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+.. _getting_started:
+
+====================================
+Getting Started with the LLVM System  
+====================================
+
+Overview
+========
+
+Welcome to LLVM! In order to get started, you first need to know some basic
+information.
+
+First, LLVM comes in three pieces. The first piece is the LLVM suite. This
+contains all of the tools, libraries, and header files needed to use LLVM.  It
+contains an assembler, disassembler, bitcode analyzer and bitcode optimizer.  It
+also contains basic regression tests that can be used to test the LLVM tools and
+the Clang front end.
+
+The second piece is the `Clang <http://clang.llvm.org/>`_ front end.  This
+component compiles C, C++, Objective C, and Objective C++ code into LLVM
+bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
+LLVM tools from the LLVM suite.
+
+There is a third, optional piece called Test Suite.  It is a suite of programs
+with a testing harness that can be used to further test LLVM's functionality
+and performance.
+
+Getting Started Quickly (A Summary)
+===================================
+
+The LLVM Getting Started documentation may be out of date.  So, the `Clang
+Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a
+good place to start.
+
+Here's the short story for getting up and running quickly with LLVM:
+
+#. Read the documentation.
+#. Read the documentation.
+#. Remember that you were warned twice about reading the documentation.
+#. Checkout LLVM:
+
+   * ``cd where-you-want-llvm-to-live``
+   * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
+
+#. Checkout Clang:
+
+   * ``cd where-you-want-llvm-to-live``
+   * ``cd llvm/tools``
+   * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang``
+
+#. Checkout Compiler-RT:
+
+   * ``cd where-you-want-llvm-to-live``
+   * ``cd llvm/projects``
+   * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt``
+
+#. Get the Test Suite Source Code **[Optional]**
+
+   * ``cd where-you-want-llvm-to-live``
+   * ``cd llvm/projects``
+   * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite``
+
+#. Configure and build LLVM and Clang:
+
+   * ``cd where-you-want-to-build-llvm``
+   * ``mkdir build`` (for building without polluting the source dir)
+   * ``cd build``
+   * ``../llvm/configure [options]``
+     Some common options:
+
+     * ``--prefix=directory`` ---
+
+       Specify for *directory* the full pathname of where you want the LLVM
+       tools and libraries to be installed (default ``/usr/local``).
+
+     * ``--enable-optimized`` ---
+
+       Compile with optimizations enabled (default is NO).
+
+     * ``--enable-assertions`` ---
+
+       Compile with assertion checks enabled (default is YES).
+
+   * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
+     simultaneously.  This builds both LLVM and Clang for Debug+Asserts mode.
+     The --enabled-optimized configure option is used to specify a Release
+     build.
+
+   * ``make check-all`` --- This run the regression tests to ensure everything
+     is in working order.
+  
+   * ``make update`` --- This command is used to update all the svn repositories
+     at once, rather then having to ``cd`` into the individual repositories and
+     running ``svn update``.
+
+   * It is also possible to use CMake instead of the makefiles. With CMake it is
+     also possible to generate project files for several IDEs: Eclipse CDT4,
+     CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.
+
+   * If you get an "internal compiler error (ICE)" or test failures, see
+     `below`.
+
+Consult the `Getting Started with LLVM`_ section for detailed information on
+configuring and compiling LLVM.  See `Setting Up Your Environment`_ for tips
+that simplify working with the Clang front end and LLVM tools.  Go to `Program
+Layout`_ to learn about the layout of the source code tree.
+
+Requirements
+============
+
+Before you begin to use the LLVM system, review the requirements given below.
+This may save you some trouble by knowing ahead of time what hardware and
+software you will need.
+
+Hardware
+--------
+
+LLVM is known to work on the following platforms:
+
++-----------------+----------------------+-------------------------+
+|OS               |  Arch                | Compilers               |
++=================+======================+=========================+
+|AuroraUX         | x86\ :sup:`1`        | GCC                     |
++-----------------+----------------------+-------------------------+
+|Linux            | x86\ :sup:`1`        | GCC                     |
++-----------------+----------------------+-------------------------+
+|Linux            | amd64                | GCC                     |
++-----------------+----------------------+-------------------------+
+|Solaris          | V9 (Ultrasparc)      | GCC                     |
++-----------------+----------------------+-------------------------+
+|FreeBSD          | x86\ :sup:`1`        | GCC                     |
++-----------------+----------------------+-------------------------+
+|FreeBSD          | amd64                | GCC                     |
++-----------------+----------------------+-------------------------+
+|MacOS X\ :sup:`2`| PowerPC              | GCC                     |
++-----------------+----------------------+-------------------------+
+|MacOS X\ :sup:`9`| x86                  | GCC                     |
++-----------------+----------------------+-------------------------+
+|Cygwin/Win32     | x86\ :sup:`1, 8, 11` | GCC 3.4.X, binutils 2.20|
++-----------------+----------------------+-------------------------+
+
+LLVM has partial support for the following platforms:
+
++-------------------+----------------------+-------------------------------------------+
+|OS                 |  Arch                | Compilers                                 |
++===================+======================+===========================================+
+| Windows           | x86\ :sup:`1`        | Visual Studio 2000 or higher\ :sup:`4,5`  |
++-------------------+----------------------+-------------------------------------------+
+| AIX\ :sup:`3,4`   | PowerPC              | GCC                                       |
++-------------------+----------------------+-------------------------------------------+
+| Linux\ :sup:`3,5` | PowerPC              | GCC                                       |
++-------------------+----------------------+-------------------------------------------+
+| Linux\ :sup:`7`   | Alpha                | GCC                                       |
++-------------------+----------------------+-------------------------------------------+
+| Linux\ :sup:`7`   | Itanium (IA-64)      | GCC                                       |
++-------------------+----------------------+-------------------------------------------+
+| HP-UX\ :sup:`7`   | Itanium (IA-64)      | HP aCC                                    |
++-------------------+----------------------+-------------------------------------------+
+| Windows x64       | x86-64               | mingw-w64's GCC-4.5.x\ :sup:`12`          |
++-------------------+----------------------+-------------------------------------------+
+
+.. note::
+
+  Code generation supported for Pentium processors and up
+
+  #. Code generation supported for Pentium processors and up
+  #. Code generation supported for 32-bit ABI only
+  #. No native code generation
+  #. Build is not complete: one or more tools do not link or function
+  #. The GCC-based C/C++ frontend does not build
+  #. The port is done using the MSYS shell.
