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| author | mike-m <mikem.llvm@gmail.com> | 2010-05-07 00:28:04 +0000 |
|---|---|---|
| committer | mike-m <mikem.llvm@gmail.com> | 2010-05-07 00:28:04 +0000 |
| commit | e2c3a49c8029ebd9ef530101cc24c66562e3dff5 (patch) | |
| tree | 91bf9600cc8df90cf99751a8f8bafc317cffc91e /docs/CompilerDriver.html | |
| parent | c10b5afbe8138b0fdf3af4ed3e1ddf96cf3cb4cb (diff) | |
Revert r103213. It broke several sections of live website.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103219 91177308-0d34-0410-b5e6-96231b3b80d8
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diff --git a/docs/CompilerDriver.html b/docs/CompilerDriver.html new file mode 100644 index 0000000000..3c82e2b076 --- /dev/null +++ b/docs/CompilerDriver.html @@ -0,0 +1,756 @@ +<?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" /> +<meta name="generator" content="Docutils 0.5: http://docutils.sourceforge.net/" /> +<title>Customizing LLVMC: Reference Manual</title> +<link rel="stylesheet" href="llvm.css" type="text/css" /> +</head> +<body> +<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="id8">Introduction</a></li> +<li><a class="reference internal" href="#compiling-with-llvmc" id="id9">Compiling with LLVMC</a></li> +<li><a class="reference internal" href="#predefined-options" id="id10">Predefined options</a></li> +<li><a class="reference internal" href="#compiling-llvmc-plugins" id="id11">Compiling LLVMC plugins</a></li> +<li><a class="reference internal" href="#compiling-standalone-llvmc-based-drivers" id="id12">Compiling standalone LLVMC-based drivers</a></li> +<li><a class="reference internal" href="#customizing-llvmc-the-compilation-graph" id="id13">Customizing LLVMC: the compilation graph</a></li> +<li><a class="reference internal" href="#describing-options" id="id14">Describing options</a><ul> +<li><a class="reference internal" href="#external-options" id="id15">External options</a></li> +</ul> +</li> +<li><a class="reference internal" href="#conditional-evaluation" id="id16">Conditional evaluation</a></li> +<li><a class="reference internal" href="#writing-a-tool-description" id="id17">Writing a tool description</a><ul> +<li><a class="reference internal" href="#id5" id="id18">Actions</a></li> +</ul> +</li> +<li><a class="reference internal" href="#language-map" id="id19">Language map</a></li> +<li><a class="reference internal" href="#option-preprocessor" id="id20">Option preprocessor</a></li> +<li><a class="reference internal" href="#more-advanced-topics" id="id21">More advanced topics</a><ul> +<li><a class="reference internal" href="#hooks-and-environment-variables" id="id22">Hooks and environment variables</a></li> +<li><a class="reference internal" href="#how-plugins-are-loaded" id="id23">How plugins are loaded</a></li> +<li><a class="reference internal" href="#debugging" id="id24">Debugging</a></li> +<li><a class="reference internal" href="#conditioning-on-the-executable-name" id="id25">Conditioning on the executable name</a></li> +</ul> +</li> +</ul> +</div> +<div class="doc_author"> +<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="#id8">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"><span class="pre">gcc</span></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 completely determined +by plugins, which can be either statically or dynamically linked. This +makes it possible to easily 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="section" id="compiling-with-llvmc"> +<h1><a class="toc-backref" href="#id9">Compiling with LLVMC</a></h1> +<p>LLVMC tries hard to be as compatible with <tt class="docutils literal"><span class="pre">gcc</span></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"><span class="pre">g++</span></tt> vs. <tt class="docutils literal"><span class="pre">gcc</span></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"><span class="pre">gcc</span></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"><span class="pre">clang</span></tt> compiler with the <tt class="docutils literal"><span class="pre">-clang</span></tt> option.</p> +</div> +<div class="section" id="predefined-options"> +<h1><a class="toc-backref" href="#id10">Predefined options</a></h1> +<p>LLVMC has some built-in options that can't be overridden in the +configuration libraries:</p> +<ul class="simple"> +<li><tt class="docutils literal"><span class="pre">-o</span> <span class="pre">FILE</span></tt> - Output file name.</li> +<li><tt class="docutils literal"><span class="pre">-x</span> <span class="pre">LANGUAGE</span></tt> - Specify the language of the following input files +until the next -x option.</li> +<li><tt class="docutils literal"><span class="pre">-load</span> <span class="pre">PLUGIN_NAME</span></tt> - Load the specified plugin DLL. Example: +<tt class="docutils literal"><span class="pre">-load</span> <span class="pre">$LLVM_DIR/Release/lib/LLVMCSimple.so</span></tt>.