docs/Projects.html - platform/external/llvm - Gitiles

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 <head>
   <title>Creating an LLVM Project</title>
   <link rel="stylesheet" href="llvm.css" type="text/css">
 </head>
 <body>

 <div class="doc_title">Creating an LLVM Project</div>

 <ol>
 <li><a href="#overview">Overview</a></li>
 <li><a href="#create">Create a project from the Sample Project</a></li>
 <li><a href="#source">Source tree layout</a></li>
 <li><a href="#makefiles">Writing LLVM-style Makefiles</a>
   <ol>
   <li><a href="#reqVars">Required Variables</a></li>
   <li><a href="#varsBuildDir">Variables for Building Subdirectories</a></li>
   <li><a href="#varsBuildLib">Variables for Building Libraries</a></li>
   <li><a href="#varsBuildProg">Variables for Building Programs</a></li>
   <li><a href="#miscVars">Miscellaneous Variables</a></li>
   </ol></li>
 <li><a href="#objcode">Placement of object code</a></li>
 <li><a href="#help">Further help</a></li>
 </ol>

 <div class="doc_author">
   <p>Written by John Criswell</p>
 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section"><a name="overview">Overview</a></div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>The LLVM build system is designed to facilitate the building of third party
 projects that use LLVM header files, libraries, and tools.  In order to use
 these facilities, a Makefile from a project must do the following things:</p>

 <ol>
   <li>Set <tt>make</tt> variables. There are several variables that a Makefile
   needs to set to use the LLVM build system:
   <ul>
     <li><tt>PROJECT_NAME</tt> - The name by which your project is known.</li>
     <li><tt>LLVM_SRC_ROOT</tt> - The root of the LLVM source tree.</li>
     <li><tt>LLVM_OBJ_ROOT</tt> - The root of the LLVM object tree.</li>
     <li><tt>PROJ_SRC_ROOT</tt> - The root of the project's source tree.</li>
     <li><tt>PROJ_OBJ_ROOT</tt> - The root of the project's object tree.</li>
     <li><tt>PROJ_INSTALL_ROOT</tt> - The root installation directory.</li>
     <li><tt>LEVEL</tt> - The relative path from the current directory to the
     project's root ($PROJ_OBJ_ROOT).</li>
   </ul></li>
   <li>Include <tt>Makefile.config</tt> from <tt>$(LLVM_OBJ_ROOT)</tt>.</li>
   <li>Include <tt>Makefile.rules</tt> from <tt>$(LLVM_SRC_ROOT)</tt>.</li>
 </ol>

 <p>There are two ways that you can set all of these variables:</p>
 <ol>
   <li>You can write your own Makefiles which hard-code these values.</li>
   <li>You can use the pre-made LLVM sample project. This sample project
   includes Makefiles, a configure script that can be used to configure the
   location of LLVM, and the ability to support multiple object directories
   from a single source directory.</li>
 </ol>

 <p>This document assumes that you will base your project on the LLVM sample
 project found in <tt>llvm/projects/sample</tt>.  If you want to devise your own
 build system, studying the sample project and LLVM Makefiles will probably
 provide enough information on how to write your own Makefiles.</p>

 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section">
   <a name="create">Create a Project from the Sample Project</a>
 </div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>Follow these simple steps to start your project:</p>

 <ol>
 <li>Copy the <tt>llvm/projects/sample</tt> directory to any place of your
 choosing.  You can place it anywhere you like.  Rename the directory to match
 the name of your project.</li>

 <li>
 If you downloaded LLVM using CVS, remove all the directories named CVS (and all
 the files therein) from your project's new source tree.  This will keep CVS
 from thinking that your project is inside <tt>llvm/projects/sample</tt>.
 </li>

 <li>Add your source code and Makefiles to your source tree.</li>

 <li>If you want your project to be configured with the <tt>configure</tt> script
 then you need to edit <tt>autoconf/configure.ac</tt> as follows:
   <ul>
     <li><b>AC_INIT</b>. Place the name of your project, its version number and
     a contact email address for your project as the arguments to this macro</li>
     <li><b>AC_CONFIG_AUC_DIR</b>. If your project isn't in the
     <tt>llvm/projects</tt> directory then you might need to adjust this so that
     it specifies a relative path to the <tt>llvm/autoconf</tt> directory.</li>
     <li><b>LLVM_CONFIG_PROJECT</b>. Just leave this alone.</li>
     <li><b>AC_CONFIG_SRCDIR</b>. Specify a path to a file name that identifies
     your project; or just leave it at <tt>Makefile.config.in</tt></li>
     <li><b>AC_CONFIG_FILES</b>. Do not change.</li>
     <li><b>AC_CONFIG_MAKEFILE</b>. Use one of these macros for each Makefile
     that your project uses. This macro arranges for your makefiles to be copied
     from the source directory, unmodified, to the build directory.</li>
   </ul>
 </li>

