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Remove all references to plugins from the LLVMC docs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130090 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Mikhail Glushenkov
parent
685501836b
commit
834b93b51d
@ -18,17 +18,16 @@ Introduction
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============
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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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extensible. It plays the same role for LLVM as the ``gcc`` program does for
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GCC - LLVMC's job is essentially to transform a set of input files into a set of
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targets depending on configuration rules and user options. What makes LLVMC
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different is that these transformation rules are completely customizable - in
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fact, LLVMC knows nothing about the specifics of transformation (even the
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command-line options are mostly not hard-coded) and regards the transformation
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structure as an abstract graph. The structure of this graph is described in
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high-level TableGen code, from which an efficient C++ representation is
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automatically derived. This makes it possible to adapt LLVMC for other
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purposes - for 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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@ -36,8 +35,8 @@ need to be familiar with it to customize LLVMC.
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.. _TableGen: http://llvm.org/docs/TableGenFundamentals.html
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Compiling with LLVMC
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====================
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Compiling with ``llvmc``
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========================
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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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@ -78,17 +77,13 @@ possible to choose the ``clang`` compiler with the ``-clang`` option.
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Predefined options
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==================
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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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LLVMC has some built-in options that can't be overridden in the TableGen code:
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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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@ -103,124 +98,90 @@ configuration libraries:
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precedence.
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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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output/input language names, multiple default edges and cycles. Exit with code
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zero if no errors were found, and return the number of found errors
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otherwise. Hidden option, useful for debugging.
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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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option, useful for debugging.
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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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plugins.
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used to set the output file name. Hidden option, useful for debugging.
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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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Compiling LLVMC-based drivers
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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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It's easiest to start working on your own LLVMC driver by copying the skeleton
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project which lives under ``$LLVMC_DIR/examples/Skeleton``::
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$ cd $LLVMC_DIR/plugins
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$ cp -r Simple MyPlugin
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$ cd MyPlugin
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$ cd $LLVMC_DIR/examples
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$ cp -r Skeleton MyDriver
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$ cd MyDriver
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$ ls
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Makefile PluginMain.cpp Simple.td
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AutoGenerated.td Hooks.cpp Main.cpp Makefile
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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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As you can see, our basic driver consists of only three files (not counting the
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build script). ``AutoGenerated.td`` contains TableGen description of the
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compilation graph; its format is documented in the following
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sections. ``Hooks.cpp`` is an empty file that should be used for hook
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definitions (see `below`__). ``Main.cpp`` is just a helper used to compile the
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auto-generated C++ code produced from TableGen source.
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__ hooks_
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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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The first thing that you should do is to change the ``LLVMC_BASED_DRIVER``
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variable in the ``Makefile``::
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LLVMC_PLUGIN=MyPlugin
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LLVMC_BASED_DRIVER=MyDriver
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It is also a good idea to rename ``Simple.td`` to something less
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generic::
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It can also be a good idea to put your TableGen code into a file with a less
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generic name::
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$ mv Simple.td MyPlugin.td
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$ touch MyDriver.td
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$ vim AutoGenerated.td
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[...]
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include "MyDriver.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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If you have more than one TableGen source file, they all should be included from
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``AutoGenerated.td``, since this file is used by the build system to generate
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C++ code.
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$ cd $LLVMC_DIR/plugins/Simple
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$ make
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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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$ cd mydriver
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$ vim Makefile
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[...]
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$ make
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To build your driver, just ``cd`` to its source directory and run ``make``. The
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resulting executable will be put into ``$LLVM_OBJ_DIR/$(BuildMode)/bin``.
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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 $LLVMC_OBJ_DIR/example/mydriver
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$ mkdir $LLVMC_OBJ_DIR/examples/MyDriver/
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$ cp $LLVMC_SRC_DIR/examples/MyDriver/Makefile \
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$LLVMC_OBJ_DIR/examples/MyDriver/
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$ cd $LLVMC_OBJ_DIR/examples/MyDriver
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$ make
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Another way to do the same thing is by using the following command::
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$ cd $LLVMC_DIR
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$ 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 ``$LLVMC_DIR/plugins``.
