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===================================
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Customizing LLVMC: Reference Manual
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===================================
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This file was automatically generated by rst2html.
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Please do not edit directly!
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The ReST source lives in the directory 'tools/llvmc/doc'.
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<div class="doc_author">
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<p>Written by <a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a></p>
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LLVMC is a generic compiler driver, designed to be customizable and
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extensible. It plays the same role for LLVM as the ``gcc`` program
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does for GCC - LLVMC's job is essentially to transform a set of input
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files into a set of targets depending on configuration rules and user
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options. What makes LLVMC different is that these transformation rules
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are completely customizable - in fact, LLVMC knows nothing about the
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specifics of transformation (even the command-line options are mostly
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not hard-coded) and regards the transformation structure as an
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abstract graph. The structure of this graph is completely determined
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by plugins, which can be either statically or dynamically linked. This
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makes it possible to easily adapt LLVMC for other purposes - for
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example, as a build tool for game resources.
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Because LLVMC employs TableGen_ as its configuration language, you
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need to be familiar with it to customize LLVMC.
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.. _TableGen: http://llvm.org/docs/TableGenFundamentals.html
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LLVMC tries hard to be as compatible with ``gcc`` as possible,
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although there are some small differences. Most of the time, however,
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you shouldn't be able to notice them::
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$ # This works as expected:
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$ llvmc -O3 -Wall hello.cpp
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One nice feature of LLVMC is that one doesn't have to distinguish between
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different compilers for different languages (think ``g++`` vs. ``gcc``) - the
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right toolchain is chosen automatically based on input language names (which
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are, in turn, determined from file extensions). If you want to force files
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ending with ".c" to compile as C++, use the ``-x`` option, just like you would
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$ # hello.c is really a C++ file
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$ llvmc -x c++ hello.c
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On the other hand, when using LLVMC as a linker to combine several C++
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object files you should provide the ``--linker`` option since it's
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impossible for LLVMC to choose the right linker in that case::
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[A lot of link-time errors skipped]
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$ llvmc --linker=c++ hello.o
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By default, LLVMC uses ``llvm-gcc`` to compile the source code. It is also
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possible to choose the ``clang`` compiler with the ``-clang`` option.
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LLVMC has some built-in options that can't be overridden in the
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configuration libraries:
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* ``-o FILE`` - Output file name.
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* ``-x LANGUAGE`` - Specify the language of the following input files
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until the next -x option.
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* ``-load PLUGIN_NAME`` - Load the specified plugin DLL. Example:
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``-load $LLVM_DIR/Release/lib/LLVMCSimple.so``.
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* ``-v`` - Enable verbose mode, i.e. print out all executed commands.
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* ``--save-temps`` - Write temporary files to the current directory and do not
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delete them on exit. This option can also take an argument: the
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``--save-temps=obj`` switch will write files into the directory specified with
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the ``-o`` option. The ``--save-temps=cwd`` and ``--save-temps`` switches are
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both synonyms for the default behaviour.
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* ``--temp-dir DIRECTORY`` - Store temporary files in the given directory. This
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directory is deleted on exit unless ``--save-temps`` is specified. If
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``--save-temps=obj`` is also specified, ``--temp-dir`` is given the
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* ``--check-graph`` - Check the compilation for common errors like mismatched
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output/input language names, multiple default edges and cycles. Because of
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plugins, these checks can't be performed at compile-time. Exit with code zero
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if no errors were found, and return the number of found errors
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otherwise. Hidden option, useful for debugging LLVMC plugins.
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* ``--view-graph`` - Show a graphical representation of the compilation graph
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and exit. Requires that you have ``dot`` and ``gv`` programs installed. Hidden
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option, useful for debugging LLVMC plugins.
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* ``--write-graph`` - Write a ``compilation-graph.dot`` file in the current
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directory with the compilation graph description in Graphviz format (identical
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to the file used by the ``--view-graph`` option). The ``-o`` option can be
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used to set the output file name. Hidden option, useful for debugging LLVMC
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* ``--help``, ``--help-hidden``, ``--version`` - These options have
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their standard meaning.
