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Update documentation, add examples.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51736 91177308-0d34-0410-b5e6-96231b3b80d8
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Mikhail Glushenkov 2008-05-30 06:14:42 +00:00
parent 1e4bab2c02
commit cd0858e170
5 changed files with 238 additions and 74 deletions
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5
tools/llvmc2/Makefile
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@ -15,8 +15,9 @@ REQUIRES_EH := 1
include $(LEVEL)/Makefile.common
GRAPH=Graph.td
TOOLS=Tools.td
TOOLS_SOURCE=$(GRAPH) $(TOOLS) Common.td
$(GRAPH) : Common.td
Graph.td : Tools.td
TOOLS_SOURCE=$(GRAPH)
# TOFIX: integrate this part into Makefile.rules?
# The degree of horrorshowness in that file is too much for me atm.

205
tools/llvmc2/doc/LLVMC-Reference.rst
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@ -1,5 +1,5 @@
Tutorial - Writing LLVMC Configuration files
=============================================
Customizing LLVMC: Reference Manual
===================================
LLVMC is a generic compiler driver, designed to be customizable and
extensible. It plays the same role for LLVM as the ``gcc`` program
@ -10,8 +10,7 @@ are completely customizable - in fact, LLVMC knows nothing about the
specifics of transformation (even the command-line options are mostly
not hard-coded) and regards the transformation structure as an
abstract graph. This makes it possible to adapt LLVMC for other
purposes - for example, as a build tool for game resources. This
tutorial describes the basic usage and configuration of LLVMC.
purposes - for example, as a build tool for game resources.
Because LLVMC employs TableGen [1]_ as its configuration language, you
need to be familiar with it to customize LLVMC.
@ -19,19 +18,21 @@ need to be familiar with it to customize LLVMC.
Compiling with LLVMC
--------------------
In general, LLVMC tries to be command-line compatible with ``gcc`` as
much as possible, so most of the familiar options work::
LLVMC tries hard to be as compatible with ``gcc`` as possible,
although there are some small differences. Most of the time, however,
you shouldn't be able to notice them::
$ # This works as expected:
$ llvmc2 -O3 -Wall hello.cpp
$ ./a.out
hello
One nice feature of LLVMC is that you don't have to distinguish
One nice feature of LLVMC is that one doesn't have to distinguish
between different compilers for different languages (think ``g++`` and
``gcc``) - the right toolchain is chosen automatically based on input
language names (which are, in turn, determined from file extension). If
you want to force files ending with ".c" compile as C++, use the
``-x`` option, just like you would do it with ``gcc``::
language names (which are, in turn, determined from file
extensions). If you want to force files ending with ".c" to compile as
C++, use the ``-x`` option, just like you would do it with ``gcc``::
$ llvmc2 -x c hello.cpp
$ # hello.cpp is really a C file
@ -49,25 +50,36 @@ impossible for LLVMC to choose the right linker in that case::
$ ./a.out
hello
For further help on command-line LLVMC usage, refer to the ``llvmc
--help`` output.
Customizing LLVMC: the compilation graph
----------------------------------------
At the time of writing LLVMC does not support on-the-fly reloading of
configuration, so to customize LLVMC you'll have to edit and recompile
the source code (which lives under ``$LLVM_DIR/tools/llvmc2``). The
relevant files are ``Common.td``, ``Tools.td`` and ``Example.td``.
configuration, so to customize LLVMC you'll have to recompile the
source code (which lives under ``$LLVM_DIR/tools/llvmc2``). The
default configuration files are ``Common.td`` (contains common
definitions, don't forget to ``include`` it in your configuration
files), ``Tools.td`` (tool descriptions) and ``Graph.td`` (compilation
graph definition).
Internally, LLVMC stores information about possible transformations in
form of a graph. Nodes in this graph represent tools, and edges
between two nodes represent a transformation path. A special "root"
node represents entry points for the transformations. LLVMC also
assigns a weight to each edge (more on that below) to choose between
several alternative edges.
To compile LLVMC with your own configuration file (say,``MyGraph.td``),
run ``make`` like this::
The definition of the compilation graph (see file ``Example.td``) is
$ cd $LLVM_DIR/tools/llvmc2
$ make GRAPH=MyGraph.td TOOLNAME=my_llvmc
This will build an executable named ``my_llvmc``. There are also
several sample configuration files in the ``llvmc2/examples``
subdirectory that should help to get you started.
Internally, LLVMC stores information about possible source
transformations in form of a graph. Nodes in this graph represent
tools, and edges between two nodes represent a transformation path. A
special "root" node is used to mark entry points for the
transformations. LLVMC also assigns a weight to each edge (more on
this later) to choose between several alternative edges.
The definition of the compilation graph (see file ``Graph.td``) is
just a list of edges::
def CompilationGraph : CompilationGraph<[
@ -84,25 +96,46 @@ just a list of edges::
...
OptionalEdge<llvm_gcc_assembler, llvm_gcc_cpp_linker,
[(if_input_languages_contain "c++"),
(or (parameter_equals "linker", "g++"),
(parameter_equals "linker", "c++"))]>,
(case (input_languages_contain "c++"), (inc_weight),
(or (parameter_equals "linker", "g++"),
(parameter_equals "linker", "c++")), (inc_weight))>,
...