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Sometimes, you will want a 'bare-bones' version of LLVMC that has no
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built-in plugins. It can be compiled with the following command::
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$ cd $LLVMC_DIR
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$ 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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definitions::
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Each TableGen configuration file should include the common definitions::
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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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Internally, LLVMC stores information about possible source transformations in
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form of a graph. Nodes in this graph represent tools, and edges between two
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nodes represent a transformation path. A special "root" node is used to mark
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entry points for the transformations. LLVMC also assigns a weight to each edge
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(more on 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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The definition of the compilation graph (see file ``llvmc/src/Base.td`` for an
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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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@ -245,43 +206,37 @@ The definition of the compilation graph (see file
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]>;
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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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As you can see, the edges can be either default or optional, where optional
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edges are differentiated by an additional ``case`` expression used to calculate
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the weight of this edge. Notice also that we refer to tools via their names (as
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strings). This makes it possible to add edges to an existing compilation graph
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without having to 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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The default edges are assigned a weight of 1, and optional edges get a weight of
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0 + 2*N where N is the number of tests that evaluated to true in the ``case``
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expression. It is also possible to provide an integer parameter to
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``inc_weight`` and ``dec_weight`` - in this case, the weight is increased (or
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decreased) by the provided value instead of the default 2. Default weight of an
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optional edge can be changed by using the ``default`` clause of the ``case``
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construct.
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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 passing an input file through the graph, LLVMC picks the edge with the
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maximum weight. To avoid ambiguity, there should be only one default edge
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between two nodes (with the exception of the root node, which gets a special
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treatment - there you are allowed to specify one 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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When multiple compilation graphs are defined, they are merged together. Multiple
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edges with the same end nodes are not allowed (i.e. the graph is not a
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multigraph), and will lead to a compile-time error.
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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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To get a visual representation of the compilation graph (useful for debugging),
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run ``llvmc --view-graph``. You will need ``dot`` and ``gsview`` installed for
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this to work properly.
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Describing options
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==================
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Command-line options that the plugin supports are defined by using an
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Command-line options supported by the driver are defined by using an
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``OptionList``::
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def Options : OptionList<[
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@ -290,11 +245,10 @@ Command-line options that the plugin supports are defined by using an
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...
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]>;
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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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As you can see, the option list is just a list of DAGs, where each DAG is an
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option description consisting of the option name and some properties. More than
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one option list can be defined (they are all merged together in the end), which
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can be handy if one wants to separate option groups syntactically.
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* Possible option types:
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@ -380,42 +334,17 @@ separate option groups syntactically.
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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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__ extern_
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.. _extern:
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External options
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----------------
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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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for. Example::
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...
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(switch_option "E", (extern))
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...
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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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__ priorities_
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.. _case:
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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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The 'case' construct is the main means by which programmability is achieved in
|
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LLVMC. It can be used to calculate edge weights, program actions and modify the
|
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shell commands to be executed. The 'case' expression is designed after the
|
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similarly-named construct in functional languages and takes the form ``(case
|
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(test_1), statement_1, (test_2), statement_2, ... (test_N), statement_N)``. The
|
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statements are evaluated only if the corresponding tests evaluate to true.
|
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Examples::
|
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@ -439,20 +368,19 @@ Examples::
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(switch_on "B"), "cmdline2",
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(default), "cmdline3")
|
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|
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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 ``"B"`` switch is never checked when switch ``"A"`` is
|
||||
enabled, and the whole expression always evaluates to ``"cmdline1"`` in
|
||||
that case.
|
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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
|
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``"B"`` switch is never checked when switch ``"A"`` is enabled, and the whole
|
||||
expression always evaluates to ``"cmdline1"`` in that case.
|
||||
|
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Case expressions can also be nested, i.e. the following is legal::
|
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|
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(case (switch_on "E"), (case (switch_on "o"), ..., (default), ...)
|
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(default), ...)
|
||||
|
||||
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.
|
||||
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.
|
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|
||||
* Possible tests are:
|
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|
||||
@ -526,72 +454,75 @@ use TableGen inheritance instead.