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Compiling LLVMC plugins
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=======================
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It's easiest to start working on your own LLVMC plugin by copying the
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skeleton project which lives under ``$LLVMC_DIR/plugins/Simple``::
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$ cd $LLVMC_DIR/plugins
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$ cp -r Simple MyPlugin
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Makefile PluginMain.cpp Simple.td
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As you can see, our basic plugin consists of only two files (not
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counting the build script). ``Simple.td`` contains TableGen
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description of the compilation graph; its format is documented in the
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following sections. ``PluginMain.cpp`` is just a helper file used to
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compile the auto-generated C++ code produced from TableGen source. It
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can also contain hook definitions (see `below`__).
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The first thing that you should do is to change the ``LLVMC_PLUGIN``
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variable in the ``Makefile`` to avoid conflicts (since this variable
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is used to name the resulting library)::
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LLVMC_PLUGIN=MyPlugin
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It is also a good idea to rename ``Simple.td`` to something less
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$ mv Simple.td MyPlugin.td
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To build your plugin as a dynamic library, just ``cd`` to its source
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directory and run ``make``. The resulting file will be called
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``plugin_llvmc_$(LLVMC_PLUGIN).$(DLL_EXTENSION)`` (in our case,
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``plugin_llvmc_MyPlugin.so``). This library can be then loaded in with the
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``-load`` option. Example::
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$ cd $LLVMC_DIR/plugins/Simple
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$ llvmc -load $LLVM_DIR/Release/lib/plugin_llvmc_Simple.so
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Compiling standalone LLVMC-based drivers
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========================================
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By default, the ``llvmc`` executable consists of a driver core plus several
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statically linked plugins (``Base`` and ``Clang`` at the moment). You can
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produce a standalone LLVMC-based driver executable by linking the core with your
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own plugins. The recommended way to do this is by starting with the provided
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``Skeleton`` example (``$LLVMC_DIR/example/Skeleton``)::
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$ cd $LLVMC_DIR/example/
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$ cp -r Skeleton mydriver
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If you're compiling LLVM with different source and object directories, then you
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must perform the following additional steps before running ``make``::
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# LLVMC_SRC_DIR = $LLVM_SRC_DIR/tools/llvmc/
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# LLVMC_OBJ_DIR = $LLVM_OBJ_DIR/tools/llvmc/
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$ cp $LLVMC_SRC_DIR/example/mydriver/Makefile \
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$LLVMC_OBJ_DIR/example/mydriver/
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$ cd $LLVMC_OBJ_DIR/example/mydriver
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Another way to do the same thing is by using the following command::
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$ make LLVMC_BUILTIN_PLUGINS=MyPlugin LLVMC_BASED_DRIVER_NAME=mydriver
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This works with both srcdir == objdir and srcdir != objdir, but assumes that the
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plugin source directory was placed under ``$LLVMC_DIR/plugins``.
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Sometimes, you will want a 'bare-bones' version of LLVMC that has no
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built-in plugins. It can be compiled with the following command::
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$ make LLVMC_BUILTIN_PLUGINS=""
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Customizing LLVMC: the compilation graph
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========================================
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Each TableGen configuration file should include the common
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include "llvm/CompilerDriver/Common.td"
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Internally, LLVMC stores information about possible source
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transformations in form of a graph. Nodes in this graph represent
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tools, and edges between two nodes represent a transformation path. A
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special "root" node is used to mark entry points for the
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transformations. LLVMC also assigns a weight to each edge (more on
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this later) to choose between several alternative edges.
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The definition of the compilation graph (see file
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``plugins/Base/Base.td`` for an example) is just a list of edges::
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def CompilationGraph : CompilationGraph<[
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Edge<"root", "llvm_gcc_c">,
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Edge<"root", "llvm_gcc_assembler">,
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Edge<"llvm_gcc_c", "llc">,
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Edge<"llvm_gcc_cpp", "llc">,
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OptionalEdge<"llvm_gcc_c", "opt", (case (switch_on "opt"),
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OptionalEdge<"llvm_gcc_cpp", "opt", (case (switch_on "opt"),
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OptionalEdge<"llvm_gcc_assembler", "llvm_gcc_cpp_linker",
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(case (input_languages_contain "c++"), (inc_weight),
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(or (parameter_equals "linker", "g++"),
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(parameter_equals "linker", "c++")), (inc_weight))>,
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As you can see, the edges can be either default or optional, where
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optional edges are differentiated by an additional ``case`` expression
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used to calculate the weight of this edge. Notice also that we refer
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to tools via their names (as strings). This makes it possible to add
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edges to an existing compilation graph in plugins without having to
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know about all tool definitions used in the graph.