</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> <span class="pre">DIRECTORY</span></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. Because of +plugins, these checks can't be performed at compile-time. Exit with code zero +if no errors were found, and return the number of found errors +otherwise. Hidden option, useful for debugging LLVMC plugins.</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"><span class="pre">dot</span></tt> and <tt class="docutils literal"><span class="pre">gv</span></tt> programs installed. Hidden +option, useful for debugging LLVMC plugins.</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 LLVMC +plugins.</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="section" id="compiling-llvmc-plugins"> +<h1><a class="toc-backref" href="#id11">Compiling LLVMC plugins</a></h1> +<p>It's easiest to start working on your own LLVMC plugin by copying the +skeleton project which lives under <tt class="docutils literal"><span class="pre">$LLVMC_DIR/plugins/Simple</span></tt>:</p> +<pre class="literal-block"> +$ cd $LLVMC_DIR/plugins +$ cp -r Simple MyPlugin +$ cd MyPlugin +$ ls +Makefile PluginMain.cpp Simple.td +</pre> +<p>As you can see, our basic plugin consists of only two files (not +counting the build script). <tt class="docutils literal"><span class="pre">Simple.td</span></tt> contains TableGen +description of the compilation graph; its format is documented in the +following sections. <tt class="docutils literal"><span class="pre">PluginMain.cpp</span></tt> is just a helper file used to +compile the auto-generated C++ code produced from TableGen source. It +can also contain hook definitions (see <a class="reference internal" href="#hooks">below</a>).</p> +<p>The first thing that you should do is to change the <tt class="docutils literal"><span class="pre">LLVMC_PLUGIN</span></tt> +variable in the <tt class="docutils literal"><span class="pre">Makefile</span></tt> to avoid conflicts (since this variable +is used to name the resulting library):</p> +<pre class="literal-block"> +LLVMC_PLUGIN=MyPlugin +</pre> +<p>It is also a good idea to rename <tt class="docutils literal"><span class="pre">Simple.td</span></tt> to something less +generic:</p> +<pre class="literal-block"> +$ mv Simple.td MyPlugin.td +</pre> +<p>To build your plugin as a dynamic library, just <tt class="docutils literal"><span class="pre">cd</span></tt> to its source +directory and run <tt class="docutils literal"><span class="pre">make</span></tt>. The resulting file will be called +<tt class="docutils literal"><span class="pre">plugin_llvmc_$(LLVMC_PLUGIN).$(DLL_EXTENSION)</span></tt> (in our case, +<tt class="docutils literal"><span class="pre">plugin_llvmc_MyPlugin.so</span></tt>). This library can be then loaded in with the +<tt class="docutils literal"><span class="pre">-load</span></tt> option. Example:</p> +<pre class="literal-block"> +$ cd $LLVMC_DIR/plugins/Simple +$ make +$ llvmc -load $LLVM_DIR/Release/lib/plugin_llvmc_Simple.so +</pre> +</div> +<div class="section" id="compiling-standalone-llvmc-based-drivers"> +<h1><a class="toc-backref" href="#id12">Compiling standalone LLVMC-based drivers</a></h1> +<p>By default, the <tt class="docutils literal"><span class="pre">llvmc</span></tt> executable consists of a driver core plus several +statically linked plugins (<tt class="docutils literal"><span class="pre">Base</span></tt> and <tt class="docutils literal"><span class="pre">Clang</span></tt> at the moment). You can +produce a standalone LLVMC-based driver executable by linking the core with your +own plugins. The recommended way to do this is by starting with the provided +<tt class="docutils literal"><span class="pre">Skeleton</span></tt> example (<tt class="docutils literal"><span class="pre">$LLVMC_DIR/example/Skeleton</span></tt>):</p> +<pre class="literal-block"> +$ cd $LLVMC_DIR/example/ +$ cp -r Skeleton mydriver +$ cd mydriver +$ vim Makefile +[...] +$ make +</pre> +<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"><span class="pre">make</span></tt>:</p> +<pre class="literal-block"> +# LLVMC_SRC_DIR = $LLVM_SRC_DIR/tools/llvmc/ +# LLVMC_OBJ_DIR = $LLVM_OBJ_DIR/tools/llvmc/ +$ cp $LLVMC_SRC_DIR/example/mydriver/Makefile \ + $LLVMC_OBJ_DIR/example/mydriver/ +$ cd $LLVMC_OBJ_DIR/example/mydriver +$ make +</pre> +<p>Another way to do the same thing is by using the following command:</p> +<pre class="literal-block"> +$ cd $LLVMC_DIR +$ make LLVMC_BUILTIN_PLUGINS=MyPlugin LLVMC_BASED_DRIVER_NAME=mydriver +</pre> +<p>This works with both srcdir == objdir and srcdir != objdir, but assumes that the +plugin source directory was placed under <tt class="docutils literal"><span class="pre">$LLVMC_DIR/plugins</span></tt>.