|
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Example: ``(not (or (test1), (test2), ... (testN)))``.
|
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|
||||
|
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|
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Writing a tool description
|
||||
==========================
|
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|
||||
As was said earlier, nodes in the compilation graph represent tools,
|
||||
which are described separately. A tool definition looks like this
|
||||
(taken from the ``include/llvm/CompilerDriver/Tools.td`` file)::
|
||||
As was said earlier, nodes in the compilation graph represent tools, which are
|
||||
described separately. A tool definition looks like this (taken from the
|
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``llvmc/src/Base.td`` file)::
|
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|
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def llvm_gcc_cpp : Tool<[
|
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(in_language "c++"),
|
||||
(out_language "llvm-assembler"),
|
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(output_suffix "bc"),
|
||||
(cmd_line "llvm-g++ -c $INFILE -o $OUTFILE -emit-llvm"),
|
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(command "llvm-g++ -c -emit-llvm"),
|
||||
(sink)
|
||||
]>;
|
||||
|
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This defines a new tool called ``llvm_gcc_cpp``, which is an alias for
|
||||
``llvm-g++``. As you can see, a tool definition is just a list of
|
||||
properties; most of them should be self-explanatory. The ``sink``
|
||||
property means that this tool should be passed all command-line
|
||||
options that aren't mentioned in the option list.
|
||||
``llvm-g++``. As you can see, a tool definition is just a list of properties;
|
||||
most of them should be self-explanatory. The ``sink`` property means that this
|
||||
tool should be passed all command-line options that aren't mentioned in the
|
||||
option list.
|
||||
|
||||
The complete list of all currently implemented tool properties follows.
|
||||
|
||||
* Possible tool properties:
|
||||
|
||||
- ``in_language`` - input language name. Can be given multiple arguments, in
|
||||
case the tool supports multiple input languages.
|
||||
case the tool supports multiple input languages. Used for typechecking and
|
||||
mapping file extensions to tools.
|
||||
|
||||
- ``out_language`` - output language name. Multiple output languages are
|
||||
allowed.
|
||||
allowed. Used for typechecking the compilation graph.
|
||||
|
||||
- ``output_suffix`` - output file suffix. Can also be changed
|
||||
dynamically, see documentation on actions.
|
||||
|
||||
- ``cmd_line`` - the actual command used to run the tool. You can
|
||||
use ``$INFILE`` and ``$OUTFILE`` variables, output redirection
|
||||
with ``>``, hook invocations (``$CALL``), environment variables
|
||||
(via ``$ENV``) and the ``case`` construct.
|
||||
|
||||
- ``join`` - this tool is a "join node" in the graph, i.e. it gets a
|
||||
list of input files and joins them together. Used for linkers.
|
||||
|
||||
- ``sink`` - all command-line options that are not handled by other
|
||||
tools are passed to this tool.
|
||||
|
||||
- ``actions`` - A single big ``case`` expression that specifies how
|
||||
this tool reacts on command-line options (described in more detail
|
||||
`below`__).
|
||||
- ``output_suffix`` - output file suffix. Can also be changed dynamically, see
|
||||
documentation on `actions`__.
|
||||
|
||||
__ actions_
|
||||
|
||||
- ``command`` - the actual command used to run the tool. You can use output
|
||||
redirection with ``>``, hook invocations (``$CALL``), environment variables
|
||||
(via ``$ENV``) and the ``case`` construct.
|
||||
|
||||
- ``join`` - 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.
|
||||
|
||||
- ``sink`` - all command-line options that are not handled by other tools are
|
||||
passed to this tool.
|
||||
|
||||
- ``actions`` - A single big ``case`` expression that specifies how this tool
|
||||
reacts on command-line options (described in more detail `below`__).
|
||||
|
||||
__ actions_
|
||||
|
||||
- ``out_file_option``, ``in_file_option`` - Options appended to the
|
||||
``command`` string to designate output and input files. Default values are
|
||||
``"-o"`` and ``""``, respectively.