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The default edges are assigned a weight of 1, and optional edges get a
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weight of 0 + 2*N where N is the number of tests that evaluated to
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true in the ``case`` expression. It is also possible to provide an
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integer parameter to ``inc_weight`` and ``dec_weight`` - in this case,
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the weight is increased (or decreased) by the provided value instead
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of the default 2. It is also possible to change the default weight of
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an optional edge by using the ``default`` clause of the ``case``
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When passing an input file through the graph, LLVMC picks the edge
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with the maximum weight. To avoid ambiguity, there should be only one
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default edge between two nodes (with the exception of the root node,
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which gets a special treatment - there you are allowed to specify one
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default edge *per language*).
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When multiple plugins are loaded, their compilation graphs are merged
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together. Since multiple edges that have the same end nodes are not
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allowed (i.e. the graph is not a multigraph), an edge defined in
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several plugins will be replaced by the definition from the plugin
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that was loaded last. Plugin load order can be controlled by using the
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plugin priority feature described above.
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To get a visual representation of the compilation graph (useful for
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debugging), run ``llvmc --view-graph``. You will need ``dot`` and
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``gsview`` installed for this to work properly.
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Command-line options that the plugin supports are defined by using an
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def Options : OptionList<[
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(switch_option "E", (help "Help string")),
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(alias_option "quiet", "q")
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As you can see, the option list is just a list of DAGs, where each DAG
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is an option description consisting of the option name and some
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properties. A plugin can define more than one option list (they are
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all merged together in the end), which can be handy if one wants to
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separate option groups syntactically.
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* Possible option types:
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- ``switch_option`` - a simple boolean switch without arguments, for example
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``-O2`` or ``-time``. At most one occurrence is allowed.
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- ``parameter_option`` - option that takes one argument, for example
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``-std=c99``. It is also allowed to use spaces instead of the equality
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sign: ``-std c99``. At most one occurrence is allowed.
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- ``parameter_list_option`` - same as the above, but more than one option
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occurence is allowed.
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- ``prefix_option`` - same as the parameter_option, but the option name and
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argument do not have to be separated. Example: ``-ofile``. This can be also
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specified as ``-o file``; however, ``-o=file`` will be parsed incorrectly
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(``=file`` will be interpreted as option value). At most one occurrence is
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- ``prefix_list_option`` - same as the above, but more than one occurence of
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the option is allowed; example: ``-lm -lpthread``.
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- ``alias_option`` - a special option type for creating aliases. Unlike other
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option types, aliases are not allowed to have any properties besides the
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aliased option name. Usage example: ``(alias_option "preprocess", "E")``
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* Possible option properties:
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- ``help`` - help string associated with this option. Used for ``--help``
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- ``required`` - this option must be specified exactly once (or, in case of
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the list options without the ``multi_val`` property, at least
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once). Incompatible with ``optional`` and ``one_or_more``.
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- ``optional`` - the option can be specified either zero times or exactly
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once. The default for switch options. Useful only for list options in
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conjunction with ``multi_val``. Incompatible with ``required``,
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``zero_or_more`` and ``one_or_more``.
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- ``one_or_more`` - the option must be specified at least once. Can be useful
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to allow switch options be both obligatory and be specified multiple
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times. For list options is useful only in conjunction with ``multi_val``;
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for ordinary it is synonymous with ``required``. Incompatible with
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``required``, ``optional`` and ``zero_or_more``.
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- ``zero_or_more`` - the option can be specified zero or more times. Useful
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to allow a single switch option to be specified more than
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once. Incompatible with ``required``, ``optional`` and ``one_or_more``.