+  #. Native code generation exists but is not complete.
+  #. Binutils 2.20 or later is required to build the assembler generated by LLVM properly.
+  #. Xcode 2.5 and gcc 4.0.1 (Apple Build 5370) will trip internal LLVM assert
+     messages when compiled for Release at optimization levels greater than 0
+     (i.e., ``-O1`` and higher).  Add ``OPTIMIZE_OPTION="-O0"`` to the build
+     command line if compiling for LLVM Release or bootstrapping the LLVM
+     toolchain.
+  #. For MSYS/MinGW on Windows, be sure to install the MSYS version of the perl
+     package, and be sure it appears in your path before any Windows-based
+     versions such as Strawberry Perl and ActivePerl, as these have
+     Windows-specifics that will cause the build to fail.
+  #. To use LLVM modules on Win32-based system, you may configure LLVM
+     with ``--enable-shared``.
+
+  #. To compile SPU backend, you need to add ``LDFLAGS=-Wl,--stack,16777216`` to
+     configure.
+
+Note that you will need about 1-3 GB of space for a full LLVM build in Debug
+mode, depending on the system (it is so large because of all the debugging
+information and the fact that the libraries are statically linked into multiple
+tools).  If you do not need many of the tools and you are space-conscious, you
+can pass ``ONLY_TOOLS="tools you need"`` to make.  The Release build requires
+considerably less space.
+
+The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
+so.  If compilation is successful, the LLVM utilities should be able to
+assemble, disassemble, analyze, and optimize LLVM bitcode.  Code generation
+should work as well, although the generated native code may not work on your
+platform.
+
+Software
+--------
+
+Compiling LLVM requires that you have several software packages installed. The
+table below lists those required packages. The Package column is the usual name
+for the software package that LLVM depends on. The Version column provides
+"known to work" versions of the package. The Notes column describes how LLVM
+uses the package and provides other details.
+
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| Package                                                      | Version         | Notes                                       |
++==============================================================+=================+=============================================+
+| `GNU Make <http://savannah.gnu.org/projects/make>`_          | 3.79, 3.79.1    | Makefile/build processor                    |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `GCC <http://gcc.gnu.org/>`_                                 | 3.4.2           | C/C++ compiler\ :sup:`1`                    |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `TeXinfo <http://www.gnu.org/software/texinfo/>`_            | 4.5             | For building the CFE                        |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `SVN <http://subversion.tigris.org/project_packages.html>`_  | >=1.3           | Subversion access to LLVM\ :sup:`2`         |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `DejaGnu <http://savannah.gnu.org/projects/dejagnu>`_        | 1.4.2           | Automated test suite\ :sup:`3`              |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `tcl <http://www.tcl.tk/software/tcltk/>`_                   | 8.3, 8.4        | Automated test suite\ :sup:`3`              |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `expect <http://expect.nist.gov/>`_                          | 5.38.0          | Automated test suite\ :sup:`3`              |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `perl <http://www.perl.com/download.csp>`_                   | >=5.6.0         | Utilities                                   |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `GNU M4 <http://savannah.gnu.org/projects/m4>`_              | 1.4             | Macro processor for configuration\ :sup:`4` |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_      | 2.60            | Configuration script builder\ :sup:`4`      |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `GNU Automake <http://www.gnu.org/software/automake/>`_      | 1.9.6           | aclocal macro generator\ :sup:`4`           |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+| `libtool <http://savannah.gnu.org/projects/libtool>`_        | 1.5.22          | Shared library manager\ :sup:`4`            |
++--------------------------------------------------------------+-----------------+---------------------------------------------+
+
+.. note::
+
+   #. Only the C and C++ languages are needed so there's no need to build the
+      other languages for LLVM's purposes. See `below` for specific version
+      info.
+   #. You only need Subversion if you intend to build from the latest LLVM
+      sources. If you're working from a release distribution, you don't need
+      Subversion.
+   #. Only needed if you want to run the automated test suite in the
+      ``llvm/test`` directory.
+   #. If you want to make changes to the configure scripts, you will need GNU
+      autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
+      will also need automake (1.9.6). We only use aclocal from that package.