|
||||
|
||||
.. _actions:
|
||||
|
||||
Actions
|
||||
-------
|
||||
|
||||
A tool often needs to react to command-line options, and this is
|
||||
precisely what the ``actions`` property is for. The next example
|
||||
illustrates this feature::
|
||||
A tool often needs to react to command-line options, and this is precisely what
|
||||
the ``actions`` property is for. The next example illustrates this feature::
|
||||
|
||||
def llvm_gcc_linker : Tool<[
|
||||
(in_language "object-code"),
|
||||
(out_language "executable"),
|
||||
(output_suffix "out"),
|
||||
(cmd_line "llvm-gcc $INFILE -o $OUTFILE"),
|
||||
(command "llvm-gcc"),
|
||||
(join),
|
||||
(actions (case (not_empty "L"), (forward "L"),
|
||||
(not_empty "l"), (forward "l"),
|
||||
@ -599,18 +530,17 @@ illustrates this feature::
|
||||
[(append_cmd "-dummy1"), (append_cmd "-dummy2")])
|
||||
]>;
|
||||
|
||||
The ``actions`` tool property is implemented on top of the omnipresent
|
||||
``case`` expression. It associates one or more different *actions*
|
||||
with given conditions - in the example, the actions are ``forward``,
|
||||
which forwards a given option unchanged, and ``append_cmd``, 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 ``case``
|
||||
construct can also be used in the ``cmd_line`` property to modify the
|
||||
tool command line.
|
||||
The ``actions`` tool property is implemented on top of the omnipresent ``case``
|
||||
expression. It associates one or more different *actions* with given
|
||||
conditions - in the example, the actions are ``forward``, which forwards a given
|
||||
option unchanged, and ``append_cmd``, 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 ``case`` construct can also be used in the ``cmd_line`` property to modify
|
||||
the tool command line.
|
||||
|
||||
The "join" property used in the example means that this tool behaves
|
||||
like a linker.
|
||||
The "join" property used in the example means that this tool behaves like a
|
||||
linker.
|
||||
|
||||
The list of all possible actions follows.
|
||||
|
||||
@ -656,10 +586,10 @@ The list of all possible actions follows.
|
||||
Language map
|
||||
============
|
||||
|
||||
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::
|
||||
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::
|
||||
|
||||
def LanguageMap : LanguageMap<
|
||||
[LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>,
|
||||
@ -673,9 +603,7 @@ For example, without those definitions the following command wouldn't work::
|
||||
llvmc: Unknown suffix: cpp
|
||||
|
||||
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.
|
||||
root node. A tool can have multiple output languages.
|
||||
|
||||
Option preprocessor
|
||||
===================
|
||||
@ -686,7 +614,7 @@ implemented as switches, we might want to output a warning if the user invokes
|
||||
the driver with both of these options enabled.
|
||||
|
||||
The ``OptionPreprocessor`` feature is reserved specially for these
|
||||
occasions. Example (adapted from the built-in Base plugin)::
|
||||
occasions. Example (adapted from ``llvm/src/Base.td.in``)::
|
||||
|
||||
|
||||
def Preprocess : OptionPreprocessor<
|
||||
@ -705,7 +633,7 @@ that they are not forwarded to the compiler. If no optimization options are
|
||||
specified, ``-O2`` is enabled.