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- ``hidden`` - the description of this option will not appear in
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the ``--help`` output (but will appear in the ``--help-hidden``
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- ``really_hidden`` - the option will not be mentioned in any help
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- ``comma_separated`` - Indicates that any commas specified for an option's
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value should be used to split the value up into multiple values for the
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option. This property is valid only for list options. In conjunction with
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``forward_value`` can be used to implement option forwarding in style of
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- ``multi_val n`` - this option takes *n* arguments (can be useful in some
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special cases). Usage example: ``(parameter_list_option "foo", (multi_val
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3))``; the command-line syntax is '-foo a b c'. Only list options can have
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this attribute; you can, however, use the ``one_or_more``, ``optional``
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and ``required`` properties.
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- ``init`` - this option has a default value, either a string (if it is a
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parameter), or a boolean (if it is a switch; as in C++, boolean constants
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are called ``true`` and ``false``). List options can't have ``init``
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Usage examples: ``(switch_option "foo", (init true))``; ``(prefix_option
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"bar", (init "baz"))``.
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- ``extern`` - this option is defined in some other plugin, see `below`__.
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Sometimes, when linking several plugins together, one plugin needs to
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access options defined in some other plugin. Because of the way
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options are implemented, such options must be marked as
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``extern``. This is what the ``extern`` option property is
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(switch_option "E", (extern))
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If an external option has additional attributes besides 'extern', they are
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ignored. See also the section on plugin `priorities`__.
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Conditional evaluation
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======================
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The 'case' construct is the main means by which programmability is
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achieved in LLVMC. It can be used to calculate edge weights, program
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actions and modify the shell commands to be executed. The 'case'
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expression is designed after the similarly-named construct in
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functional languages and takes the form ``(case (test_1), statement_1,
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(test_2), statement_2, ... (test_N), statement_N)``. The statements
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are evaluated only if the corresponding tests evaluate to true.
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// Edge weight calculation
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// Increases edge weight by 5 if "-A" is provided on the
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// command-line, and by 5 more if "-B" is also provided.
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(switch_on "A"), (inc_weight 5),
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(switch_on "B"), (inc_weight 5))
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// Tool command line specification
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// Evaluates to "cmdline1" if the option "-A" is provided on the
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// command line; to "cmdline2" if "-B" is provided;
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// otherwise to "cmdline3".
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(switch_on "A"), "cmdline1",
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(switch_on "B"), "cmdline2",
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(default), "cmdline3")
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Note the slight difference in 'case' expression handling in contexts
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of edge weights and command line specification - in the second example
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the value of the ``"B"`` switch is never checked when switch ``"A"`` is
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enabled, and the whole expression always evaluates to ``"cmdline1"`` in
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Case expressions can also be nested, i.e. the following is legal::
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(case (switch_on "E"), (case (switch_on "o"), ..., (default), ...)
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You should, however, try to avoid doing that because it hurts
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readability. It is usually better to split tool descriptions and/or
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use TableGen inheritance instead.
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* Possible tests are:
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- ``switch_on`` - Returns true if a given command-line switch is provided by
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the user. Can be given a list as argument, in that case ``(switch_on ["foo",
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"bar", "baz"])`` is equivalent to ``(and (switch_on "foo"), (switch_on
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"bar"), (switch_on "baz"))``.
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Example: ``(switch_on "opt")``.
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- ``any_switch_on`` - Given a list of switch options, returns true if any of
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the switches is turned on.
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Example: ``(any_switch_on ["foo", "bar", "baz"])`` is equivalent to ``(or
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(switch_on "foo"), (switch_on "bar"), (switch_on "baz"))``.
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- ``parameter_equals`` - Returns true if a command-line parameter equals
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Example: ``(parameter_equals "W", "all")``.
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- ``element_in_list`` - Returns true if a command-line parameter
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list contains a given value.
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Example: ``(element_in_list "l", "pthread")``.
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- ``input_languages_contain`` - Returns true if a given language
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belongs to the current input language set.
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Example: ``(input_languages_contain "c++")``.
