<?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 0.4.1: 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"> <p class="topic-title first"><a id="contents" name="contents">Contents</a></p> <ul class="simple"> <li><a class="reference" href="#introduction" id="id4" name="id4">Introduction</a></li> <li><a class="reference" href="#compiling-with-llvmc" id="id5" name="id5">Compiling with LLVMC</a></li> <li><a class="reference" href="#predefined-options" id="id6" name="id6">Predefined options</a></li> <li><a class="reference" href="#compiling-llvmc-plugins" id="id7" name="id7">Compiling LLVMC plugins</a></li> <li><a class="reference" href="#customizing-llvmc-the-compilation-graph" id="id8" name="id8">Customizing LLVMC: the compilation graph</a></li> <li><a class="reference" href="#describing-options" id="id9" name="id9">Describing options</a><ul> <li><a class="reference" href="#external-options" id="id10" name="id10">External options</a></li> </ul> </li> <li><a class="reference" href="#conditional-evaluation" id="id11" name="id11">Conditional evaluation</a></li> <li><a class="reference" href="#writing-a-tool-description" id="id12" name="id12">Writing a tool description</a><ul> <li><a class="reference" href="#actions" id="id13" name="id13">Actions</a></li> </ul> </li> <li><a class="reference" href="#language-map" id="id14" name="id14">Language map</a></li> <li><a class="reference" href="#more-advanced-topics" id="id15" name="id15">More advanced topics</a><ul> <li><a class="reference" href="#hooks-and-environment-variables" id="id16" name="id16">Hooks and environment variables</a></li> <li><a class="reference" href="#how-plugins-are-loaded" id="id17" name="id17">How plugins are loaded</a></li> <li><a class="reference" href="#debugging" id="id18" name="id18">Debugging</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"> <h1><a class="toc-backref" href="#id4" id="introduction" name="introduction">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" href="http://llvm.cs.uiuc.edu/docs/TableGenFundamentals.html">TableGen</a> as its configuration language, you need to be familiar with it to customize LLVMC.</p> </div> <div class="section"> <h1><a class="toc-backref" href="#id5" id="compiling-with-llvmc" name="compiling-with-llvmc">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> and <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 work-in-progress <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"> <h1><a class="toc-backref" href="#id6" id="predefined-options" name="predefined-options">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">$LLVM_DIR/Release/lib/LLVMCSimple.so</span></tt>.</li> <li><tt class="docutils literal"><span class="pre">-v</span></tt> - Enable verbose mode, i.e. print out all executed commands.</li> <li><tt class="docutils literal"><span class="pre">--check-graph</span></tt> - Check the compilation for common errors like mismatched output/input language names, multiple default edges and cycles. Hidden option, useful for debugging.</li> <li><tt class="docutils literal"><span class="pre">--view-graph</span></tt> - Show a graphical representation of the compilation graph. Requires that you have <tt class="docutils literal"><span class="pre">dot</span></tt> and <tt class="docutils literal"><span class="pre">gv</span></tt> programs installed. Hidden option, useful for debugging.</li> <li><tt class="docutils literal"><span class="pre">--write-graph</span></tt> - Write a <tt class="docutils literal"><span class="pre">compilation-graph.dot</span></tt> file in the current directory with the compilation graph description in the Graphviz format. Hidden option, useful for debugging.</li> <li><tt class="docutils literal"><span class="pre">--save-temps</span></tt> - Write temporary files to the current directory and do not delete them on exit. Hidden option, useful for debugging.</li> <li><tt class="docutils literal"><span class="pre">--help</span></tt>, <tt class="docutils literal"><span class="pre">--help-hidden</span></tt>, <tt class="docutils literal"><span class="pre">--version</span></tt> - These options have their standard meaning.</li> </ul> </div> <div class="section"> <h1><a class="toc-backref" href="#id7" id="compiling-llvmc-plugins" name="compiling-llvmc-plugins">Compiling LLVMC plugins</a></h1> <p>It's easiest to start working on your own LLVMC plugin by copying the skeleton project which lives under <tt class="docutils literal"><span class="pre">$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" 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>Note that the plugin source directory must be placed under <tt class="docutils literal"><span class="pre">$LLVMC_DIR/plugins</span></tt> to make use of the existing build infrastructure. To build a version of the LLVMC executable called <tt class="docutils literal"><span class="pre">mydriver</span></tt> with your plugin compiled in, use the following command:</p> <pre class="literal-block"> $ cd $LLVMC_DIR $ make BUILTIN_PLUGINS=MyPlugin DRIVER_NAME=mydriver </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">LLVMC$(LLVMC_PLUGIN).$(DLL_EXTENSION)</span></tt> (in our case, <tt class="docutils literal"><span class="pre">LLVMCMyPlugin.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/LLVMCSimple.so </pre> <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 BUILTIN_PLUGINS="" </pre> </div> <div class="section"> <h1><a class="toc-backref" href="#id8" id="customizing-llvmc-the-compilation-graph" name="customizing-llvmc-the-compilation-graph">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"> <h1><a class="toc-backref" href="#id9" id="describing-options" name="describing-options">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>.</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>.</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).</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 is obligatory.</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">extern</span></tt> - this option is defined in some other plugin, see below.</li> </ul> </blockquote> </li> </ul> <div class="section"> <h2><a class="toc-backref" href="#id10" id="external-options" name="external-options">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>See also the section on plugin <a class="reference" href="#priorities">priorities</a>.