+
+Additionally, your compilation host is expected to have the usual plethora of
+Unix utilities. Specifically:
+
+* **ar** --- archive library builder
+* **bzip2** --- bzip2 command for distribution generation
+* **bunzip2** --- bunzip2 command for distribution checking
+* **chmod** --- change permissions on a file
+* **cat** --- output concatenation utility
+* **cp** --- copy files
+* **date** --- print the current date/time 
+* **echo** --- print to standard output
+* **egrep** --- extended regular expression search utility
+* **find** --- find files/dirs in a file system
+* **grep** --- regular expression search utility
+* **gzip** --- gzip command for distribution generation
+* **gunzip** --- gunzip command for distribution checking
+* **install** --- install directories/files 
+* **mkdir** --- create a directory
+* **mv** --- move (rename) files
+* **ranlib** --- symbol table builder for archive libraries
+* **rm** --- remove (delete) files and directories
+* **sed** --- stream editor for transforming output
+* **sh** --- Bourne shell for make build scripts
+* **tar** --- tape archive for distribution generation
+* **test** --- test things in file system
+* **unzip** --- unzip command for distribution checking
+* **zip** --- zip command for distribution generation
+
+.. _below:
+.. _check here:
+
+Broken versions of GCC and other tools
+--------------------------------------
+
+LLVM is very demanding of the host C++ compiler, and as such tends to expose
+bugs in the compiler.  In particular, several versions of GCC crash when trying
+to compile LLVM.  We routinely use GCC 4.2 (and higher) or Clang.  Other
+versions of GCC will probably work as well.  GCC versions listed here are known
+to not work.  If you are using one of these versions, please try to upgrade your
+GCC to something more recent.  If you run into a problem with a version of GCC
+not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_.  Please use
+the "``gcc -v``" command to find out which version of GCC you are using.
+
+**GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
+STL that effectively prevent it from compiling LLVM.
+
+**GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
+bogus template error.  This was fixed in later GCCs.
+
+**GCC 3.3.2**: This version of GCC suffered from a `serious bug
+<http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
+"``convert_from_eh_region_ranges_1``" GCC function.
+
+**Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
+not work.
+
+**SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
+others) does not compile LLVM correctly (it appears that exception handling is
+broken in some cases).  Please download the FSF 3.3.3 or upgrade to a newer
+version of GCC.
+
+**GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
+generator, causing an infinite loop in the llvm-gcc build when built with
+optimizations enabled (i.e. a release build).
+
+**GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
+generator at -O3, as with 3.4.0.  However gcc 3.4.2 (unlike 3.4.0) correctly
+compiles LLVM at -O2.  A work around is to build release LLVM builds with
+"``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
+
+**GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
+<http://llvm.org/PR1056>`_.
+
+**GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
+building with optimizations enabled.  It appears to work with "``make
+ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
+
+**IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
+
+**Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
+default with ENABLE_OPTIMIZED=1.  To work around this, build with
+"``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
+
+**GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
+compiling some files.  At the time of this writing, GCC mainline (4.2) did not
+share the problem.
+
+**GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
+<http://llvm.org/PR1063>`_ when compiling llvm itself into 64-bit code.  LLVM
+will appear to mostly work but will be buggy, e.g. failing portions of its
+testsuite.
+
+**GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
+platforms compiling md5.c gets a mangled constant.
+
+**GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
+miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
+symbols remaining in the table on destruction.
+
+**GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
+previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
+
+**Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
+<http://llvm.org/PR4145>`_ various problems related with link errors when using
+this GCC version.
+
+**Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
+
+**GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
+optimizations are turned on. The symptom is an infinite loop in
+``FoldingSetImpl::RemoveNode`` while running the code generator.
+
+**SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
+
+**GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
+``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
+the problem.
+
+**GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
+warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
+defined in a discarded section. You can safely ignore these messages as they are
+erroneous and the linkage is correct.  These messages disappear using ld 2.17.
+
+**GNU binutils 2.17**: Binutils 2.17 contains `a bug
+<http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`_ which causes huge link
+times (minutes instead of seconds) when building LLVM.  We recommend upgrading
+to a newer version (2.17.50.0.4 or later).
+
+**GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
+<http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`_ which causes
+intermittent failures when building LLVM with position independent code.  The
+symptom is an error about cyclic dependencies.  We recommend upgrading to a
+newer version of Gold.
+
+.. _Getting Started with LLVM:
+
+Getting Started with LLVM
+=========================
+
+The remainder of this guide is meant to get you up and running with LLVM and to
+give you some basic information about the LLVM environment.
+
+The later sections of this guide describe the `general layout`_ of the LLVM
+source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
+more information about LLVM or to get help via e-mail.
+
+Terminology and Notation
+------------------------
+
+Throughout this manual, the following names are used to denote paths specific to
+the local system and working environment.  *These are not environment variables
+you need to set but just strings used in the rest of this document below*.  In
+any of the examples below, simply replace each of these names with the
+appropriate pathname on your local system.  All these paths are absolute:
+
+``SRC_ROOT``
+
+  This is the top level directory of the LLVM source tree.
+
+``OBJ_ROOT``
+
+  This is the top level directory of the LLVM object tree (i.e. the tree where
+  object files and compiled programs will be placed.  It can be the same as
+  SRC_ROOT).