 <li>After updating <tt>autoconf/configure.ac</tt>, regenerate the
 configure script with these commands:

 <div class="doc_code">
 <p><tt>% cd autoconf<br>
        % AutoRegen.sh</tt></p>
 </div>

 <p>You must be using Autoconf version 2.59 or later and your aclocal version
 should 1.9 or later.</p></li>

 <li>Run <tt>configure</tt> in the directory in which you want to place
 object code.  Use the following options to tell your project where it
 can find LLVM:

   <dl>
     <dt><tt>--with-llvmsrc=&lt;directory&gt;</tt></dt>
     <dd>Tell your project where the LLVM source tree is located.</dd>
     <dt><br/><tt>--with-llvmobj=&lt;directory&gt;</tt></dt>
     <dd>Tell your project where the LLVM object tree is located.</dd>
     <dt><br/><tt>--prefix=&lt;directory&gt;</tt></dt>
     <dd>Tell your project where it should get installed.</dd>
   </dl>
 </ol>

 <p>That's it!  Now all you have to do is type <tt>gmake</tt> (or <tt>make</tt>
 if your on a GNU/Linux system) in the root of your object directory, and your
 project should build.</p>

 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section">
   <a name="source">Source Tree Layout</a>
 </div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>In order to use the LLVM build system, you will want to organize your
 source code so that it can benefit from the build system's features.
 Mainly, you want your source tree layout to look similar to the LLVM
 source tree layout.  The best way to do this is to just copy the
 project tree from <tt>llvm/projects/sample</tt> and modify it to meet
 your needs, but you can certainly add to it if you want.</p>

 <p>Underneath your top level directory, you should have the following
 directories:</p>

 <dl>
   <dt><b>lib</b>
   <dd>
   This subdirectory should contain all of your library source
   code.  For each library that you build, you will have one
   directory in <b>lib</b> that will contain that library's source
   code.

   <p>
   Libraries can be object files, archives, or dynamic libraries.
   The <b>lib</b> directory is just a convenient place for libraries
   as it places them all in a directory from which they can be linked
   later.

   <dt><b>include</b>
   <dd>
   This subdirectory should contain any header files that are
   global to your project.  By global, we mean that they are used
   by more than one library or executable of your project.
   <p>
   By placing your header files in <b>include</b>, they will be
   found automatically by the LLVM build system.  For example, if
   you have a file <b>include/jazz/note.h</b>, then your source
   files can include it simply with <b>#include "jazz/note.h"</b>.

   <dt><b>tools</b>
   <dd>
   This subdirectory should contain all of your source
   code for executables.  For each program that you build, you
   will have one directory in <b>tools</b> that will contain that
   program's source code.
   <p>

   <dt><b>test</b>
   <dd>
   This subdirectory should contain tests that verify that your code
   works correctly.  Automated tests are especially useful.
   <p>
   Currently, the LLVM build system provides basic support for tests.
   The LLVM system provides the following:
   <ul>
     <li>
     LLVM provides a tcl procedure that is used by Dejagnu to run
     tests.  It can be found in <tt>llvm/lib/llvm-dg.exp</tt>.  This
     test procedure uses RUN lines in the actual test case to determine
     how to run the test.  See the <a
     href="TestingGuide.html">TestingGuide</a> for more details. You
     can easily write Makefile support similar to the Makefiles in
     <tt>llvm/test</tt> to use Dejagnu to run your project's tests.<br/></li>
     <li>
     LLVM contains an optional package called <tt>llvm-test</tt>
     which provides benchmarks and programs that are known to compile with the
     LLVM GCC front ends.  You can use these
     programs to test your code, gather statistics information, and
     compare it to the current LLVM performance statistics.
     <br/>Currently, there is no way to hook your tests directly into the
     <tt>llvm/test</tt> testing harness.  You will simply
     need to find a way to use the source provided within that directory
     on your own.
   </ul>
 </dl>