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- ``in_language`` - Evaluates to true if the input file language is equal to
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the argument. At the moment works only with ``cmd_line`` and ``actions`` (on
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Example: ``(in_language "c++")``.
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- ``not_empty`` - Returns true if a given option (which should be either a
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parameter or a parameter list) is set by the user. Like ``switch_on``, can
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be also given a list as argument.
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Example: ``(not_empty "o")``.
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- ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of
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the options in the list.
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Example: ``(any_not_empty ["foo", "bar", "baz"])`` is equivalent to ``(or
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(not_empty "foo"), (not_empty "bar"), (not_empty "baz"))``.
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- ``empty`` - The opposite of ``not_empty``. Equivalent to ``(not (not_empty
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X))``. Provided for convenience. Can be given a list as argument.
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- ``any_not_empty`` - Returns true if ``not_empty`` returns true for any of
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the options in the list.
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Example: ``(any_empty ["foo", "bar", "baz"])`` is equivalent to ``(not (and
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(not_empty "foo"), (not_empty "bar"), (not_empty "baz")))``.
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- ``single_input_file`` - Returns true if there was only one input file
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provided on the command-line. Used without arguments:
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``(single_input_file)``.
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- ``multiple_input_files`` - Equivalent to ``(not (single_input_file))`` (the
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case of zero input files is considered an error).
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- ``default`` - Always evaluates to true. Should always be the last
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test in the ``case`` expression.
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- ``and`` - A standard binary logical combinator that returns true iff all of
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its arguments return true. Used like this: ``(and (test1), (test2),
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... (testN))``. Nesting of ``and`` and ``or`` is allowed, but not
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- ``or`` - A binary logical combinator that returns true iff any of its
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arguments returns true. Example: ``(or (test1), (test2), ... (testN))``.
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- ``not`` - Standard unary logical combinator that negates its
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argument. Example: ``(not (or (test1), (test2), ... (testN)))``.
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Writing a tool description
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==========================
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As was said earlier, nodes in the compilation graph represent tools,
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which are described separately. A tool definition looks like this
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(taken from the ``include/llvm/CompilerDriver/Tools.td`` file)::
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def llvm_gcc_cpp : Tool<[
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(out_language "llvm-assembler"),
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(output_suffix "bc"),
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(cmd_line "llvm-g++ -c $INFILE -o $OUTFILE -emit-llvm"),
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This defines a new tool called ``llvm_gcc_cpp``, which is an alias for
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``llvm-g++``. As you can see, a tool definition is just a list of
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properties; most of them should be self-explanatory. The ``sink``
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property means that this tool should be passed all command-line
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options that aren't mentioned in the option list.
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The complete list of all currently implemented tool properties follows.
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* Possible tool properties:
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- ``in_language`` - input language name. Can be either a string or a
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list, in case the tool supports multiple input languages.
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- ``out_language`` - output language name. Multiple output languages are not
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- ``output_suffix`` - output file suffix. Can also be changed
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dynamically, see documentation on actions.
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- ``cmd_line`` - the actual command used to run the tool. You can
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use ``$INFILE`` and ``$OUTFILE`` variables, output redirection
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with ``>``, hook invocations (``$CALL``), environment variables
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(via ``$ENV``) and the ``case`` construct.
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- ``join`` - this tool is a "join node" in the graph, i.e. it gets a
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list of input files and joins them together. Used for linkers.
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- ``sink`` - all command-line options that are not handled by other
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tools are passed to this tool.
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- ``actions`` - A single big ``case`` expression that specifies how
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this tool reacts on command-line options (described in more detail
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A tool often needs to react to command-line options, and this is
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precisely what the ``actions`` property is for. The next example
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illustrates this feature::
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def llvm_gcc_linker : Tool<[
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(in_language "object-code"),
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(out_language "executable"),
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(output_suffix "out"),
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(cmd_line "llvm-gcc $INFILE -o $OUTFILE"),
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(actions (case (not_empty "L"), (forward "L"),
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(not_empty "l"), (forward "l"),
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[(append_cmd "-dummy1"), (append_cmd "-dummy2")])
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The ``actions`` tool property is implemented on top of the omnipresent
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``case`` expression. It associates one or more different *actions*
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with given conditions - in the example, the actions are ``forward``,
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which forwards a given option unchanged, and ``append_cmd``, which
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appends a given string to the tool execution command. Multiple actions
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can be associated with a single condition by using a list of actions
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(used in the example to append some dummy options). The same ``case``
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construct can also be used in the ``cmd_line`` property to modify the
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The "join" property used in the example means that this tool behaves
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The list of all possible actions follows.