</p> </div> </div> <div class="section"> <h1><a class="toc-backref" href="#id11" id="conditional-evaluation" name="conditional-evaluation"><span id="case"></span>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. 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">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">(parameter_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 equals 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. 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">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.</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 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> - Another logical combinator that returns true only if any one 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> </ul> </li> </ul> </div> <div class="section"> <h1><a class="toc-backref" href="#id12" id="writing-a-tool-description" name="writing-a-tool-description">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 $OUTFILE -emit-llvm"), (sink) ]>; </pre> <p>This defines a new tool called <tt class="docutils literal"><span class="pre">llvm_gcc_cpp</span></tt>, which is an alias for <tt class="docutils literal"><span class="pre">llvm-g++</span></tt>. As you can see, a tool definition is just a list of properties; most of them should be self-explanatory. The <tt class="docutils literal"><span class="pre">sink</span></tt> property means that this tool should be passed all command-line options that aren't mentioned in the option list.</p> <p>The complete list of all currently implemented tool properties follows.</p> <ul class="simple"> <li>Possible tool properties:<ul> <li><tt class="docutils literal"><span class="pre">in_language</span></tt> - input language name. Can be either a string or a list, in case the tool supports multiple input languages.</li> <li><tt class="docutils literal"><span class="pre">out_language</span></tt> - output language name. Tools are not allowed to have multiple output languages.</li> <li><tt class="docutils literal"><span class="pre">output_suffix</span></tt> - output file suffix. Can also be changed dynamically, see documentation on actions.</li> <li><tt class="docutils literal"><span class="pre">cmd_line</span></tt> - the actual command used to run the tool. You can use <tt class="docutils literal"><span class="pre">$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 below).</li> </ul> </li> </ul> <div class="section"> <h2><a class="toc-backref" href="#id13" id="actions" name="actions">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> <span class="pre">-</span> <span class="pre">exit</span> <span class="pre">with</span> <span class="pre">error.</span> <span class="pre">Example:</span> <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">forward</span></tt> - forward an 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 name of an option, 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">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.</li> <li><tt class="docutils literal"><span class="pre">unpack_values</span></tt> - used for for splitting and forwarding comma-separated lists of options, e.g. <tt class="docutils literal"><span class="pre">-Wa,-foo=bar,-baz</span></tt> is converted to <tt class="docutils literal"><span class="pre">-foo=bar</span> <span class="pre">-baz</span></tt> and appended to the tool invocation command. Example: <tt class="docutils literal"><span class="pre">(unpack_values</span> <span class="pre">"Wa,")</span></tt>.</li> </ul> </blockquote> </li> </ul> </div> </div> <div class="section"> <h1><a class="toc-backref" href="#id14" id="language-map" name="language-map">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 should be added only for tools that are linked with the root node. Since tools are not allowed to have multiple output languages, for nodes "inside" the graph the input and output languages should match. This is enforced at compile-time.</p> </div> <div class="section"> <h1><a class="toc-backref" href="#id15" id="more-advanced-topics" name="more-advanced-topics">More advanced topics</a></h1> <div class="section"> <h2><a class="toc-backref" href="#id16" id="hooks-and-environment-variables" name="hooks-and-environment-variables"><span id="hooks"></span>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 names in the configuration file. This can be achieved via the mechanism of hooks - 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 <tt class="docutils literal"><span class="pre">$LLVMC_DIR/driver</span></tt> directory. Hooks should live in the <tt class="docutils literal"><span class="pre">hooks</span></tt> namespace and have the signature <tt class="docutils literal"><span class="pre">std::string</span> <span class="pre">hooks::MyHookName</span> <span class="pre">(void)</span></tt>. They can be used from the <tt class="docutils literal"><span class="pre">cmd_line</span></tt> tool property:</p> <pre class="literal-block"> (cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)") </pre> <p>It is also possible to use environment variables in the same manner:</p> <pre class="literal-block"> (cmd_line "$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" 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 $OUTFILE -emit-llvm")) </pre> </div> <div class="section"> <h2><a class="toc-backref" href="#id17" id="how-plugins-are-loaded" name="how-plugins-are-loaded"><span id="priorities"></span>How plugins are loaded</a></h2> <p>It is possible for LLVMC plugins to depend on each other. For example, one can create edges between nodes defined in some other plugin. To make this work, however, that plugin should be loaded first. To achieve this, the concept of plugin priority was introduced. By default, every plugin has priority zero; to specify the priority explicitly, put the following line in your plugin's TableGen file:</p> <pre class="literal-block"> def Priority : PluginPriority<$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"> <h2><a class="toc-backref" href="#id18" id="debugging" name="debugging">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" href="http://www.graphviz.org/">Graphviz</a> and <a class="reference" href="http://pages.cs.wisc.edu/~ghost/">Ghostview</a> are installed. There is also a <tt class="docutils literal"><span class="pre">--dump-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> <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: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $ </address></div> </div> </div> </body> </html>