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| <div class="document" id="customizing-llvmc-reference-manual"> | |
| <h1 class="title">Customizing LLVMC: Reference Manual</h1> | |
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| <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"> | |
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| alt="Valid CSS" /></a> | |
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| 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> | |
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