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- ``append_cmd`` - Append a string to the tool invocation command.
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Example: ``(case (switch_on "pthread"), (append_cmd "-lpthread"))``.
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- ``error`` - Exit with error.
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Example: ``(error "Mixing -c and -S is not allowed!")``.
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- ``warning`` - Print a warning.
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Example: ``(warning "Specifying both -O1 and -O2 is meaningless!")``.
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- ``forward`` - Forward the option unchanged.
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Example: ``(forward "Wall")``.
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- ``forward_as`` - Change the option's name, but forward the argument
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Example: ``(forward_as "O0", "--disable-optimization")``.
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- ``forward_value`` - Forward only option's value. Cannot be used with switch
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options (since they don't have values), but works fine with lists.
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Example: ``(forward_value "Wa,")``.
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- ``forward_transformed_value`` - As above, but applies a hook to the
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option's value before forwarding (see `below`__). When
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``forward_transformed_value`` is applied to a list
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option, the hook must have signature
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``std::string hooks::HookName (const std::vector<std::string>&)``.
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Example: ``(forward_transformed_value "m", "ConvertToMAttr")``.
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- ``output_suffix`` - Modify the output suffix of this tool.
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Example: ``(output_suffix "i")``.
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- ``stop_compilation`` - Stop compilation after this tool processes its
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input. Used without arguments.
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Example: ``(stop_compilation)``.
649
If you are adding support for a new language to LLVMC, you'll need to
650
modify the language map, which defines mappings from file extensions
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to language names. It is used to choose the proper toolchain(s) for a
652
given input file set. Language map definition looks like this::
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def LanguageMap : LanguageMap<
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[LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>,
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LangToSuffixes<"c", ["c"]>,
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For example, without those definitions the following command wouldn't work::
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llvmc: Unknown suffix: cpp
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The language map entries are needed only for the tools that are linked from the
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root node. Since a tool can't have multiple output languages, for inner nodes of
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the graph the input and output languages should match. This is enforced at
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It is sometimes useful to run error-checking code before processing the
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compilation graph. For example, if optimization options "-O1" and "-O2" are
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implemented as switches, we might want to output a warning if the user invokes
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the driver with both of these options enabled.
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The ``OptionPreprocessor`` feature is reserved specially for these
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occasions. Example (adapted from the built-in Base plugin)::
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def Preprocess : OptionPreprocessor<
683
(case (not (any_switch_on ["O0", "O1", "O2", "O3"])),
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(and (switch_on "O3"), (any_switch_on ["O0", "O1", "O2"])),
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(unset_option ["O0", "O1", "O2"]),
687
(and (switch_on "O2"), (any_switch_on ["O0", "O1"])),
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(unset_option ["O0", "O1"]),
689
(and (switch_on "O1"), (switch_on "O0")),
693
Here, ``OptionPreprocessor`` is used to unset all spurious ``-O`` options so
694
that they are not forwarded to the compiler. If no optimization options are
695
specified, ``-O2`` is enabled.
697
``OptionPreprocessor`` is basically a single big ``case`` expression, which is
698
evaluated only once right after the plugin is loaded. The only allowed actions
699
in ``OptionPreprocessor`` are ``error``, ``warning``, and two special actions:
700
``unset_option`` and ``set_option``. As their names suggest, they can be used to
701
set or unset a given option. To set an option with ``set_option``, use the
702
two-argument form: ``(set_option "parameter", VALUE)``. Here, ``VALUE`` can be
703
either a string, a string list, or a boolean constant.
705
For convenience, ``set_option`` and ``unset_option`` also work on lists. That
706
is, instead of ``[(unset_option "A"), (unset_option "B")]`` you can use
707
``(unset_option ["A", "B"])``. Obviously, ``(set_option ["A", "B"])`` is valid
708
only if both ``A`` and ``B`` are switches.