</p> +<p>Sometimes, you will want a 'bare-bones' version of LLVMC that has no +built-in plugins. It can be compiled with the following command:</p> +<pre class="literal-block"> +$ cd $LLVMC_DIR +$ make LLVMC_BUILTIN_PLUGINS="" +</pre> +</div> +<div class="section" id="customizing-llvmc-the-compilation-graph"> +<h1><a class="toc-backref" href="#id13">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"><span class="pre">plugins/Base/Base.td</span></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">, + ... + + Edge<"llvm_gcc_c", "llc">, + Edge<"llvm_gcc_cpp", "llc">, + ... + + OptionalEdge<"llvm_gcc_c", "opt", (case (switch_on "opt"), + (inc_weight))>, + OptionalEdge<"llvm_gcc_cpp", "opt", (case (switch_on "opt"), + (inc_weight))>, + ... + + 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))>, + ... + + ]>; +</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"><span class="pre">case</span></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 in plugins 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"><span class="pre">case</span></tt> expression. It is also possible to provide an +integer parameter to <tt class="docutils literal"><span class="pre">inc_weight</span></tt> and <tt class="docutils literal"><span class="pre">dec_weight</span></tt> - in this case, +the weight is increased (or decreased) by the provided value instead +of the default 2. It is also possible to change the default weight of +an optional edge by using the <tt class="docutils literal"><span class="pre">default</span></tt> clause of the <tt class="docutils literal"><span class="pre">case</span></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 plugins are loaded, their compilation graphs are merged +together. Since multiple edges that have the same end nodes are not +allowed (i.e. the graph is not a multigraph), an edge defined in +several plugins will be replaced by the definition from the plugin +that was loaded last. Plugin load order can be controlled by using the +plugin priority feature described above.</p> +<p>To get a visual representation of the compilation graph (useful for +debugging), run <tt class="docutils literal"><span class="pre">llvmc</span> <span class="pre">--view-graph</span></tt>. You will need <tt class="docutils literal"><span class="pre">dot</span></tt> and +<tt class="docutils literal"><span class="pre">gsview</span></tt> installed for this to work properly.</p> +</div> +<div class="section" id="describing-options"> +<h1><a class="toc-backref" href="#id14">Describing options</a></h1> +<p>Command-line options that the plugin supports are defined by using an +<tt class="docutils literal"><span class="pre">OptionList</span></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. A plugin can define more than one option list (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"><span class="pre">switch_option</span></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.</li> +<li><tt class="docutils literal"><span class="pre">parameter_option</span></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> <span class="pre">c99</span></tt>. At most one occurrence is allowed.</li> +<li><tt class="docutils literal"><span class="pre">parameter_list_option</span></tt> - same as the above, but more than one option +occurence is allowed.</li> +<li><tt class="docutils literal"><span class="pre">prefix_option</span></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> <span class="pre">file</span></tt>; however, <tt class="docutils literal"><span class="pre">-o=file</span></tt> will be parsed incorrectly +(<tt class="docutils literal"><span class="pre">=file</span></tt> will be interpreted as option value). At most one occurrence is +allowed.</li> +<li><tt class="docutils literal"><span class="pre">prefix_list_option</span></tt> - same as the above, but more than one occurence 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"><span class="pre">alias_option</span></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"><span class="pre">(alias_option</span> <span class="pre">"preprocess",</span> <span class="pre">"E")</span></tt></li> +</ul> +</blockquote> +</li> +<li><p class="first">Possible option properties:</p> +<blockquote> +<ul class="simple"> +<li><tt class="docutils literal"><span class="pre">help</span></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"><span class="pre">required</span></tt> - this option must be specified exactly once (or, in case of +the list options without the <tt class="docutils literal"><span class="pre">multi_val</span></tt> property, at least +once). Incompatible with <tt class="docutils literal"><span class="pre">zero_or_one</span></tt> and <tt class="docutils literal"><span class="pre">one_or_more</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">one_or_more</span></tt> - the option must be specified at least one time. Useful +only for list options in conjunction with <tt class="docutils literal"><span class="pre">multi_val</span></tt>; for ordinary lists +it is synonymous with <tt class="docutils literal"><span class="pre">required</span></tt>. Incompatible with <tt class="docutils literal"><span class="pre">required</span></tt> and +<tt class="docutils literal"><span class="pre">zero_or_one</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">optional</span></tt> - the option can be specified zero or one times. Useful only +for list options in conjunction with <tt class="docutils literal"><span class="pre">multi_val</span></tt>. Incompatible with +<tt class="docutils literal"><span class="pre">required</span></tt> and <tt class="docutils literal"><span class="pre">one_or_more</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">hidden</span></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"><span class="pre">really_hidden</span></tt> - the option will not be mentioned in any help +output.