 <p>Typically, you will want to build your <b>lib</b> directory first followed by
 your <b>tools</b> directory.</p>

 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section">
   <a name="makefiles">Writing LLVM Style Makefiles</a>
 </div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>The LLVM build system provides a convenient way to build libraries and
 executables.  Most of your project Makefiles will only need to define a few
 variables.  Below is a list of the variables one can set and what they can
 do:</p>

 </div>

 <!-- ======================================================================= -->
 <div class="doc_subsection">
   <a name="reqVars">Required Variables</a>
 </div>

 <div class="doc_text">

 <dl>
   <dt>LEVEL
   <dd>
   This variable is the relative path from this Makefile to the
   top directory of your project's source code.  For example, if
   your source code is in <tt>/tmp/src</tt>, then the Makefile in
   <tt>/tmp/src/jump/high</tt> would set <tt>LEVEL</tt> to <tt>"../.."</tt>.
 </dl>

 </div>

 <!-- ======================================================================= -->
 <div class="doc_subsection">
   <a name="varsBuildDir">Variables for Building Subdirectories</a>
 </div>

 <div class="doc_text">

 <dl>
   <dt>DIRS
   <dd>
   This is a space separated list of subdirectories that should be
   built.  They will be built, one at a time, in the order
   specified.
   <p>

   <dt>PARALLEL_DIRS
   <dd>
   This is a list of directories that can be built in parallel.
   These will be built after the directories in DIRS have been
   built.
   <p>

   <dt>OPTIONAL_DIRS
   <dd>
   This is a list of directories that can be built if they exist,
   but will not cause an error if they do not exist.  They are
   built serially in the order in which they are listed.
 </dl>

 </div>

 <!-- ======================================================================= -->
 <div class="doc_subsection">
   <a name="varsBuildLib">Variables for Building Libraries</a>
 </div>

 <div class="doc_text">

 <dl>
   <dt>LIBRARYNAME
   <dd>
   This variable contains the base name of the library that will
   be built.  For example, to build a library named
   <tt>libsample.a</tt>, LIBRARYNAME should be set to
   <tt>sample</tt>.
   <p>

   <dt>BUILD_ARCHIVE
   <dd>
   By default, a library is a <tt>.o</tt> file that is linked
   directly into a program.  To build an archive (also known as
   a static library), set the BUILD_ARCHIVE variable.
   <p>

   <dt>SHARED_LIBRARY
   <dd>
   If SHARED_LIBRARY is defined in your Makefile, a shared
   (or dynamic) library will be built.
 </dl>

 </div>

 <!-- ======================================================================= -->
 <div class="doc_subsection">
   <a name="varsBuildProg">Variables for Building Programs</a>
 </div>

 <div class="doc_text">

 <dl>
   <dt>TOOLNAME
   <dd>
   This variable contains the name of the program that will
   be built.  For example, to build an executable named
   <tt>sample</tt>, TOOLNAME should be set to <tt>sample</tt>.
   <p>

   <dt>USEDLIBS
   <dd>
   This variable holds a space separated list of libraries that
   should be linked into the program.  These libraries must either
   be LLVM libraries or libraries that come from your <b>lib</b>
   directory.  The libraries must be specified by their base name.
   For example, to link libsample.a, you would set USEDLIBS to
   <tt>sample</tt>.
   <p>
   Note that this works only for statically linked libraries.
   <p>

   <dt>LIBS
   <dd>
   To link dynamic libraries, add <tt>-l&lt;library base name&gt;</tt> to
   the LIBS variable.  The LLVM build system will look in the same places
   for dynamic libraries as it does for static libraries.
   <p>
   For example, to link <tt>libsample.so</tt>, you would have the
   following line in your <tt>Makefile</tt>:
   <p>
   <tt>
   LIBS += -lsample
   </tt>
 </dl>

 </div>

 <!-- ======================================================================= -->
 <div class="doc_subsection">
   <a name="miscVars">Miscellaneous Variables</a>
 </div>

 <div class="doc_text">

 <dl>
   <dt>ExtraSource
   <dd>
   This variable contains a space separated list of extra source
   files that need to be built.  It is useful for including the
   output of Lex and Yacc programs.
   <p>