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Hooks and environment variables
717
-------------------------------
719
Normally, LLVMC executes programs from the system ``PATH``. Sometimes,
720
this is not sufficient: for example, we may want to specify tool paths
721
or names in the configuration file. This can be easily achieved via
722
the hooks mechanism. To write your own hooks, just add their
723
definitions to the ``PluginMain.cpp`` or drop a ``.cpp`` file into the
724
your plugin directory. Hooks should live in the ``hooks`` namespace
725
and have the signature ``std::string hooks::MyHookName ([const char*
726
Arg0 [ const char* Arg2 [, ...]]])``. They can be used from the
727
``cmd_line`` tool property::
729
(cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)")
731
To pass arguments to hooks, use the following syntax::
733
(cmd_line "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2")
735
It is also possible to use environment variables in the same manner::
737
(cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
739
To change the command line string based on user-provided options use
740
the ``case`` expression (documented `above`__)::
745
"llvm-g++ -E -x c $INFILE -o $OUTFILE",
747
"llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm"))
753
How plugins are loaded
754
----------------------
756
It is possible for LLVMC plugins to depend on each other. For example,
757
one can create edges between nodes defined in some other plugin. To
758
make this work, however, that plugin should be loaded first. To
759
achieve this, the concept of plugin priority was introduced. By
760
default, every plugin has priority zero; to specify the priority
761
explicitly, put the following line in your plugin's TableGen file::
763
def Priority : PluginPriority<$PRIORITY_VALUE>;
764
# Where PRIORITY_VALUE is some integer > 0
766
Plugins are loaded in order of their (increasing) priority, starting
767
with 0. Therefore, the plugin with the highest priority value will be
773
When writing LLVMC plugins, it can be useful to get a visual view of
774
the resulting compilation graph. This can be achieved via the command
775
line option ``--view-graph``. This command assumes that Graphviz_ and
776
Ghostview_ are installed. There is also a ``--write-graph`` option that
777
creates a Graphviz source file (``compilation-graph.dot``) in the
780
Another useful ``llvmc`` option is ``--check-graph``. It checks the
781
compilation graph for common errors like mismatched output/input
782
language names, multiple default edges and cycles. These checks can't
783
be performed at compile-time because the plugins can load code
784
dynamically. When invoked with ``--check-graph``, ``llvmc`` doesn't
785
perform any compilation tasks and returns the number of encountered
786
errors as its status code.
788
.. _Graphviz: http://www.graphviz.org/
789
.. _Ghostview: http://pages.cs.wisc.edu/~ghost/
791
Conditioning on the executable name
792
-----------------------------------
794
For now, the executable name (the value passed to the driver in ``argv[0]``) is
795
accessible only in the C++ code (i.e. hooks). Use the following code::
798
extern const char* ProgramName;
803
std::string MyHook() {
805
if (strcmp(ProgramName, "mydriver") == 0) {
810
} // end namespace hooks
812
In general, you're encouraged not to make the behaviour dependent on the
813
executable file name, and use command-line switches instead. See for example how
814
the ``Base`` plugin behaves when it needs to choose the correct linker options
815
(think ``g++`` vs. ``gcc``).
821
<a href="http://jigsaw.w3.org/css-validator/check/referer">
822
<img src="http://jigsaw.w3.org/css-validator/images/vcss-blue"
823
alt="Valid CSS" /></a>
824
<a href="http://validator.w3.org/check?uri=referer">
825
<img src="http://www.w3.org/Icons/valid-xhtml10-blue"
826
alt="Valid XHTML 1.0 Transitional"/></a>
828
<a href="mailto:foldr@codedgers.com">Mikhail Glushenkov</a><br />
829
<a href="http://llvm.org">LLVM Compiler Infrastructure</a><br />
831
Last modified: $Date: 2008-12-11 11:34:48 -0600 (Thu, 11 Dec 2008) $
added
removed
libclamav/c++/llvm/tools/llvmc/doc/LLVMC-Reference.rst
