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Document the plugin priority feature. 

llvm-svn: 60044
This commit is contained in:
Mikhail Glushenkov 2008-11-25 21:34:01 +00:00
parent b4ff5322c1
commit cb0ffa0182
1 changed files with 26 additions and 12 deletions
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38
llvm/tools/llvmc2/doc/LLVMC-Reference.rst
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@ -121,7 +121,7 @@ generic::
$ mv Simple.td MyPlugin.td
Note that the plugin source directory should be placed under
Note that the plugin source directory must be placed under
``$LLVMC_DIR/plugins`` to make use of the existing build
infrastructure. To build a version of the LLVMC executable called
``mydriver`` with your plugin compiled in, use the following command::
@ -129,13 +129,6 @@ infrastructure. To build a version of the LLVMC executable called
$ cd $LLVMC_DIR
$ make BUILTIN_PLUGINS=MyPlugin DRIVER_NAME=mydriver
When linking plugins dynamically, you'll usually want a 'bare-bones'
version of LLVMC that has no built-in plugins. It can be compiled with
the following command::
$ cd $LLVMC_DIR
$ make BUILTIN_PLUGINS=""
To build your plugin as a dynamic library, just ``cd`` to its source
directory and run ``make``. The resulting file will be called
``LLVMC$(LLVMC_PLUGIN).$(DLL_EXTENSION)`` (in our case,
@ -146,7 +139,28 @@ directory and run ``make``. The resulting file will be called
$ make
$ llvmc2 -load $LLVM_DIR/Release/lib/LLVMCSimple.so
In the future LLVMC will be able to load TableGen files directly.
Sometimes, you will want a 'bare-bones' version of LLVMC that has no
built-in plugins. It can be compiled with the following command::
$ cd $LLVMC_DIR
$ make BUILTIN_PLUGINS=""
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 ``.td`` 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.
Customizing LLVMC: the compilation graph
@ -194,9 +208,9 @@ The definition of the compilation graph (see file
As you can see, the edges can be either default or optional, where
optional edges are differentiated by an additional ``case`` expression
used to calculate the weight of this edge. Notice also that we refer
to tools via their names (as strings). This allows us to add edges to
an existing compilation graph without having to include all tool
definitions that it uses.
to tools via their names (as strings). This makes it possible to add
edges to an existing compilation graph in plugins without having to
know about all tool definitions used in the graph.
The default edges are assigned a weight of 1, and optional edges get a
weight of 0 + 2*N where N is the number of tests that evaluated to