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, with the latest Update installed.
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. CMake 2.8.12.2 is the
52minimum required version for building with Visual Studio, though the latest
53version of CMake is recommended.
54
55If you would like to run the LLVM tests you will need `Python
56<http://www.python.org/>`_. Version 2.7 and newer are known to work. You will
57need `GnuWin32 <http://gnuwin32.sourceforge.net/>`_ tools, too.
58
59Do not install the LLVM directory tree into a path containing spaces (e.g.
60``C:\Documents and Settings\...``) as the configure step will fail.
61
62
63Getting Started
64===============
65Here's the short story for getting up and running quickly with LLVM:
66
671. Read the documentation.
682. Seriously, read the documentation.
693. Remember that you were warned twice about reading the documentation.
704. Get the Source Code
71
72   * With the distributed files:
73
74      1. ``cd <where-you-want-llvm-to-live>``
75      2. ``gunzip --stdout llvm-VERSION.tar.gz | tar -xvf -``
76         (*or use WinZip*)
77      3. ``cd llvm``
78
79   * With anonymous Subversion access:
80
81      1. ``cd <where-you-want-llvm-to-live>``
82      2. ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
83      3. ``cd llvm``
84
855. Use `CMake <http://www.cmake.org/>`_ to generate up-to-date project files:
86
87   * Once CMake is installed then the simplest way is to just start the
88     CMake GUI, select the directory where you have LLVM extracted to, and
89     the default options should all be fine.  One option you may really
90     want to change, regardless of anything else, might be the
91     ``CMAKE_INSTALL_PREFIX`` setting to select a directory to INSTALL to
92     once compiling is complete, although installation is not mandatory for
93     using LLVM.  Another important option is ``LLVM_TARGETS_TO_BUILD``,
94     which controls the LLVM target architectures that are included on the
95     build.
96   * If CMake complains that it cannot find the compiler, make sure that
97     you have the Visual Studio C++ Tools installed, not just Visual Studio
98     itself (trying to create a C++ project in Visual Studio will generally
99     download the C++ tools if they haven't already been).
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