|
||||
|
||||
``OptionPreprocessor`` is basically a single big ``case`` expression, which is
|
||||
evaluated only once right after the plugin is loaded. The only allowed actions
|
||||
evaluated only once right after the driver is started. The only allowed actions
|
||||
in ``OptionPreprocessor`` are ``error``, ``warning``, and two special actions:
|
||||
``unset_option`` and ``set_option``. As their names suggest, they can be used to
|
||||
set or unset a given option. To set an option with ``set_option``, use the
|
||||
@ -726,30 +654,28 @@ More advanced topics
|
||||
Hooks and environment variables
|
||||
-------------------------------
|
||||
|
||||
Normally, LLVMC executes programs from the system ``PATH``. 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 ``PluginMain.cpp`` or drop a ``.cpp`` file into the
|
||||
your plugin directory. Hooks should live in the ``hooks`` namespace
|
||||
and have the signature ``std::string hooks::MyHookName ([const char*
|
||||
Arg0 [ const char* Arg2 [, ...]]])``. They can be used from the
|
||||
``cmd_line`` tool property::
|
||||
Normally, LLVMC searches for programs in the system ``PATH``. Sometimes, this is
|
||||
not sufficient: for example, we may want to specify tool paths or names in the
|
||||
configuration file. This can be achieved via the hooks mechanism. To write your
|
||||
own hooks, add their definitions to the ``Hooks.cpp`` or drop a ``.cpp`` file
|
||||
into your driver directory. Hooks should live in the ``hooks`` namespace and
|
||||
have the signature ``std::string hooks::MyHookName ([const char* Arg0 [ const
|
||||
char* Arg2 [, ...]]])``. They can be used from the ``command`` tool property::
|
||||
|
||||
(cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)")
|
||||
(command "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)")
|
||||
|
||||
To pass arguments to hooks, use the following syntax::
|
||||
|
||||
(cmd_line "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2")
|
||||
(command "$CALL(MyHook, 'Arg1', 'Arg2', 'Arg # 3')/path/to/file -o1 -o2")
|
||||
|
||||
It is also possible to use environment variables in the same manner::
|
||||
|
||||
(cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
|
||||
(command "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
|
||||
|
||||
To change the command line string based on user-provided options use
|
||||
the ``case`` expression (documented `above`__)::
|
||||
|
||||
(cmd_line
|
||||
(command
|
||||
(case
|
||||
(switch_on "E"),
|
||||
"llvm-g++ -E -x c $INFILE -o $OUTFILE",
|
||||
@ -758,42 +684,21 @@ the ``case`` expression (documented `above`__)::
|
||||
|
||||
__ case_
|
||||
|
||||
.. _priorities:
|
||||
|
||||
How plugins are loaded
|
||||
----------------------
|
||||
|
||||
It is possible for LLVMC plugins to depend on each other. For example,
|
||||
one can create edges between nodes defined in some other plugin. To
|
||||
make this work, however, that plugin should be loaded first. To
|
||||
achieve this, the concept of plugin priority was introduced. By
|
||||
default, every plugin has priority zero; to specify the priority
|
||||
explicitly, put the following line in your plugin's TableGen file::
|
||||
|
||||
def Priority : PluginPriority<$PRIORITY_VALUE>;
|
||||
# Where PRIORITY_VALUE is some integer > 0
|
||||
|
||||
Plugins are loaded in order of their (increasing) priority, starting
|
||||
with 0. Therefore, the plugin with the highest priority value will be
|
||||
loaded last.
|
||||
|
||||
Debugging
|
||||
---------
|
||||
|
||||
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 ``--view-graph``. This command assumes that Graphviz_ and
|
||||
Ghostview_ are installed. There is also a ``--write-graph`` option that
|
||||
creates a Graphviz source file (``compilation-graph.dot``) in the
|
||||
current directory.
|
||||
When writing LLVMC-based drivers, it can be useful to get a visual view of the
|
||||
resulting compilation graph. This can be achieved via the command line option
|
||||
``--view-graph`` (which assumes that Graphviz_ and Ghostview_ are
|
||||
installed). There is also a ``--write-graph`` option that creates a Graphviz
|
||||
source file (``compilation-graph.dot``) in the current directory.
|
||||
|
||||
Another useful ``llvmc`` option is ``--check-graph``. 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 ``--check-graph``, ``llvmc`` doesn't
|
||||
perform any compilation tasks and returns the number of encountered
|
||||
errors as its status code.
|
||||
Another useful ``llvmc`` option is ``--check-graph``. It checks the compilation
|
||||
graph for common errors like mismatched output/input language names, multiple
|
||||
default edges and cycles. When invoked with ``--check-graph``, ``llvmc`` doesn't
|
||||
perform any compilation tasks and returns the number of encountered errors as
|
||||
its status code. In the future, these checks will be performed at compile-time
|
||||
and this option will disappear.