</li> +<li><tt class="docutils literal"><span class="pre">comma_separated</span></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"><span class="pre">forward_value</span></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"><span class="pre">multi_val</span> <span class="pre">n</span></tt> - this option takes <em>n</em> arguments (can be useful in some +special cases). Usage example: <tt class="docutils literal"><span class="pre">(parameter_list_option</span> <span class="pre">"foo",</span> <span class="pre">(multi_val</span> +<span class="pre">3))</span></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"><span class="pre">one_or_more</span></tt>, <tt class="docutils literal"><span class="pre">optional</span></tt> +and <tt class="docutils literal"><span class="pre">required</span></tt> properties.</li> +<li><tt class="docutils literal"><span class="pre">init</span></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"><span class="pre">true</span></tt> and <tt class="docutils literal"><span class="pre">false</span></tt>). List options can't have <tt class="docutils literal"><span class="pre">init</span></tt> +attribute. +Usage examples: <tt class="docutils literal"><span class="pre">(switch_option</span> <span class="pre">"foo",</span> <span class="pre">(init</span> <span class="pre">true))</span></tt>; <tt class="docutils literal"><span class="pre">(prefix_option</span> +<span class="pre">"bar",</span> <span class="pre">(init</span> <span class="pre">"baz"))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">extern</span></tt> - this option is defined in some other plugin, see <a class="reference internal" href="#extern">below</a>.</li> +</ul> +</blockquote> +</li> +</ul> +<div class="section" id="external-options"> +<span id="extern"></span><h2><a class="toc-backref" href="#id15">External options</a></h2> +<p>Sometimes, when linking several plugins together, one plugin needs to +access options defined in some other plugin. Because of the way +options are implemented, such options must be marked as +<tt class="docutils literal"><span class="pre">extern</span></tt>. This is what the <tt class="docutils literal"><span class="pre">extern</span></tt> option property is +for. Example:</p> +<pre class="literal-block"> +... +(switch_option "E", (extern)) +... +</pre> +<p>If an external option has additional attributes besides 'extern', they are +ignored. See also the section on plugin <a class="reference internal" href="#priorities">priorities</a>.</p> +</div> +</div> +<div class="section" id="conditional-evaluation"> +<span id="case"></span><h1><a class="toc-backref" href="#id16">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"><span class="pre">(case</span> <span class="pre">(test_1),</span> <span class="pre">statement_1,</span> +<span class="pre">(test_2),</span> <span class="pre">statement_2,</span> <span class="pre">...</span> <span class="pre">(test_N),</span> <span class="pre">statement_N)</span></tt>. The statements +are evaluated only if the corresponding tests evaluate to true.</p> +<p>Examples:</p> +<pre class="literal-block"> +// Edge weight calculation + +// 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)) + + +// Tool command line specification + +// Evaluates to "cmdline1" if the option "-A" is provided on the +// command line; to "cmdline2" if "-B" is provided; +// otherwise to "cmdline3". + +(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"><span class="pre">"B"</span></tt> switch is never checked when switch <tt class="docutils literal"><span class="pre">"A"</span></tt> is +enabled, and the whole expression always evaluates to <tt class="docutils literal"><span class="pre">"cmdline1"</span></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"><span class="pre">switch_on</span></tt> - Returns true if a given command-line switch is provided by +the user. Can be given a list as argument, in that case <tt class="docutils literal"><span class="pre">(switch_on</span> <span class="pre">["foo",</span> +<span class="pre">"bar",</span> <span class="pre">"baz"])</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">(and</span> <span class="pre">(switch_on</span> <span class="pre">"foo"),</span> <span class="pre">(switch_on</span> +<span class="pre">"bar"),</span> <span class="pre">(switch_on</span> <span class="pre">"baz"))</span></tt>. +Example: <tt class="docutils literal"><span class="pre">(switch_on</span> <span