+
+.. _Setting Up Your Environment:
+
+Setting Up Your Environment
+---------------------------
+
+In order to compile and use LLVM, you may need to set some environment
+variables.
+
+``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
+
+  [Optional] This environment variable helps LLVM linking tools find the
+  locations of your bitcode libraries. It is provided only as a convenience
+  since you can specify the paths using the -L options of the tools and the
+  C/C++ front-end will automatically use the bitcode files installed in its
+  ``lib`` directory.
+
+Unpacking the LLVM Archives
+---------------------------
+
+If you have the LLVM distribution, you will need to unpack it before you can
+begin to compile it.  LLVM is distributed as a set of two files: the LLVM suite
+and the LLVM GCC front end compiled for your platform.  There is an additional
+test suite that is optional.  Each file is a TAR archive that is compressed with
+the gzip program.
+
+The files are as follows, with *x.y* marking the version number:
+
+``llvm-x.y.tar.gz``
+
+  Source release for the LLVM libraries and tools.
+
+``llvm-test-x.y.tar.gz``
+
+  Source release for the LLVM test-suite.
+
+``llvm-gcc-4.2-x.y.source.tar.gz``
+
+  Source release of the llvm-gcc-4.2 front end.  See README.LLVM in the root
+  directory for build instructions.
+
+``llvm-gcc-4.2-x.y-platform.tar.gz``
+
+  Binary release of the llvm-gcc-4.2 front end for a specific platform.
+
+Checkout LLVM from Subversion
+-----------------------------
+
+If you have access to our Subversion repository, you can get a fresh copy of the
+entire source code.  All you need to do is check it out from Subversion as
+follows:
+
+* ``cd where-you-want-llvm-to-live``
+* Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
+* Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
+
+This will create an '``llvm``' directory in the current directory and fully
+populate it with the LLVM source code, Makefiles, test directories, and local
+copies of documentation files.
+
+If you want to get a specific release (as opposed to the most recent revision),
+you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
+following releases are located in the following subdirectories of the '``tags``'
+directory:
+
+* Release 3.1: **RELEASE_31/final**
+* Release 3.0: **RELEASE_30/final**
+* Release 2.9: **RELEASE_29/final**
+* Release 2.8: **RELEASE_28**
+* Release 2.7: **RELEASE_27**
+* Release 2.6: **RELEASE_26**
+* Release 2.5: **RELEASE_25**
+* Release 2.4: **RELEASE_24**
+* Release 2.3: **RELEASE_23**
+* Release 2.2: **RELEASE_22**
+* Release 2.1: **RELEASE_21**
+* Release 2.0: **RELEASE_20**
+* Release 1.9: **RELEASE_19**
+* Release 1.8: **RELEASE_18**
+* Release 1.7: **RELEASE_17**
+* Release 1.6: **RELEASE_16**
+* Release 1.5: **RELEASE_15**
+* Release 1.4: **RELEASE_14**
+* Release 1.3: **RELEASE_13**
+* Release 1.2: **RELEASE_12**
+* Release 1.1: **RELEASE_11**
+* Release 1.0: **RELEASE_1**
+
+If you would like to get the LLVM test suite (a separate package as of 1.4), you
+get it from the Subversion repository:
+
+.. code:: bash
+
+  % cd llvm/projects
+  % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
+
+By placing it in the ``llvm/projects``, it will be automatically configured by
+the LLVM configure script as well as automatically updated when you run ``svn
+update``.
+
+GIT mirror
+----------
+
+GIT mirrors are available for a number of LLVM subprojects. These mirrors sync
+automatically with each Subversion commit and contain all necessary git-svn
+marks (so, you can recreate git-svn metadata locally). Note that right now
+mirrors reflect only ``trunk`` for each project. You can do the read-only GIT
+clone of LLVM via:
+
+.. code:: bash
+
+  % git clone http://llvm.org/git/llvm.git
+
+If you want to check out clang too, run:
+
+.. code:: bash
+
+  % git clone http://llvm.org/git/llvm.git
+  % cd llvm/tools
+  % git clone http://llvm.org/git/clang.git
+
+Since the upstream repository is in Subversion, you should use ``git
+pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
+in your clone.  To configure ``git pull`` to pass ``--rebase`` by default on the
+master branch, run the following command:
+
+.. code:: bash
+
+  % git config branch.master.rebase true
+
+Sending patches with Git
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Please read `Developer Policy <DeveloperPolicy.html#patches>`_, too.
+
+Assume ``master`` points the upstream and ``mybranch`` points your working
+branch, and ``mybranch`` is rebased onto ``master``.  At first you may check
+sanity of whitespaces:
+
+.. code:: bash
+
+  % git diff --check master..mybranch
+
+The easiest way to generate a patch is as below:
+
+.. code:: bash
+
+  % git diff master..mybranch > /path/to/mybranch.diff
+
+It is a little different from svn-generated diff. git-diff-generated diff has
+prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
+could be accepted with ``patch -p1 -N``.
+
+But you may generate patchset with git-format-patch. It generates by-each-commit
+patchset. To generate patch files to attach to your article:
+
+.. code:: bash
+
+  % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
+
+If you would like to send patches directly, you may use git-send-email or
+git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
+
+.. code:: bash
+
+  % git format-patch --attach master..mybranch --stdout | git imap-send
+
+Then, your .git/config should have [imap] sections.
