1==================================================================
2Getting Started with the LLVM System using Microsoft Visual Studio
3==================================================================
4
5.. contents::
6   :local:
7
8
9Overview
10========
11Welcome to LLVM on Windows! This document only covers LLVM on Windows using
12Visual Studio, not mingw or cygwin. In order to get started, you first need to
13know some basic information.
14
15There are many different projects that compose LLVM. The first is the LLVM
16suite. This contains all of the tools, libraries, and header files needed to
17use LLVM. It contains an assembler, disassembler,
18bitcode analyzer and bitcode optimizer. It also contains a test suite that can
19be used to test the LLVM tools.
20
21Another useful project on Windows is `Clang <http://clang.llvm.org/>`_.
22Clang is a C family ([Objective]C/C++) compiler. Clang mostly works on
23Windows, but does not currently understand all of the Microsoft extensions
24to C and C++. Because of this, clang cannot parse the C++ standard library
25included with Visual Studio, nor parts of the Windows Platform SDK. However,
26most standard C programs do compile. Clang can be used to emit bitcode,
27directly emit object files or even linked executables using Visual Studio's
28``link.exe``.
29
30The large LLVM test suite cannot be run on the Visual Studio port at this
31time.
32
33Most of the tools build and work.  ``bugpoint`` does build, but does
34not work.
35
36Additional information about the LLVM directory structure and tool chain
37can be found on the main :doc:`GettingStarted` page.
38
39
40Requirements
41============
42Before you begin to use the LLVM system, review the requirements given
43below.  This may save you some trouble by knowing ahead of time what hardware
44and software you will need.
45
46Hardware
47--------
48Any system that can adequately run Visual Studio 2013 is fine. The LLVM
49source tree and object files, libraries and executables will consume
50approximately 3GB.
51
52Software
53--------
54You will need Visual Studio 2013 or higher.
55
56You will also need the `CMake <http://www.cmake.org/>`_ build system since it
57generates the project files you will use to build with.
58
59If you would like to run the LLVM tests you will need `Python
60<http://www.python.org/>`_. Version 2.7 and newer are known to work. You will
61need `GnuWin32 <http://gnuwin32.sourceforge.net/>`_ tools, too.
62
63Do not install the LLVM directory tree into a path containing spaces (e.g.
64``C:\Documents and Settings\...``) as the configure step will fail.
65
66
67Getting Started
68===============
69Here's the short story for getting up and running quickly with LLVM:
70
711. Read the documentation.
722. Seriously, read the documentation.
733. Remember that you were warned twice about reading the documentation.
744. Get the Source Code
75
76   * With the distributed files:
77
78      1. ``cd <where-you-want-llvm-to-live>``
79      2. ``gunzip --stdout llvm-VERSION.tar.gz | tar -xvf -``
80         (*or use WinZip*)
81      3. ``cd llvm``
82
83   * With anonymous Subversion access:
84
85      1. ``cd <where-you-want-llvm-to-live>``
86      2. ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
87      3. ``cd llvm``
88
895. Use `CMake <http://www.cmake.org/>`_ to generate up-to-date project files:
90
91   * Once CMake is installed then the simplest way is to just start the
92     CMake GUI, select the directory where you have LLVM extracted to, and
93     the default options should all be fine.  One option you may really
94     want to change, regardless of anything else, might be the
95     ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
96     once compiling is complete, although installation is not mandatory for
97     using LLVM.  Another important option is ``LLVM_TARGETS_TO_BUILD``,
98     which controls the LLVM target architectures that are included on the
99     build.
100   * See the :doc:`LLVM CMake guide <CMake>` for detailed information about
101     how to configure the LLVM build.
102   * CMake generates project files for all build types. To select a specific
103     build type, use the Configuration manager from the VS IDE or the
104     ``/property:Configuration`` command line option when using MSBuild.
105
1066. Start Visual Studio
107
108   * In the directory you created the project files will have an ``llvm.sln``
109     file, just double-click on that to open Visual Studio.