class="pre">"opt")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">any_switch_on</span></tt> - Given a list of switch options, returns true if any of +the switches is turned on. +Example: <tt class="docutils literal"><span class="pre">(any_switch_on</span> <span class="pre">["foo",</span> <span class="pre">"bar",</span> <span class="pre">"baz"])</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">(or</span> +<span class="pre">(switch_on</span> <span class="pre">"foo"),</span> <span class="pre">(switch_on</span> <span class="pre">"bar"),</span> <span class="pre">(switch_on</span> <span class="pre">"baz"))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">parameter_equals</span></tt> - Returns true if a command-line parameter equals +a given value. +Example: <tt class="docutils literal"><span class="pre">(parameter_equals</span> <span class="pre">"W",</span> <span class="pre">"all")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">element_in_list</span></tt> - Returns true if a command-line parameter +list contains a given value. +Example: <tt class="docutils literal"><span class="pre">(element_in_list</span> <span class="pre">"l",</span> <span class="pre">"pthread")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">input_languages_contain</span></tt> - Returns true if a given language +belongs to the current input language set. +Example: <tt class="docutils literal"><span class="pre">(input_languages_contain</span> <span class="pre">"c++")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">in_language</span></tt> - Evaluates to true if the input file language is equal to +the argument. At the moment works only with <tt class="docutils literal"><span class="pre">cmd_line</span></tt> and <tt class="docutils literal"><span class="pre">actions</span></tt> (on +non-join nodes). +Example: <tt class="docutils literal"><span class="pre">(in_language</span> <span class="pre">"c++")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">not_empty</span></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"><span class="pre">switch_on</span></tt>, can +be also given a list as argument. +Example: <tt class="docutils literal"><span class="pre">(not_empty</span> <span class="pre">"o")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">any_not_empty</span></tt> - Returns true if <tt class="docutils literal"><span class="pre">not_empty</span></tt> returns true for any of +the options in the list. +Example: <tt class="docutils literal"><span class="pre">(any_not_empty</span> <span class="pre">["foo",</span> <span class="pre">"bar",</span> <span class="pre">"baz"])</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">(or</span> +<span class="pre">(not_empty</span> <span class="pre">"foo"),</span> <span class="pre">(not_empty</span> <span class="pre">"bar"),</span> <span class="pre">(not_empty</span> <span class="pre">"baz"))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">empty</span></tt> - The opposite of <tt class="docutils literal"><span class="pre">not_empty</span></tt>. Equivalent to <tt class="docutils literal"><span class="pre">(not</span> <span class="pre">(not_empty</span> +<span class="pre">X))</span></tt>. Provided for convenience. Can be given a list as argument.</li> +<li><tt class="docutils literal"><span class="pre">any_not_empty</span></tt> - Returns true if <tt class="docutils literal"><span class="pre">not_empty</span></tt> returns true for any of +the options in the list. +Example: <tt class="docutils literal"><span class="pre">(any_empty</span> <span class="pre">["foo",</span> <span class="pre">"bar",</span> <span class="pre">"baz"])</span></tt> is equivalent to <tt class="docutils literal"><span class="pre">(not</span> <span class="pre">(and</span> +<span class="pre">(not_empty</span> <span class="pre">"foo"),</span> <span class="pre">(not_empty</span> <span class="pre">"bar"),</span> <span class="pre">(not_empty</span> <span class="pre">"baz")))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">single_input_file</span></tt> - Returns true if there was only one input file +provided on the command-line. Used without arguments: +<tt class="docutils literal"><span class="pre">(single_input_file)</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">multiple_input_files</span></tt> - Equivalent to <tt class="docutils literal"><span class="pre">(not</span> <span class="pre">(single_input_file))</span></tt> (the +case of zero input files is considered an error).</li> +<li><tt class="docutils literal"><span class="pre">default</span></tt> - Always evaluates to true. Should always be the last +test in the <tt class="docutils literal"><span class="pre">case</span></tt> expression.</li> +<li><tt class="docutils literal"><span class="pre">and</span></tt> - A standard binary logical combinator that returns true iff all of +its arguments return true. Used like this: <tt class="docutils literal"><span class="pre">(and</span> <span class="pre">(test1),</span> <span class="pre">(test2),</span> +<span class="pre">...