+
+.. code:: bash
+
+  [imap]
+        host = imaps://imap.gmail.com
+        user = your.gmail.account@gmail.com
+        pass = himitsu!
+        port = 993
+        sslverify = false
+  ; in English
+        folder = "[Gmail]/Drafts"
+  ; example for Japanese, "Modified UTF-7" encoded.
+        folder = "[Gmail]/&amp;Tgtm+DBN-"
+  ; example for Traditional Chinese
+        folder = "[Gmail]/&amp;g0l6Pw-"
+
+For developers to work with git-svn
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To set up clone from which you can submit code using ``git-svn``, run:
+
+.. code:: bash
+
+  % git clone http://llvm.org/git/llvm.git
+  % cd llvm
+  % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
+  % git config svn-remote.svn.fetch :refs/remotes/origin/master
+  % git svn rebase -l  # -l avoids fetching ahead of the git mirror.
+
+  # If you have clang too:
+  % cd tools
+  % git clone http://llvm.org/git/clang.git
+  % cd clang
+  % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
+  % git config svn-remote.svn.fetch :refs/remotes/origin/master
+  % git svn rebase -l
+
+To update this clone without generating git-svn tags that conflict with the
+upstream git repo, run:
+
+.. code:: bash
+
+  % git fetch && (cd tools/clang && git fetch)  # Get matching revisions of both trees.
+  % git checkout master
+  % git svn rebase -l
+  % (cd tools/clang &&
+     git checkout master &&
+     git svn rebase -l)
+
+This leaves your working directories on their master branches, so you'll need to
+``checkout`` each working branch individually and ``rebase`` it on top of its
+parent branch.  (Note: This script is intended for relative newbies to git.  If
+you have more experience, you can likely improve on it.)
+
+The git-svn metadata can get out of sync after you mess around with branches and
+``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
+about files with uncommitted changes. The fix is to rebuild the metadata:
+
+.. code:: bash
+
+  % rm -rf .git/svn
+  % git svn rebase -l
+
+Local LLVM Configuration
+------------------------
+
+Once checked out from the Subversion repository, the LLVM suite source code must
+be configured via the ``configure`` script.  This script sets variables in the
+various ``*.in`` files, most notably ``llvm/Makefile.config`` and
+``llvm/include/Config/config.h``.  It also populates *OBJ_ROOT* with the
+Makefiles needed to begin building LLVM.
+
+The following environment variables are used by the ``configure`` script to
+configure the build system:
+
++------------+-----------------------------------------------------------+
+| Variable   | Purpose                                                   |
++============+===========================================================+
+| CC         | Tells ``configure`` which C compiler to use.  By default, |
+|            | ``configure`` will look for the first GCC C compiler in   |
+|            | ``PATH``.  Use this variable to override ``configure``\'s |
+|            | default behavior.                                         |
++------------+-----------------------------------------------------------+
+| CXX        | Tells ``configure`` which C++ compiler to use.  By        |
+|            | default, ``configure`` will look for the first GCC C++    |
+|            | compiler in ``PATH``.  Use this variable to override      |
+|            | ``configure``'s default behavior.                         |
++------------+-----------------------------------------------------------+
+
+The following options can be used to set or enable LLVM specific options:
+
+``--enable-optimized``
+
+  Enables optimized compilation (debugging symbols are removed and GCC
+  optimization flags are enabled). Note that this is the default setting if you
+  are using the LLVM distribution. The default behavior of an Subversion
+  checkout is to use an unoptimized build (also known as a debug build).
+
+``--enable-debug-runtime``
+
+  Enables debug symbols in the runtime libraries. The default is to strip debug
+  symbols from the runtime libraries.
+
+``--enable-jit``
+
+  Compile the Just In Time (JIT) compiler functionality.  This is not available
+  on all platforms.  The default is dependent on platform, so it is best to
+  explicitly enable it if you want it.
+
+``--enable-targets=target-option``
+
+  Controls which targets will be built and linked into llc. The default value
+  for ``target_options`` is "all" which builds and links all available targets.
+  The value "host-only" can be specified to build only a native compiler (no
+  cross-compiler targets available). The "native" target is selected as the
+  target of the build host. You can also specify a comma separated list of
+  target names that you want available in llc. The target names use all lower
+  case. The current set of targets is:
+
+    ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
+    x86, x86_64, xcore``.
+
+``--enable-doxygen``
+
+  Look for the doxygen program and enable construction of doxygen based
+  documentation from the source code. This is disabled by default because
+  generating the documentation can take a long time and producess 100s of
+  megabytes of output.
+
+``--with-udis86``
+
+  LLVM can use external disassembler library for various purposes (now it's used
+  only for examining code produced by JIT). This option will enable usage of
+  `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
+  disassembler library.
+
+To configure LLVM, follow these steps:
+
+#. Change directory into the object root directory:
+
+   .. code:: bash
+
+     % cd OBJ_ROOT
+
+#. Run the ``configure`` script located in the LLVM source tree:
+
+   .. code:: bash
+
+     % SRC_ROOT/configure --prefix=/install/path [other options]
+
+Compiling the LLVM Suite Source Code
+------------------------------------
+
+Once you have configured LLVM, you can build it.  There are three types of
+builds:
+
+Debug Builds
+
+  These builds are the default when one is using an Subversion checkout and
+  types ``gmake`` (unless the ``--enable-optimized`` option was used during
+  configuration).  The build system will compile the tools and libraries with
+  debugging information.  To get a Debug Build using the LLVM distribution the
+  ``--disable-optimized`` option must be passed to ``configure``.
