></a></dt>
- <dd>Refers to any program in the LLVM tool set.</dd>
+<a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a><br />
+<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br />
- <dt><a name="def_translation"><b>translation</b></a></dt>
- <dd>A compilation <a href="#def_phase">phase</a> in which
- <a href="#def_sourcelanguage">source language</a> code is translated into
- either LLVM assembly language or LLVM bytecode.</dd>
- </dl>
-</div>
-<!-- *********************************************************************** -->
-<hr>
-<address> <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
- src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a><a
- href="http://validator.w3.org/check/referer"><img
- src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a><a
- href="mailto:rspencer@x10sys.com">Reid Spencer</a><br>
-<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
-</address>
-<!-- vim: sw=2
--->
+</address></div>
+</div>
+</div>
</body>
</html>
projects / oota-llvm.git / blobdiff