</span> <span class="pre">(testN))</span></tt>. Nesting of <tt class="docutils literal"><span class="pre">and</span></tt> and <tt class="docutils literal"><span class="pre">or</span></tt> is allowed, but not +encouraged.</li> +<li><tt class="docutils literal"><span class="pre">or</span></tt> - A binary logical combinator that returns true iff any of its +arguments returns true. Example: <tt class="docutils literal"><span class="pre">(or</span> <span class="pre">(test1),</span> <span class="pre">(test2),</span> <span class="pre">...</span> <span class="pre">(testN))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">not</span></tt> - Standard unary logical combinator that negates its +argument. Example: <tt class="docutils literal"><span class="pre">(not</span> <span class="pre">(or</span> <span class="pre">(test1),</span> <span class="pre">(test2),</span> <span class="pre">...</span> <span class="pre">(testN)))</span></tt>.</li> +</ul> +</li> +</ul> +</div> +<div class="section" id="writing-a-tool-description"> +<h1><a class="toc-backref" href="#id17">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"><span class="pre">include/llvm/CompilerDriver/Tools.td</span></tt> file):</p> +<pre class="literal-block"> +def llvm_gcc_cpp : Tool<[ + (in_language "c++"), + (out_language "llvm-assembler"), + (output_suffix "bc"), + (cmd_line "llvm-g++ -c $INFILE -o $OUTFILE -emit-llvm"), + (sink) + ]>; +</pre> +<p>This defines a new tool called <tt class="docutils literal"><span class="pre">llvm_gcc_cpp</span></tt>, which is an alias for +<tt class="docutils literal"><span class="pre">llvm-g++</span></tt>. As you can see, a tool definition is just a list of +properties; most of them should be self-explanatory. The <tt class="docutils literal"><span class="pre">sink</span></tt> +property means that this tool should be passed all command-line +options that aren't mentioned in the option list.</p> +<p>The complete list of all currently implemented tool properties follows.</p> +<ul class="simple"> +<li>Possible tool properties:<ul> +<li><tt class="docutils literal"><span class="pre">in_language</span></tt> - input language name. Can be either a string or a +list, in case the tool supports multiple input languages.</li> +<li><tt class="docutils literal"><span class="pre">out_language</span></tt> - output language name. Multiple output languages are not +allowed.</li> +<li><tt class="docutils literal"><span class="pre">output_suffix</span></tt> - output file suffix. Can also be changed +dynamically, see documentation on actions.</li> +<li><tt class="docutils literal"><span class="pre">cmd_line</span></tt> - the actual command used to run the tool. You can +use <tt class="docutils literal"><span class="pre">$INFILE</span></tt> and <tt class="docutils literal"><span class="pre">$OUTFILE</span></tt> variables, output redirection +with <tt class="docutils literal"><span class="pre">></span></tt>, hook invocations (<tt class="docutils literal"><span class="pre">$CALL</span></tt>), environment variables +(via <tt class="docutils literal"><span class="pre">$ENV</span></tt>) and the <tt class="docutils literal"><span class="pre">case</span></tt> construct.</li> +<li><tt class="docutils literal"><span class="pre">join</span></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"><span class="pre">sink</span></tt> - all command-line options that are not handled by other +tools are passed to this tool.</li> +<li><tt class="docutils literal"><span class="pre">actions</span></tt> - A single big <tt class="docutils literal"><span class="pre">case</span></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> +</li> +</ul> +<div class="section" id="id5"> +<span id="actions"></span><h2><a class="toc-backref" href="#id18">Actions</a></h2> +<p>A tool often needs to react to command-line options, and this is +precisely what the <tt class="docutils literal"><span class="pre">actions</span></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"), + (cmd_line "llvm-gcc $INFILE -o $OUTFILE"), + (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"><span class="pre">actions</span></tt> tool property is implemented on top of the omnipresent +<tt class="docutils literal"><span class="pre">case</span></tt> expression. It associates one or more different <em>actions</em> +with given conditions - in the example, the actions are <tt class="docutils literal"><span class="pre">forward</span></tt>, +which forwards a given option unchanged, and <tt class="docutils literal"><span class="pre">append_cmd</span></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"><span class="pre">case</span></tt> +construct can also be used in the <tt class="docutils literal"><span class="pre">cmd_line</span></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"><span class="pre">append_cmd</span></tt> - Append a string to the tool invocation command. +Example: <tt class="docutils literal"><span class="pre">(case</span> <span class="pre">(switch_on</span> <span class="pre">"pthread"),</span> <span class="pre">(append_cmd</span> <span class="pre">"-lpthread"))</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">error</span></tt> - Exit with error. +Example: <tt class="docutils literal"><span class="pre">(error</span> <span class="pre">"Mixing</span> <span class="pre">-c</span> <span class="pre">and</span> <span class="pre">-S</span> <span class="pre">is</span> <span class="pre">not</span> <span class="pre">allowed!")