+
+Release (Optimized) Builds
+
+  These builds are enabled with the ``--enable-optimized`` option to
+  ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
+  line.  For these builds, the build system will compile the tools and libraries
+  with GCC optimizations enabled and strip debugging information from the
+  libraries and executables it generates.  Note that Release Builds are default
+  when using an LLVM distribution.
+
+Profile Builds
+
+  These builds are for use with profiling.  They compile profiling information
+  into the code for use with programs like ``gprof``.  Profile builds must be
+  started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
+
+Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
+directory and issuing the following command:
+
+.. code:: bash
+
+  % gmake
+
+If the build fails, please `check here`_ to see if you are using a version of
+GCC that is known not to compile LLVM.
+
+If you have multiple processors in your machine, you may wish to use some of the
+parallel build options provided by GNU Make.  For example, you could use the
+command:
+
+.. code:: bash
+
+  % gmake -j2
+
+There are several special targets which are useful when working with the LLVM
+source code:
+
+``gmake clean``
+
+  Removes all files generated by the build.  This includes object files,
+  generated C/C++ files, libraries, and executables.
+
+``gmake dist-clean``
+
+  Removes everything that ``gmake clean`` does, but also removes files generated
+  by ``configure``.  It attempts to return the source tree to the original state
+  in which it was shipped.
+
+``gmake install``
+
+  Installs LLVM header files, libraries, tools, and documentation in a hierarchy
+  under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
+  defaults to ``/usr/local``.
+
+``gmake -C runtime install-bytecode``
+
+  Assuming you built LLVM into $OBJDIR, when this command is run, it will
+  install bitcode libraries into the GCC front end's bitcode library directory.
+  If you need to update your bitcode libraries, this is the target to use once
+  you've built them.
+
+Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
+these ``make`` targets and descriptions of other targets available.
+
+It is also possible to override default values from ``configure`` by declaring
+variables on the command line.  The following are some examples:
+
+``gmake ENABLE_OPTIMIZED=1``
+
+  Perform a Release (Optimized) build.
+
+``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
+
+  Perform a Release (Optimized) build without assertions enabled.
+ 
+``gmake ENABLE_OPTIMIZED=0``
+
+  Perform a Debug build.
+
+``gmake ENABLE_PROFILING=1``
+
+  Perform a Profiling build.
+
+``gmake VERBOSE=1``
+
+  Print what ``gmake`` is doing on standard output.
+
+``gmake TOOL_VERBOSE=1``
+
+  Ask each tool invoked by the makefiles to print out what it is doing on 
+  the standard output. This also implies ``VERBOSE=1``.
+
+Every directory in the LLVM object tree includes a ``Makefile`` to build it and
+any subdirectories that it contains.  Entering any directory inside the LLVM
+object tree and typing ``gmake`` should rebuild anything in or below that
+directory that is out of date.
+
+Cross-Compiling LLVM
+--------------------
+
+It is possible to cross-compile LLVM itself. That is, you can create LLVM
+executables and libraries to be hosted on a platform different from the platform
+where they are build (a Canadian Cross build). To configure a cross-compile,
+supply the configure script with ``--build`` and ``--host`` options that are
+different. The values of these options must be legal target triples that your
+GCC compiler supports.
+
+The result of such a build is executables that are not runnable on on the build
+host (--build option) but can be executed on the compile host (--host option).
+
+The Location of LLVM Object Files
+---------------------------------
+
+The LLVM build system is capable of sharing a single LLVM source tree among
+several LLVM builds.  Hence, it is possible to build LLVM for several different
+platforms or configurations using the same source tree.
+
+This is accomplished in the typical autoconf manner:
+
+* Change directory to where the LLVM object files should live:
+
+  .. code:: bash
+
+    % cd OBJ_ROOT
+
+* Run the ``configure`` script found in the LLVM source directory:
+
+  .. code:: bash
+
+    % SRC_ROOT/configure
+
+The LLVM build will place files underneath *OBJ_ROOT* in directories named after
+the build type:
+
+Debug Builds with assertions enabled (the default)
+
+  Tools
+
+    ``OBJ_ROOT/Debug+Asserts/bin``
+
+  Libraries
+
+    ``OBJ_ROOT/Debug+Asserts/lib``
+
+Release Builds
+
+  Tools
+
+    ``OBJ_ROOT/Release/bin``
+
+  Libraries
+
+    ``OBJ_ROOT/Release/lib``
+
+Profile Builds
+
+  Tools
+
+    ``OBJ_ROOT/Profile/bin``
+
+  Libraries
+
+    ``OBJ_ROOT/Profile/lib``
+
+Optional Configuration Items
+----------------------------
+
+If you're running on a Linux system that supports the `binfmt_misc
+<http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html>`_
+module, and you have root access on the system, you can set your system up to
+execute LLVM bitcode files directly. To do this, use commands like this (the
+first command may not be required if you are already using the module):
+
+.. code:: bash
+
+  % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
+  % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
+  % chmod u+x hello.bc   (if needed)
+  % ./hello.bc
+
+This allows you to execute LLVM bitcode files directly.  On Debian, you can also
+use this command instead of the 'echo' command above:
+
+.. code:: bash
+
+  % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
+
+.. _Program Layout:
+.. _general layout:
+
+Program Layout
+==============
+
+One useful source of information about the LLVM source base is the LLVM `doxygen
+<http://www.doxygen.org/>`_ documentation available at
+`<http://llvm.org/doxygen/>`_.  The following is a brief introduction to code
+layout:
+
+``llvm/examples``
+-----------------
+
+This directory contains some simple examples of how to use the LLVM IR and JIT.