110
1117. Build the LLVM Suite:
112
113   * The projects may still be built individually, but to build them all do
114     not just select all of them in batch build (as some are meant as
115     configuration projects), but rather select and build just the
116     ``ALL_BUILD`` project to build everything, or the ``INSTALL`` project,
117     which first builds the ``ALL_BUILD`` project, then installs the LLVM
118     headers, libs, and other useful things to the directory set by the
119     ``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake.
120   * The Fibonacci project is a sample program that uses the JIT. Modify the
121     project's debugging properties to provide a numeric command line argument
122     or run it from the command line.  The program will print the
123     corresponding fibonacci value.
124
1258. Test LLVM in Visual Studio:
126
127   * If ``%PATH%`` does not contain GnuWin32, you may specify
128     ``LLVM_LIT_TOOLS_DIR`` on CMake for the path to GnuWin32.
129   * You can run LLVM tests by merely building the project "check". The test
130     results will be shown in the VS output window.
131
1329. Test LLVM on the command line:
133
134   * The LLVM tests can be run by changing directory to the llvm source
135     directory and running:
136
137     .. code-block:: bat
138
139        C:\..\llvm> python ..\build\bin\llvm-lit --param build_config=Win32 --param build_mode=Debug --param llvm_site_config=../build/test/lit.site.cfg test
140
141     This example assumes that Python is in your PATH variable, you
142     have built a Win32 Debug version of llvm with a standard out of
143     line build. You should not see any unexpected failures, but will
144     see many unsupported tests and expected failures.
145
146     A specific test or test directory can be run with:
147
148     .. code-block:: bat
149
150        C:\..\llvm> python ..\build\bin\llvm-lit --param build_config=Win32 --param build_mode=Debug --param llvm_site_config=../build/test/lit.site.cfg test/path/to/test
151
152
153An Example Using the LLVM Tool Chain
154====================================
155
1561. First, create a simple C file, name it '``hello.c``':
157
158   .. code-block:: c
159
160      #include <stdio.h>
161      int main() {
162        printf("hello world\n");
163        return 0;
164      }
165
1662. Next, compile the C file into an LLVM bitcode file:
167
168   .. code-block:: bat
169
170      C:\..> clang -c hello.c -emit-llvm -o hello.bc
171
172   This will create the result file ``hello.bc`` which is the LLVM bitcode
173   that corresponds the compiled program and the library facilities that
174   it required.  You can execute this file directly using ``lli`` tool,
175   compile it to native assembly with the ``llc``, optimize or analyze it
176   further with the ``opt`` tool, etc.
177
178   Alternatively you can directly output an executable with clang with:
179
180   .. code-block:: bat
181
182      C:\..> clang hello.c -o hello.exe
183
184   The ``-o hello.exe`` is required because clang currently outputs ``a.out``
185   when neither ``-o`` nor ``-c`` are given.
186
1873. Run the program using the just-in-time compiler:
188
189   .. code-block:: bat
190
191      C:\..> lli hello.bc
192
1934. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
194
195   .. code-block:: bat
196
197      C:\..> llvm-dis < hello.bc | more
198
1995. Compile the program to object code using the LLC code generator:
200
201   .. code-block:: bat
202
203      C:\..> llc -filetype=obj hello.bc
204
2056. Link to binary using Microsoft link:
206
207   .. code-block:: bat
208
209      C:\..> link hello.obj -defaultlib:libcmt
210
2117. Execute the native code program:
212
213   .. code-block:: bat
214
215      C:\..> hello.exe
216
217
218Common Problems
219===============
220If you are having problems building or using LLVM, or if you have any other
221general questions about LLVM, please consult the :doc:`Frequently Asked Questions
222<FAQ>` page.
223
224
225Links
226=====
227This document is just an **introduction** to how to use LLVM to do some simple
228things... there are many more interesting and complicated things that you can
229do that aren't documented here (but we'll gladly accept a patch if you want to
230write something up!).  For more information about LLVM, check out:
231
232* `LLVM homepage <http://llvm.org/>`_
233* `LLVM doxygen tree <http://llvm.org/doxygen/>`_
234
235