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">warning</span></tt> - Print a warning. +Example: <tt class="docutils literal"><span class="pre">(warning</span> <span class="pre">"Specifying</span> <span class="pre">both</span> <span class="pre">-O1</span> <span class="pre">and</span> <span class="pre">-O2</span> <span class="pre">is</span> <span class="pre">meaningless!")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">forward</span></tt> - Forward the option unchanged. +Example: <tt class="docutils literal"><span class="pre">(forward</span> <span class="pre">"Wall")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">forward_as</span></tt> - Change the option's name, but forward the argument +unchanged. +Example: <tt class="docutils literal"><span class="pre">(forward_as</span> <span class="pre">"O0",</span> <span class="pre">"--disable-optimization")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">forward_value</span></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"><span class="pre">(forward_value</span> <span class="pre">"Wa,")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">forward_transformed_value</span></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"><span class="pre">forward_transformed_value</span></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> <span class="pre">(const</span> <span class="pre">std::vector<std::string>&)</span></tt>. +Example: <tt class="docutils literal"><span class="pre">(forward_transformed_value</span> <span class="pre">"m",</span> <span class="pre">"ConvertToMAttr")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">output_suffix</span></tt> - Modify the output suffix of this tool. +Example: <tt class="docutils literal"><span class="pre">(output_suffix</span> <span class="pre">"i")</span></tt>.</li> +<li><tt class="docutils literal"><span class="pre">stop_compilation</span></tt> - Stop compilation after this tool processes its +input. Used without arguments. +Example: <tt class="docutils literal"><span class="pre">(stop_compilation)</span></tt>.</li> +</ul> +</blockquote> +</li> +</ul> +</div> +</div> +<div class="section" id="language-map"> +<h1><a class="toc-backref" href="#id19">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. Since a tool can't have multiple output languages, for inner nodes of +the graph the input and output languages should match. This is enforced at +compile-time.</p> +</div> +<div class="section" id="option-preprocessor"> +<h1><a class="toc-backref" href="#id20">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"><span class="pre">OptionPreprocessor</span></tt> feature is reserved specially for these +occasions. Example (adapted from the built-in Base plugin):</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"><span class="pre">OptionPreprocessor</span></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"><span class="pre">OptionPreprocessor</span></tt> is basically a single big <tt class="docutils literal"><span class="pre">case</span></tt> expression, which is +evaluated only once right after the plugin is loaded. The only allowed actions +in <tt class="docutils literal"><span class="pre">OptionPreprocessor</span></tt> are <tt class="docutils literal"><span class="pre">error</span></tt>, <tt class="docutils literal"><span class="pre">warning</span></tt>, and two special actions: +<tt class="docutils literal"><span class="pre">unset_option</span></tt> and <tt class="docutils literal"><span class="pre">set_option</span></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"><span class="pre">set_option</span></tt>, use the +two-argument form: <tt class="docutils literal"><span class="pre">(set_option</span> <span class="pre">"parameter",</span> <span class="pre">VALUE)</span></tt>. Here, <tt class="docutils literal"><span class="pre">VALUE</span></tt> can be +either a string, a string list, or a boolean constant.</p> +<p>For convenience, <tt class="docutils literal"><span class="pre">set_option</span></tt> and <tt class="docutils literal"><span class="pre">unset_option</span></tt> also work on lists. That +is, instead of <tt class="docutils literal"><span class="pre">[(unset_option</span> <span class="pre">"A"),</span> <span class="pre">(unset_option</span> <span class="pre">"B")]</span></tt> you can use +<tt class="docutils literal"><span class="pre">(unset_option</span> <span class="pre">["A",</span> <span class="pre">"B"])</span></tt>. Obviously, <tt class="docutils literal"><span class="pre">(set_option</span> <span class="pre">["A",</span> <span class="pre">"B"])</span></tt> is valid +only if both <tt class="docutils literal"><span class="pre">A</span></tt> and <tt class="docutils literal"><span class="pre">B</span></tt> are switches.