Since the old llvmc was removed, rename llvmc2 to llvmc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60048 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvmc/doc/LLVMC-Tutorial.rst

@@ -0,0 +1,100 @@
+======================
+Tutorial - Using LLVMC
+======================
+:Author: Mikhail Glushenkov <foldr@codedegers.com>
+
+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.
+
+
+.. contents::
+
+
+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 -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.
+
+
+Using LLVMC to generate toolchain drivers
+=========================================
+
+LLVMC plugins are written mostly using TableGen [1]_, so you need to
+be familiar with it to get anything done.
+
+Start by compiling ``plugins/Simple/Simple.td``, which is a primitive
+wrapper for ``gcc``::
+
+    $ cd $LLVM_DIR/tools/llvmc
+    $ make DRIVER_NAME=mygcc BUILTIN_PLUGINS=Simple
+    $ cat > hello.c
+    [...]
+    $ mygcc hello.c
+    $ ./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 standalone dynamic library; this is described in the
+reference manual.
+
+Contents of the file ``Simple.td`` look like this::
+
+    // Include common definitions
+    include "llvm/CompilerDriver/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 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.
+
+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.
+
+References
+==========
+
+.. [1] TableGen Fundamentals
+       http://llvm.cs.uiuc.edu/docs/TableGenFundamentals.html