   <dt>CFLAGS
   <dt>CPPFLAGS
   <dd>
   This variable can be used to add options to the C and C++
   compiler, respectively.  It is typically used to add options
   that tell the compiler the location of additional directories
   to search for header files.
   <p>
   It is highly suggested that you append to CFLAGS and CPPFLAGS as
   opposed to overwriting them.  The master Makefiles may already
   have useful options in them that you may not want to overwrite.
   <p>
 </dl>

 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section">
   <a name="objcode">Placement of Object Code</a>
 </div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>The final location of built libraries and executables will depend upon
 whether you do a Debug, Release, or Profile build.</p>

 <dl>
   <dt>Libraries
   <dd>
   All libraries (static and dynamic) will be stored in
   <tt>PROJ_OBJ_ROOT/&lt;type&gt;/lib</tt>, where type is <tt>Debug</tt>,
   <tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or
   profiled build, respectively.<p>

   <dt>Executables
   <dd>All executables will be stored in
   <tt>PROJ_OBJ_ROOT/&lt;type&gt;/bin</tt>, where type is <tt>Debug</tt>,
   <tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or profiled
   build, respectively.
 </dl>

 </div>

 <!-- *********************************************************************** -->
 <div class="doc_section">
   <a name="help">Further Help</a>
 </div>
 <!-- *********************************************************************** -->

 <div class="doc_text">

 <p>If you have any questions or need any help creating an LLVM project,
 the LLVM team would be more than happy to help.  You can always post your
 questions to the <a
 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developers
 Mailing List</a>.</p>

 </div>

 <!-- *********************************************************************** -->
 <hr>
 <address>
   <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
   src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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   src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>

   <a href="mailto:criswell@uiuc.edu">John Criswell</a><br>
   <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
   <br>
   Last modified: $Date$
 </address>

 </body>
 </html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
	"http://www.w3.org/TR/html4/strict.dtd">
	<html>
	<head>
	<title>Creating an LLVM Project</title>
	<link rel="stylesheet" href="llvm.css" type="text/css">
	</head>
	<body>

	<div class="doc_title">Creating an LLVM Project</div>

	<ol>
	<li><a href="#overview">Overview</a></li>
	<li><a href="#create">Create a project from the Sample Project</a></li>
	<li><a href="#source">Source tree layout</a></li>
	<li><a href="#makefiles">Writing LLVM-style Makefiles</a>
	<ol>
	<li><a href="#reqVars">Required Variables</a></li>
	<li><a href="#varsBuildDir">Variables for Building Subdirectories</a></li>
	<li><a href="#varsBuildLib">Variables for Building Libraries</a></li>
	<li><a href="#varsBuildProg">Variables for Building Programs</a></li>
	<li><a href="#miscVars">Miscellaneous Variables</a></li>
	</ol></li>
	<li><a href="#objcode">Placement of object code</a></li>
	<li><a href="#help">Further help</a></li>
	</ol>

	<div class="doc_author">
	<p>Written by John Criswell</p>
	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section"><a name="overview">Overview</a></div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>The LLVM build system is designed to facilitate the building of third party
	projects that use LLVM header files, libraries, and tools. In order to use
	these facilities, a Makefile from a project must do the following things:</p>

	<ol>
	<li>Set <tt>make</tt> variables. There are several variables that a Makefile
	needs to set to use the LLVM build system:
	<ul>
	<li><tt>PROJECT_NAME</tt> - The name by which your project is known.</li>
	<li><tt>LLVM_SRC_ROOT</tt> - The root of the LLVM source tree.</li>
	<li><tt>LLVM_OBJ_ROOT</tt> - The root of the LLVM object tree.</li>
	<li><tt>PROJ_SRC_ROOT</tt> - The root of the project's source tree.</li>
	<li><tt>PROJ_OBJ_ROOT</tt> - The root of the project's object tree.</li>
	<li><tt>PROJ_INSTALL_ROOT</tt> - The root installation directory.</li>
	<li><tt>LEVEL</tt> - The relative path from the current directory to the
	project's root ($PROJ_OBJ_ROOT).</li>
	</ul></li>
	<li>Include <tt>Makefile.config</tt> from <tt>$(LLVM_OBJ_ROOT)</tt>.</li>
	<li>Include <tt>Makefile.rules</tt> from <tt>$(LLVM_SRC_ROOT)</tt>.</li>
	</ol>