</p> +</div> +<div class="section" id="more-advanced-topics"> +<h1><a class="toc-backref" href="#id21">More advanced topics</a></h1> +<div class="section" id="hooks-and-environment-variables"> +<span id="hooks"></span><h2><a class="toc-backref" href="#id22">Hooks and environment variables</a></h2> +<p>Normally, LLVMC executes programs from the system <tt class="docutils literal"><span class="pre">PATH</span></tt>. Sometimes, +this is not sufficient: for example, we may want to specify tool paths +or names in the configuration file. This can be easily achieved via +the hooks mechanism. To write your own hooks, just add their +definitions to the <tt class="docutils literal"><span class="pre">PluginMain.cpp</span></tt> or drop a <tt class="docutils literal"><span class="pre">.cpp</span></tt> file into the +your plugin directory. Hooks should live in the <tt class="docutils literal"><span class="pre">hooks</span></tt> namespace +and have the signature <tt class="docutils literal"><span class="pre">std::string</span> <span class="pre">hooks::MyHookName</span> <span class="pre">([const</span> <span class="pre">char*</span> +<span class="pre">Arg0</span> <span class="pre">[</span> <span class="pre">const</span> <span class="pre">char*</span> <span class="pre">Arg2</span> <span class="pre">[,</span> <span class="pre">...]]])</span></tt>. They can be used from the +<tt class="docutils literal"><span class="pre">cmd_line</span></tt> tool property:</p> +<pre class="literal-block"> +(cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)") +</pre> +<p>To pass arguments to hooks, use the following syntax:</p> +<pre class="literal-block"> +(cmd_line "$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"> +(cmd_line "$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"><span class="pre">case</span></tt> expression (documented <a class="reference internal" href="#case">above</a>):</p> +<pre class="literal-block"> +(cmd_line + (case + (switch_on "E"), + "llvm-g++ -E -x c $INFILE -o $OUTFILE", + (default), + "llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm")) +</pre> +</div> +<div class="section" id="how-plugins-are-loaded"> +<span id="priorities"></span><h2><a class="toc-backref" href="#id23">How plugins are loaded</a></h2> +<p>It is possible for LLVMC plugins to depend on each other. For example, +one can create edges between nodes defined in some other plugin. To +make this work, however, that plugin should be loaded first. To +achieve this, the concept of plugin priority was introduced. By +default, every plugin has priority zero; to specify the priority +explicitly, put the following line in your plugin's TableGen file:</p> +<pre class="literal-block"> +def Priority : PluginPriority<$PRIORITY_VALUE>; +# Where PRIORITY_VALUE is some integer > 0 +</pre> +<p>Plugins are loaded in order of their (increasing) priority, starting +with 0. Therefore, the plugin with the highest priority value will be +loaded last.</p> +</div> +<div class="section" id="debugging"> +<h2><a class="toc-backref" href="#id24">Debugging</a></h2> +<p>When writing LLVMC plugins, 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>. This command 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"><span class="pre">llvmc</span></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. These checks can't +be performed at compile-time because the plugins can load code +dynamically. When invoked with <tt class="docutils literal"><span class="pre">--check-graph</span></tt>, <tt class="docutils literal"><span class="pre">llvmc</span></tt> doesn't +perform any compilation tasks and returns the number of encountered +errors as its status code.</p> +</div> +<div class="section" id="conditioning-on-the-executable-name"> +<h2><a class="toc-backref" href="#id25">Conditioning on the executable name</a></h2> +<p>For now, the executable name (the value passed to the driver in <tt class="docutils literal"><span class="pre">argv[0]</span></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; +} + +namespace hooks { + +std::string MyHook() { +//... +if (strcmp(ProgramName, "mydriver") == 0) { + //... + +} + +} // 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"><span class="pre">Base</span></tt> plugin behaves when it needs to choose the correct linker options +(think <tt class="docutils literal"><span class="pre">g++</span></tt> vs. <tt class="docutils literal"><span class="pre">gcc</span></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> + +<a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a><br /> +<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br /> + +Last modified: $Date$ +</address></div> +</div> +</div> +</body> +</html> |