|
||||
|
||||
.. _Graphviz: http://www.graphviz.org/
|
||||
.. _Ghostview: http://pages.cs.wisc.edu/~ghost/
|
||||
@ -821,7 +726,7 @@ accessible only in the C++ code (i.e. hooks). Use the following code::
|
||||
|
||||
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 ``Base`` plugin behaves when it needs to choose the correct linker options
|
||||
the ``llvmc`` program behaves when it needs to choose the correct linker options
|
||||
(think ``g++`` vs. ``gcc``).
|
||||
|
||||
.. raw:: html
|
||||
|
||||
@ -17,59 +17,54 @@ Tutorial - Using LLVMC
|
||||
Introduction
|
||||
============
|
||||
|
||||
LLVMC is a generic compiler driver, which plays the same role for LLVM
|
||||
as the ``gcc`` program does for GCC - the difference being that LLVMC
|
||||
is designed to be more adaptable and easier to customize. Most of
|
||||
LLVMC functionality is implemented via plugins, which can be loaded
|
||||
dynamically or compiled in. This tutorial describes the basic usage
|
||||
and configuration of LLVMC.
|
||||
LLVMC is a generic compiler driver, which plays the same role for LLVM as the
|
||||
``gcc`` program does for GCC - the difference being that LLVMC is designed to be
|
||||
more adaptable and easier to customize. Most of LLVMC functionality is
|
||||
implemented via high-level TableGen code, from which a corresponding C++ source
|
||||
file is automatically generated. This tutorial describes the basic usage and
|
||||
configuration of LLVMC.
|
||||
|
||||
|
||||
Compiling with LLVMC
|
||||
====================
|
||||
Using the ``llvmc`` program
|
||||
===========================
|
||||
|
||||
In general, LLVMC tries to be command-line compatible with ``gcc`` as
|
||||
much as possible, so most of the familiar options work::
|
||||
In general, ``llvmc`` tries to be command-line compatible with ``gcc`` as much
|
||||
as possible, so most of the familiar options work::
|
||||
|
||||
$ llvmc -O3 -Wall hello.cpp
|
||||
$ ./a.out
|
||||
hello
|
||||
|
||||
This will invoke ``llvm-g++`` under the hood (you can see which
|
||||
commands are executed by using the ``-v`` option). For further help on
|
||||
command-line LLVMC usage, refer to the ``llvmc --help`` output.
|
||||
This will invoke ``llvm-g++`` under the hood (you can see which commands are
|
||||
executed by using the ``-v`` option). For further help on command-line LLVMC
|
||||
usage, refer to the ``llvmc --help`` output.
|
||||
|
||||
|
||||
Using LLVMC to generate toolchain drivers
|
||||
=========================================
|
||||
|
||||
LLVMC plugins are written mostly using TableGen_, so you need to
|
||||
be familiar with it to get anything done.
|
||||
LLVMC-based drivers are written mostly using TableGen_, so you need to be
|
||||
familiar with it to get anything done.
|
||||
|
||||
.. _TableGen: http://llvm.org/docs/TableGenFundamentals.html
|
||||
|
||||
Start by compiling ``example/Simple``, which is a primitive wrapper for
|
||||
``gcc``::
|
||||
|
||||
$ cd $LLVM_DIR/tools/llvmc
|
||||
$ cp -r example/Simple plugins/Simple
|
||||
|
||||
# NB: A less verbose way to compile standalone LLVMC-based drivers is
|
||||
# described in the reference manual.
|
||||
|
||||
$ make LLVMC_BASED_DRIVER_NAME=mygcc LLVMC_BUILTIN_PLUGINS=Simple
|
||||
$ cd $LLVM_OBJ_DIR/tools/examples/Simple
|
||||
$ make
|
||||
$ cat > hello.c
|
||||
[...]
