| <?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>. 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">zero_or_one</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">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>. Only list options can have this attribute; you can, however, use |
| the <tt class="docutils literal"><span class="pre">one_or_more</span></tt> and <tt class="docutils literal"><span class="pre">zero_or_one</span></tt> properties.</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 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" 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: $Date$ |
| </address></div> |
| </div> |
| </div> |
| </body> |
| </html> |