	<p>There are two ways that you can set all of these variables:</p>
	<ol>
	<li>You can write your own Makefiles which hard-code these values.</li>
	<li>You can use the pre-made LLVM sample project. This sample project
	includes Makefiles, a configure script that can be used to configure the
	location of LLVM, and the ability to support multiple object directories
	from a single source directory.</li>
	</ol>

	<p>This document assumes that you will base your project on the LLVM sample
	project found in <tt>llvm/projects/sample</tt>. If you want to devise your own
	build system, studying the sample project and LLVM Makefiles will probably
	provide enough information on how to write your own Makefiles.</p>

	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section">
	<a name="create">Create a Project from the Sample Project</a>
	</div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>Follow these simple steps to start your project:</p>

	<ol>
	<li>Copy the <tt>llvm/projects/sample</tt> directory to any place of your
	choosing. You can place it anywhere you like. Rename the directory to match
	the name of your project.</li>

	<li>
	If you downloaded LLVM using CVS, remove all the directories named CVS (and all
	the files therein) from your project's new source tree. This will keep CVS
	from thinking that your project is inside <tt>llvm/projects/sample</tt>.
	</li>

	<li>Add your source code and Makefiles to your source tree.</li>

	<li>If you want your project to be configured with the <tt>configure</tt> script
	then you need to edit <tt>autoconf/configure.ac</tt> as follows:
	<ul>
	<li><b>AC_INIT</b>. Place the name of your project, its version number and
	a contact email address for your project as the arguments to this macro</li>
	<li><b>AC_CONFIG_AUC_DIR</b>. If your project isn't in the
	<tt>llvm/projects</tt> directory then you might need to adjust this so that
	it specifies a relative path to the <tt>llvm/autoconf</tt> directory.</li>
	<li><b>LLVM_CONFIG_PROJECT</b>. Just leave this alone.</li>
	<li><b>AC_CONFIG_SRCDIR</b>. Specify a path to a file name that identifies
	your project; or just leave it at <tt>Makefile.config.in</tt></li>
	<li><b>AC_CONFIG_FILES</b>. Do not change.</li>
	<li><b>AC_CONFIG_MAKEFILE</b>. Use one of these macros for each Makefile
	that your project uses. This macro arranges for your makefiles to be copied
	from the source directory, unmodified, to the build directory.</li>
	</ul>
	</li>

	<li>After updating <tt>autoconf/configure.ac</tt>, regenerate the
	configure script with these commands:

	<div class="doc_code">
	<p><tt>% cd autoconf<br>
	% AutoRegen.sh</tt></p>
	</div>

	<p>You must be using Autoconf version 2.59 or later and your aclocal version
	should 1.9 or later.</p></li>

	<li>Run <tt>configure</tt> in the directory in which you want to place
	object code. Use the following options to tell your project where it
	can find LLVM:

	<dl>
	<dt><tt>--with-llvmsrc=<directory></tt></dt>
	<dd>Tell your project where the LLVM source tree is located.</dd>
	<dt><br/><tt>--with-llvmobj=<directory></tt></dt>
	<dd>Tell your project where the LLVM object tree is located.</dd>
	<dt><br/><tt>--prefix=<directory></tt></dt>
	<dd>Tell your project where it should get installed.</dd>
	</dl>
	</ol>

	<p>That's it! Now all you have to do is type <tt>gmake</tt> (or <tt>make</tt>
	if your on a GNU/Linux system) in the root of your object directory, and your
	project should build.</p>

	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section">
	<a name="source">Source Tree Layout</a>
	</div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>In order to use the LLVM build system, you will want to organize your
	source code so that it can benefit from the build system's features.
	Mainly, you want your source tree layout to look similar to the LLVM
	source tree layout. The best way to do this is to just copy the
	project tree from <tt>llvm/projects/sample</tt> and modify it to meet
	your needs, but you can certainly add to it if you want.</p>

	<p>Underneath your top level directory, you should have the following
	directories:</p>

	<dl>
	<dt><b>lib</b>
	<dd>
	This subdirectory should contain all of your library source
	code. For each library that you build, you will have one
	directory in <b>lib</b> that will contain that library's source
	code.

	<p>
	Libraries can be object files, archives, or dynamic libraries.
	The <b>lib</b> directory is just a convenient place for libraries
	as it places them all in a directory from which they can be linked
	later.