|
||||
$ mygcc hello.c
|
||||
#include <stdio.h>
|
||||
int main() { printf("Hello\n"); }
|
||||
$ $LLVM_BIN_DIR/Simple -v hello.c
|
||||
gcc hello.c -o hello.out
|
||||
$ ./hello.out
|
||||
Hello
|
||||
|
||||
Here we link our plugin with the LLVMC core statically to form an executable
|
||||
file called ``mygcc``. It is also possible to build our plugin as a dynamic
|
||||
library to be loaded by the ``llvmc`` executable (or any other LLVMC-based
|
||||
standalone driver); this is described in the reference manual.
|
||||
|
||||
Contents of the file ``Simple.td`` look like this::
|
||||
We have thus produced a simple driver called, appropriately, ``Simple``, from
|
||||
the input TableGen file ``Simple.td``. The ``llvmc`` program itself is generated
|
||||
using a similar process (see ``llvmc/src``). Contents of the file ``Simple.td``
|
||||
look like this::
|
||||
|
||||
// Include common definitions
|
||||
include "llvm/CompilerDriver/Common.td"
|
||||
@ -79,37 +74,40 @@ Contents of the file ``Simple.td`` look like this::
|
||||
[(in_language "c"),
|
||||
(out_language "executable"),
|
||||
(output_suffix "out"),
|
||||
(cmd_line "gcc $INFILE -o $OUTFILE"),
|
||||
(sink)
|
||||
(command "gcc"),
|
||||
(sink),
|
||||
|
||||
// -o is what is used by default, out_file_option here is included for
|
||||
// instructive purposes.
|
||||
(out_file_option "-o")
|
||||
]>;
|
||||
|
||||
// Language map
|
||||
def LanguageMap : LanguageMap<[LangToSuffixes<"c", ["c"]>]>;
|
||||
def LanguageMap : LanguageMap<[(lang_to_suffixes "c", "c")]>;
|
||||
|
||||
// Compilation graph
|
||||
def CompilationGraph : CompilationGraph<[Edge<"root", "gcc">]>;
|
||||
def CompilationGraph : CompilationGraph<[(edge "root", "gcc")]>;
|
||||
|
||||
As you can see, this file consists of three parts: tool descriptions,
|
||||
language map, and the compilation graph definition.
|
||||
As you can see, this file consists of three parts: tool descriptions, language
|
||||
map, and the compilation graph definition.
|
||||
|
||||
At the heart of LLVMC is the idea of a compilation graph: vertices in
|
||||
this graph are tools, and edges represent a transformation path
|
||||
between two tools (for example, assembly source produced by the
|
||||
compiler can be transformed into executable code by an assembler). The
|
||||
compilation graph is basically a list of edges; a special node named
|
||||
``root`` is used to mark graph entry points.
|
||||
At the heart of LLVMC is the idea of a compilation graph: vertices in this graph
|
||||
are tools, and edges represent a transformation path between two tools (for
|
||||
example, assembly source produced by the compiler can be transformed into
|
||||
executable code by an assembler). The compilation graph is basically a list of
|
||||
edges; a special node named ``root`` is used to mark graph entry points.
|
||||
|
||||
Tool descriptions are represented as property lists: most properties
|
||||
in the example above should be self-explanatory; the ``sink`` property
|
||||
means that all options lacking an explicit description should be
|
||||
forwarded to this tool.
|
||||
Tool descriptions are represented as property lists: most properties in the
|
||||
example above should be self-explanatory; the ``sink`` property means that all
|
||||
options lacking an explicit description should be forwarded to this tool.
|
||||
|
||||
The ``LanguageMap`` associates a language name with a list of suffixes
|
||||
and is used for deciding which toolchain corresponds to a given input
|
||||
file.
|
||||
The ``LanguageMap`` associates a language name with a list of suffixes and is
|
||||
used for deciding which toolchain corresponds to a given input file.
|
||||
|
||||
To learn more about LLVMC customization, refer to the reference
|
||||
manual and plugin source code in the ``plugins`` directory.
|
||||
To learn more about writing your own drivers with LLVMC, refer to the reference
|
||||
manual and examples in the ``examples`` directory. Of a particular interest is
|
||||
the ``Skeleton`` example, which can serve as a template for your LLVMC-based
|
||||
drivers.
|
||||
|
||||
.. raw:: html
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user