+
+``llvm/include``
+----------------
+
+This directory contains public header files exported from the LLVM library. The
+three main subdirectories of this directory are:
+
+``llvm/include/llvm``
+
+  This directory contains all of the LLVM specific header files.  This directory
+  also has subdirectories for different portions of LLVM: ``Analysis``,
+  ``CodeGen``, ``Target``, ``Transforms``, etc...
+
+``llvm/include/llvm/Support``
+
+  This directory contains generic support libraries that are provided with LLVM
+  but not necessarily specific to LLVM. For example, some C++ STL utilities and
+  a Command Line option processing library store their header files here.
+
+``llvm/include/llvm/Config``
+
+  This directory contains header files configured by the ``configure`` script.
+  They wrap "standard" UNIX and C header files.  Source code can include these
+  header files which automatically take care of the conditional #includes that
+  the ``configure`` script generates.
+
+``llvm/lib``
+------------
+
+This directory contains most of the source files of the LLVM system. In LLVM,
+almost all code exists in libraries, making it very easy to share code among the
+different `tools`_.
+
+``llvm/lib/VMCore/``
+
+  This directory holds the core LLVM source files that implement core classes
+  like Instruction and BasicBlock.
+
+``llvm/lib/AsmParser/``
+
+  This directory holds the source code for the LLVM assembly language parser
+  library.
+
+``llvm/lib/BitCode/``
+
+  This directory holds code for reading and write LLVM bitcode.
+
+``llvm/lib/Analysis/``
+
+  This directory contains a variety of different program analyses, such as
+  Dominator Information, Call Graphs, Induction Variables, Interval
+  Identification, Natural Loop Identification, etc.
+
+``llvm/lib/Transforms/``
+
+  This directory contains the source code for the LLVM to LLVM program
+  transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
+  Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
+  Elimination, and many others.
+
+``llvm/lib/Target/``
+
+  This directory contains files that describe various target architectures for
+  code generation.  For example, the ``llvm/lib/Target/X86`` directory holds the
+  X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
+  backend.
+    
+``llvm/lib/CodeGen/``
+
+  This directory contains the major parts of the code generator: Instruction
+  Selector, Instruction Scheduling, and Register Allocation.
+
+``llvm/lib/MC/``
+
+  (FIXME: T.B.D.)
+
+``llvm/lib/Debugger/``
+
+  This directory contains the source level debugger library that makes it
+  possible to instrument LLVM programs so that a debugger could identify source
+  code locations at which the program is executing.
+
+``llvm/lib/ExecutionEngine/``
+
+  This directory contains libraries for executing LLVM bitcode directly at
+  runtime in both interpreted and JIT compiled fashions.
+
+``llvm/lib/Support/``
+
+  This directory contains the source code that corresponds to the header files
+  located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
+
+``llvm/projects``
+-----------------
+
+This directory contains projects that are not strictly part of LLVM but are
+shipped with LLVM. This is also the directory where you should create your own
+LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
+up your own project.
+
+``llvm/runtime``
+----------------
+
+This directory contains libraries which are compiled into LLVM bitcode and used
+when linking programs with the Clang front end.  Most of these libraries are
+skeleton versions of real libraries; for example, libc is a stripped down
+version of glibc.
+
+Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
+to compile.
+
+``llvm/test``
+-------------
+
+This directory contains feature and regression tests and other basic sanity
+checks on the LLVM infrastructure. These are intended to run quickly and cover a
+lot of territory without being exhaustive.
+
+``test-suite``
+--------------
+
+This is not a directory in the normal llvm module; it is a separate Subversion
+module that must be checked out (usually to ``projects/test-suite``).  This
+module contains a comprehensive correctness, performance, and benchmarking test
+suite for LLVM. It is a separate Subversion module because not every LLVM user
+is interested in downloading or building such a comprehensive test suite. For
+further details on this test suite, please see the `Testing
+Guide <TestingGuide.html>`_ document.
+
+.. _tools:
+
+``llvm/tools``
+--------------
+
+The **tools** directory contains the executables built out of the libraries
+above, which form the main part of the user interface.  You can always get help
+for a tool by typing ``tool_name -help``.  The following is a brief introduction
+to the most important tools.  More detailed information is in
+the `Command Guide <CommandGuide/index.html>`_.
+
+``bugpoint``
+
+  ``bugpoint`` is used to debug optimization passes or code generation backends
+  by narrowing down the given test case to the minimum number of passes and/or
+  instructions that still cause a problem, whether it is a crash or
+  miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
+  ``bugpoint``.
+
+``llvm-ar``
+
+  The archiver produces an archive containing the given LLVM bitcode files,
+  optionally with an index for faster lookup.
