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 piece is the
16LLVM suite. This contains all of the tools, libraries, and header files needed
17to use LLVM. It contains an assembler, disassembler, bitcode analyzer and
18bitcode optimizer. It also contains basic regression tests that can be used to
19test the LLVM tools and the Clang front end.
20
21The second piece is the `Clang <http://clang.llvm.org/>`_ front end.  This
22component compiles C, C++, Objective C, and Objective C++ code into LLVM
23bitcode. Clang typically uses LLVM libraries to optimize the bitcode and emit
24machine code. LLVM fully supports the COFF object file format, which is
25compatible with all other existing Windows toolchains.
26
27The last major part of LLVM, the execution Test Suite, does not run on Windows,
28and this document does not discuss it.
29
30Additional information about the LLVM directory structure and tool chain
31can be found on the main :doc:`GettingStarted` page.
32
33
34Requirements
35============
36Before you begin to use the LLVM system, review the requirements given
37below.  This may save you some trouble by knowing ahead of time what hardware
38and software you will need.
39
40Hardware
41--------
42Any system that can adequately run Visual Studio 2013 is fine. The LLVM
43source tree and object files, libraries and executables will consume
44approximately 3GB.
45
46Software
47--------
48You will need Visual Studio 2013 or higher.
49
50You will also need the `CMake <http://www.cmake.org/>`_ build system since it
51generates the project files you will use to build with.
52
53If you would like to run the LLVM tests you will need `Python
54<http://www.python.org/>`_. Version 2.7 and newer are known to work. You will
55need `GnuWin32 <http://gnuwin32.sourceforge.net/>`_ tools, too.
56
57Do not install the LLVM directory tree into a path containing spaces (e.g.
58``C:\Documents and Settings\...``) as the configure step will fail.
59
60
61Getting Started
62===============
63Here's the short story for getting up and running quickly with LLVM:
64
651. Read the documentation.
662. Seriously, read the documentation.
673. Remember that you were warned twice about reading the documentation.
684. Get the Source Code
69
70   * With the distributed files:
71
72      1. ``cd <where-you-want-llvm-to-live>``
73      2. ``gunzip --stdout llvm-VERSION.tar.gz | tar -xvf -``
74         (*or use WinZip*)
75      3. ``cd llvm``
76
77   * With anonymous Subversion access:
78
79      1. ``cd <where-you-want-llvm-to-live>``
80      2. ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
81      3. ``cd llvm``
82
835. Use `CMake <http://www.cmake.org/>`_ to generate up-to-date project files:
84
85   * Once CMake is installed then the simplest way is to just start the
86     CMake GUI, select the directory where you have LLVM extracted to, and
87     the default options should all be fine.  One option you may really
88     want to change, regardless of anything else, might be the
89     ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
90     once compiling is complete, although installation is not mandatory for
91     using LLVM.  Another important option is ``LLVM_TARGETS_TO_BUILD``,
92     which controls the LLVM target architectures that are included on the
93     build.
94   * See the :doc:`LLVM CMake guide <CMake>` for detailed information about
95     how to configure the LLVM build.
96   * CMake generates project files for all build types. To select a specific
97     build type, use the Configuration manager from the VS IDE or the
98     ``/property:Configuration`` command line option when using MSBuild.
99
1006. Start Visual Studio
101
102   * In the directory you created the project files will have an ``llvm.sln``
103     file, just double-click on that to open Visual Studio.
104
1057. Build the LLVM Suite:
106
107   * The projects may still be built individually, but to build them all do
108     not just select all of them in batch build (as some are meant as
109     configuration projects), but rather select and build just the
110     ``ALL_BUILD`` project to build everything, or the ``INSTALL`` project,
111     which first builds the ``ALL_BUILD`` project, then installs the LLVM
112     headers, libs, and other useful things to the directory set by the
113     ``CMAKE_INSTALL_PREFIX`` setting when you first configured CMake.
114   * The Fibonacci project is a sample program that uses the JIT. Modify the
115     project's debugging properties to provide a numeric command line argument
116     or run it from the command line.  The program will print the
117     corresponding fibonacci value.
118
1198. Test LLVM in Visual Studio:
120
121   * If ``%PATH%`` does not contain GnuWin32, you may specify
122     ``LLVM_LIT_TOOLS_DIR`` on CMake for the path to GnuWin32.
123   * You can run LLVM tests by merely building the project "check". The test
124     results will be shown in the VS output window.
125
1269. Test LLVM on the command line:
127
128   * The LLVM tests can be run by changing directory to the llvm source
129     directory and running:
130
131     .. code-block:: bat
132
133        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
134
135     This example assumes that Python is in your PATH variable, you
136     have built a Win32 Debug version of llvm with a standard out of
137     line build. You should not see any unexpected failures, but will
138     see many unsupported tests and expected failures.
139
140     A specific test or test directory can be run with:
141
142     .. code-block:: bat
143
144        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
145
146
147An Example Using the LLVM Tool Chain
148====================================
149
1501. First, create a simple C file, name it '``hello.c``':
151
152   .. code-block:: c
153
154      #include <stdio.h>
155      int main() {
156        printf("hello world\n");
157        return 0;
158      }
159
1602. Next, compile the C file into an LLVM bitcode file:
161
162   .. code-block:: bat
163
164      C:\..> clang -c hello.c -emit-llvm -o hello.bc
165
166   This will create the result file ``hello.bc`` which is the LLVM bitcode
167   that corresponds the compiled program and the library facilities that
168   it required.  You can execute this file directly using ``lli`` tool,
169   compile it to native assembly with the ``llc``, optimize or analyze it
170   further with the ``opt`` tool, etc.
171
172   Alternatively you can directly output an executable with clang with:
173
174   .. code-block:: bat
175
176      C:\..> clang hello.c -o hello.exe
177
178   The ``-o hello.exe`` is required because clang currently outputs ``a.out``
179   when neither ``-o`` nor ``-c`` are given.
180
1813. Run the program using the just-in-time compiler:
182
183   .. code-block:: bat
184
185      C:\..> lli hello.bc
186
1874. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
188
189   .. code-block:: bat
190
191      C:\..> llvm-dis < hello.bc | more
192
1935. Compile the program to object code using the LLC code generator:
194
195   .. code-block:: bat
196
197      C:\..> llc -filetype=obj hello.bc
198
1996. Link to binary using Microsoft link:
200
201   .. code-block:: bat
202
203      C:\..> link hello.obj -defaultlib:libcmt
204
2057. Execute the native code program:
206
207   .. code-block:: bat
208
209      C:\..> hello.exe
210
211
212Common Problems
213===============
214If you are having problems building or using LLVM, or if you have any other
215general questions about LLVM, please consult the :doc:`Frequently Asked Questions
216<FAQ>` page.
217
218
219Links
220=====
221This document is just an **introduction** to how to use LLVM to do some simple
222things... there are many more interesting and complicated things that you can
223do that aren't documented here (but we'll gladly accept a patch if you want to
224write something up!).  For more information about LLVM, check out:
225
226* `LLVM homepage <http://llvm.org/>`_
227* `LLVM doxygen tree <http://llvm.org/doxygen/>`_
228
229