]>;
As you can see, the edges can be either default or optional, where
optional edges are differentiated by sporting a list of patterns (or
edge properties) which are used to calculate the edge's weight. 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 succesful edge property
matches. When passing an input file through the graph, LLVMC picks the
edge with the maximum weight. To avoid ambiguity, there should be only
one default edge between two nodes (with the exception of the root
node, which gets a special treatment - there you are allowed to
specify one default edge *per language*).
optional edges are differentiated by sporting a ``case`` expression
used to calculate the edge's weight.
* Possible edge properties are:
The default edges are assigned a weight of 1, and optional edges get a
weight of 0 + 2*N where N is the number of tests that evaluated to
true in the ``case`` expression. It is also possible to provide an
integer parameter to ``inc_weight`` and ``dec_weight`` - in this case,
the weight is increased (or decreased) by the provided value instead
of the default 2.
When passing an input file through the graph, LLVMC picks the edge
with the maximum weight. To avoid ambiguity, there should be only one
default edge between two nodes (with the exception of the root node,
which gets a special treatment - there you are allowed to specify one
default edge *per language*).
To get a visual representation of the compilation graph (useful for
debugging), run ``llvmc2 --view-graph``. You will need ``dot`` and
``gsview`` installed for this to work properly.
The 'case' construct
--------------------
The 'case' construct can be used to calculate weights for optional
edges and to choose between several alternative command line strings
in the ``cmd_line`` tool property. It is designed after the
similarly-named construct in functional languages and takes the
form ``(case (test_1), statement_1, (test_2), statement_2,
... (test_N), statement_N)``.
* Possible tests are:
- ``switch_on`` - Returns true if a given command-line option is
provided by the user. Example: ``(switch_on "opt")``. Note that
@ -116,35 +149,28 @@ specify one default edge *per language*).
- ``element_in_list`` - Returns true if a command-line parameter list
includes a given value. Example: ``(parameter_in_list "l", "pthread")``.
- ``if_input_languages_contain`` - Returns true if a given input
language belongs to the current input language set.
- ``input_languages_contain`` - Returns true if a given language
belongs to the current input language set. Example:
```(input_languages_contain "c++")``.
- ``and`` - Edge property combinator. Returns true if all of its
arguments return true. Used like this: ``(and (prop1), (prop2),
... (propN))``. Nesting is allowed, but not encouraged.
- ``default`` - Always evaluates to true. Should be used
- ``or`` - Edge property combinator that returns true if any one of its
arguments returns true. Example: ``(or (prop1), (prop2), ... (propN))``.
- ``and`` - A standard logical combinator that returns true iff all
of its arguments return true. Used like this: ``(and (test1),
(test2), ... (testN))``. Nesting of ``and`` and ``or`` is allowed,
but not encouraged.
- ``weight`` - Makes it possible to explicitly specify the quantity
added to the edge weight if this edge property matches. Used like
this: ``(weight N, (prop))``. The inner property can include
``and`` and ``or`` combinators. When N is equal to 2, equivalent
to ``(prop)``.
Example: ``(weight 8, (and (switch_on "a"), (switch_on "b")))``.
To get a visual representation of the compilation graph (useful for
debugging), run ``llvmc2 --view-graph``. You will need ``dot`` and
``gsview`` installed for this to work properly.
- ``or`` - Another logical combinator that returns true only if any
one of its arguments returns true. Example: ``(or (test1),
(test2), ... (testN))``.
Writing a tool description
--------------------------
As was said earlier, nodes in the compilation graph represent tools. A
tool definition looks like this (taken from the ``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 ``Tools.td`` file)::
def llvm_gcc_cpp : Tool<[
(in_language "c++"),
@ -156,9 +182,9 @@ tool definition looks like this (taken from the ``Tools.td`` file)::
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-evident. The ``sink`` property
means that this tool should be passed all command-line options that
aren't handled by the other tools.
properties; most of them should be self-explanatory. The ``sink``
property means that this tool should be passed all command-line
options that lack explicit descriptions.
The complete list of the currently implemented tool properties follows:
@ -170,9 +196,10 @@ The complete list of the currently implemented tool properties follows:
- ``output_suffix`` - output file suffix.
- ``cmd_line`` - the actual command used to run the tool. You can use
``$INFILE`` and ``$OUTFILE`` variables, as well as output
redirection with ``>``.
- ``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 (more on this below).
- ``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.