+  
+``llvm-as``
+
+  The assembler transforms the human readable LLVM assembly to LLVM bitcode.
+
+``llvm-dis``
+
+  The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
+
+``llvm-link``
+
+  ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
+  program.
+  
+``lli``
+
+  ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
+  (although very slowly...). For architectures that support it (currently x86,
+  Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
+  compiler (if the functionality was compiled in), and will execute the code
+  *much* faster than the interpreter.
+
+``llc``
+
+  ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
+  native code assembly file or to C code (with the ``-march=c`` option).
+
+``opt``
+
+  ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
+  (which are specified on the command line), and then outputs the resultant
+  bitcode.  The '``opt -help``' command is a good way to get a list of the
+  program transformations available in LLVM.
+
+  ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
+  file and print out the results.  It is primarily useful for debugging
+  analyses, or familiarizing yourself with what an analysis does.
+
+``llvm/utils``
+--------------
+
+This directory contains utilities for working with LLVM source code, and some of
+the utilities are actually required as part of the build process because they
+are code generators for parts of LLVM infrastructure.
+
+
+``codegen-diff``
+
+  ``codegen-diff`` is a script that finds differences between code that LLC
+  generates and code that LLI generates. This is a useful tool if you are
+  debugging one of them, assuming that the other generates correct output. For
+  the full user manual, run ```perldoc codegen-diff'``.
+
+``emacs/``
+
+  The ``emacs`` directory contains syntax-highlighting files which will work
+  with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
+  assembly files and TableGen description files. For information on how to use
+  the syntax files, consult the ``README`` file in that directory.
+
+``getsrcs.sh``
+
+  The ``getsrcs.sh`` script finds and outputs all non-generated source files,
+  which is useful if one wishes to do a lot of development across directories
+  and does not want to individually find each file. One way to use it is to run,
+  for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
+  tree.
+
+``llvmgrep``
+
+  This little tool performs an ``egrep -H -n`` on each source file in LLVM and
+  passes to it a regular expression provided on ``llvmgrep``'s command
+  line. This is a very efficient way of searching the source base for a
+  particular regular expression.
+
+``makellvm``
+
+  The ``makellvm`` script compiles all files in the current directory and then
+  compiles and links the tool that is the first argument. For example, assuming
+  you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
+  path, simply running ``makellvm llc`` will make a build of the current
+  directory, switch to directory ``llvm/tools/llc`` and build it, causing a
+  re-linking of LLC.
+
+``TableGen/``
+
+  The ``TableGen`` directory contains the tool used to generate register
+  descriptions, instruction set descriptions, and even assemblers from common
+  TableGen description files.
+
+``vim/``
+
+  The ``vim`` directory contains syntax-highlighting files which will work with
+  the VIM editor, providing syntax highlighting support for LLVM assembly files
+  and TableGen description files. For information on how to use the syntax
+  files, consult the ``README`` file in that directory.
+
+.. _simple example:
+
+An Example Using the LLVM Tool Chain
+====================================
+
+This section gives an example of using LLVM with the Clang front end.
+
+Example with clang
+------------------
+
+#. First, create a simple C file, name it 'hello.c':
+
+   .. code:: c
+
+     #include <stdio.h>
+
+     int main() {
+       printf("hello world\n");
+       return 0;
+     }
+
+#. Next, compile the C file into a native executable:
+
+   .. code:: bash
+
+     % clang hello.c -o hello
+
+   .. note::
+
+     Clang works just like GCC by default.  The standard -S and -c arguments
+     work as usual (producing a native .s or .o file, respectively).
+
+#. Next, compile the C file into a LLVM bitcode file:
+
+   .. code:: bash
+
+     % clang -O3 -emit-llvm hello.c -c -o hello.bc
+
+   The -emit-llvm option can be used with the -S or -c options to emit an LLVM
+   ``.ll`` or ``.bc`` file (respectively) for the code.  This allows you to use
+   the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
+
+#. Run the program in both forms. To run the program, use:
+
+   .. code:: bash
+
+      % ./hello
+ 
+   and
+
+   .. code:: bash
+
+     % lli hello.bc
+
+   The second examples shows how to invoke the LLVM JIT, `lli
+   <CommandGuide/html/lli.html>`_.
+
+#. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
+
+   .. code:: bash
+
+     % llvm-dis < hello.bc | less
+
+#. Compile the program to native assembly using the LLC code generator:
+
+   .. code:: bash
+
+     % llc hello.bc -o hello.s
+
+#. Assemble the native assembly language file into a program:
+
+   .. code:: bash
+
+     **Solaris:** % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
+
+     **Others:**  % gcc hello.s -o hello.native
+
+#. Execute the native code program:
+
+   .. code:: bash
+
+     % ./hello.native
+
+   Note that using clang to compile directly to native code (i.e. when the
+   ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
+
+Common Problems
+===============
+
+If you are having problems building or using LLVM, or if you have any other
+general questions about LLVM, please consult the `Frequently Asked
+Questions <FAQ.html>`_ page.
+
+.. _links:
+
+Links
+=====
+
+This document is just an **introduction** on how to use LLVM to do some simple
+things... there are many more interesting and complicated things that you can do
+that aren't documented here (but we'll gladly accept a patch if you want to
+write something up!).  For more information about LLVM, check out:
+
+* `LLVM Homepage <http://llvm.org/>`_
+* `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
+* `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_