@ -188,14 +215,16 @@ The next tool definition is slightly more complex::
(output_suffix "out"),
(cmd_line "llvm-gcc $INFILE -o $OUTFILE"),
(join),
(prefix_list_option "L", (forward), (help "add a directory to link path")),
(prefix_list_option "l", (forward), (help "search a library when linking")),
(prefix_list_option "Wl", (unpack_values), (help "pass options to linker"))
(prefix_list_option "L", (forward),
(help "add a directory to link path")),
(prefix_list_option "l", (forward),
(help "search a library when linking")),
(prefix_list_option "Wl", (unpack_values),
(help "pass options to linker"))
]>;
This tool has a "join" property, which means that it behaves like a
linker (because of that this tool should be the last in the
toolchain). This tool also defines several command-line options: ``-l``,
linker. This tool also defines several command-line options: ``-l``,
``-L`` and ``-Wl`` which have their usual meaning. An option has two
attributes: a name and a (possibly empty) list of properties. All
currently implemented option types and properties are described below:
@ -223,6 +252,9 @@ currently implemented option types and properties are described below:
- ``forward`` - forward this option unchanged.
- ``output_suffix`` - modify the output suffix of this
tool. Example : ``(switch "E", (output_suffix "i")``.
- ``stop_compilation`` - stop compilation after this phase.
- ``unpack_values`` - used for for splitting and forwarding
@ -230,19 +262,48 @@ currently implemented option types and properties are described below:
converted to ``-foo=bar -baz`` and appended to the tool invocation
command.
- ``help`` - help string associated with this option.
- ``help`` - help string associated with this option. Used for
``--help`` output.
- ``required`` - this option is obligatory.
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 names
in the configuration file. This can be achieved via the mechanism of
hooks - to compile LLVMC with your hooks, just drop a .cpp file into
``tools/llvmc2`` directory. Hooks should live in the ``hooks``
namespace and have the signature ``std::string hooks::MyHookName
(void)``. They can be used from the ``cmd_line`` tool property::
(cmd_line "$CALL(MyHook)/path/to/file -o $CALL(AnotherHook)")
It is also possible to use environment variables in the same manner::
(cmd_line "$ENV(VAR1)/path/to/file -o $ENV(VAR2)")
To change the command line string based on user-provided options use
the ``case`` expression (which we have already seen before)::
(cmd_line
(case
(switch_on "E"),
"llvm-g++ -E -x c $INFILE -o $OUTFILE",
(default),
"llvm-g++ -c -x c $INFILE -o $OUTFILE -emit-llvm"))
Language map
------------
One last thing that you need to modify when adding support for a new
language to LLVMC is the language map, which defines mappings from
One last thing that you will need to modify when adding support for a
new language to LLVMC is the language map, which defines mappings from
file extensions to language names. It is used to choose the proper
toolchain based on the input. Language map definition is located in
the file ``Tools.td`` and looks like this::
toolchain(s) for a given input file set. Language map definition is
located in the file ``Tools.td`` and looks like this::
def LanguageMap : LanguageMap<
[LangToSuffixes<"c++", ["cc", "cp", "cxx", "cpp", "CPP", "c++", "C"]>,

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tools/llvmc2/doc/LLVMC-Tutorial.rst Normal file
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@ -0,0 +1,87 @@
Tutorial - Using 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. This
tutorial describes the basic usage and configuration of LLVMC.
Compiling with LLVMC
--------------------
In general, LLVMC tries to be command-line compatible with ``gcc`` as
much as possible, so most of the familiar options work::
$ llvmc2 -O3 -Wall hello.cpp
$ ./a.out
hello
For further help on command-line LLVMC usage, refer to the ``llvmc
--help`` output.
Using LLVMC to generate toolchain drivers
-----------------------------------------
At the time of writing LLVMC does not support on-the-fly reloading of
configuration, so it will be necessary to recompile its source
code. LLVMC uses TableGen [1]_ as its configuration language, so
you'll need to familiar with it.
Start by compiling ``examples/Simple.td``, which is a simple wrapper
for ``gcc``::
$ cd $LLVM_DIR/tools/llvmc2
$ make TOOLNAME=mygcc GRAPH=examples/Simple.td
$ edit hello.c
$ mygcc hello.c
$ ./hello.out
Hello
Contents of the file ``Simple.td`` look like this::
// Include common definitions
include "Common.td"
// Tool descriptions
def gcc : Tool<
[(in_language "c"),
(out_language "executable"),
(output_suffix "out"),
(cmd_line "gcc $INFILE -o $OUTFILE"),
(sink)
]>;
// Language map
def LanguageMap : LanguageMap<[LangToSuffixes<"c", ["c"]>]>;
// Compilation graph
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.
At the heart of LLVMC is the idea of a transformation graph: vertices
in this graph are tools, and edges signify that there is a
transformation path between two tools (for example, assembly source
produced by the compiler can be transformed into executable code by an
assembler). A special node named ``root`` is used to mark graph entry
points.
Tool descriptions are basically lists of properties: 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.
``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 sample configuration files in the ``examples`` directory.
References
==========
.. [1] TableGen Fundamentals
http://llvm.cs.uiuc.edu/docs/TableGenFundamentals.html

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@ -0,0 +1,15 @@
// A simple wrapper for gcc.
include "Common.td"
def gcc : Tool<
[(in_language "c"),
(out_language "executable"),
(output_suffix "out"),
(cmd_line "gcc $INFILE -o $OUTFILE"),
(sink)
]>;
def LanguageMap : LanguageMap<[LangToSuffixes<"c", ["c"]>]>;
def CompilationGraph : CompilationGraph<[Edge<root, gcc>]>;