	<dt><b>include</b>
	<dd>
	This subdirectory should contain any header files that are
	global to your project. By global, we mean that they are used
	by more than one library or executable of your project.
	<p>
	By placing your header files in <b>include</b>, they will be
	found automatically by the LLVM build system. For example, if
	you have a file <b>include/jazz/note.h</b>, then your source
	files can include it simply with <b>#include "jazz/note.h"</b>.

	<dt><b>tools</b>
	<dd>
	This subdirectory should contain all of your source
	code for executables. For each program that you build, you
	will have one directory in <b>tools</b> that will contain that
	program's source code.
	<p>

	<dt><b>test</b>
	<dd>
	This subdirectory should contain tests that verify that your code
	works correctly. Automated tests are especially useful.
	<p>
	Currently, the LLVM build system provides basic support for tests.
	The LLVM system provides the following:
	<ul>
	<li>
	LLVM provides a tcl procedure that is used by Dejagnu to run
	tests. It can be found in <tt>llvm/lib/llvm-dg.exp</tt>. This
	test procedure uses RUN lines in the actual test case to determine
	how to run the test. See the <a
	href="TestingGuide.html">TestingGuide</a> for more details. You
	can easily write Makefile support similar to the Makefiles in
	<tt>llvm/test</tt> to use Dejagnu to run your project's tests.<br/></li>
	<li>
	LLVM contains an optional package called <tt>llvm-test</tt>
	which provides benchmarks and programs that are known to compile with the
	LLVM GCC front ends. You can use these
	programs to test your code, gather statistics information, and
	compare it to the current LLVM performance statistics.
	<br/>Currently, there is no way to hook your tests directly into the
	<tt>llvm/test</tt> testing harness. You will simply
	need to find a way to use the source provided within that directory
	on your own.
	</ul>
	</dl>

	<p>Typically, you will want to build your <b>lib</b> directory first followed by
	your <b>tools</b> directory.</p>

	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section">
	<a name="makefiles">Writing LLVM Style Makefiles</a>
	</div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>The LLVM build system provides a convenient way to build libraries and
	executables. Most of your project Makefiles will only need to define a few
	variables. Below is a list of the variables one can set and what they can
	do:</p>

	</div>

	<!-- ======================================================================= -->
	<div class="doc_subsection">
	<a name="reqVars">Required Variables</a>
	</div>

	<div class="doc_text">

	<dl>
	<dt>LEVEL
	<dd>
	This variable is the relative path from this Makefile to the
	top directory of your project's source code. For example, if
	your source code is in <tt>/tmp/src</tt>, then the Makefile in
	<tt>/tmp/src/jump/high</tt> would set <tt>LEVEL</tt> to <tt>"../.."</tt>.
	</dl>

	</div>

	<!-- ======================================================================= -->
	<div class="doc_subsection">
	<a name="varsBuildDir">Variables for Building Subdirectories</a>
	</div>

	<div class="doc_text">

	<dl>
	<dt>DIRS
	<dd>
	This is a space separated list of subdirectories that should be
	built. They will be built, one at a time, in the order
	specified.
	<p>

	<dt>PARALLEL_DIRS
	<dd>
	This is a list of directories that can be built in parallel.
	These will be built after the directories in DIRS have been
	built.
	<p>

	<dt>OPTIONAL_DIRS
	<dd>
	This is a list of directories that can be built if they exist,
	but will not cause an error if they do not exist. They are
	built serially in the order in which they are listed.
	</dl>

	</div>

	<!-- ======================================================================= -->
	<div class="doc_subsection">
	<a name="varsBuildLib">Variables for Building Libraries</a>
	</div>

	<div class="doc_text">

	<dl>
	<dt>LIBRARYNAME
	<dd>
	This variable contains the base name of the library that will
	be built. For example, to build a library named
	<tt>libsample.a</tt>, LIBRARYNAME should be set to
	<tt>sample</tt>.
	<p>

	<dt>BUILD_ARCHIVE
	<dd>
	By default, a library is a <tt>.o</tt> file that is linked
	directly into a program. To build an archive (also known as
	a static library), set the BUILD_ARCHIVE variable.
	<p>

	<dt>SHARED_LIBRARY
	<dd>
	If SHARED_LIBRARY is defined in your Makefile, a shared
	(or dynamic) library will be built.
	</dl>

	</div>

	<!-- ======================================================================= -->
	<div class="doc_subsection">
	<a name="varsBuildProg">Variables for Building Programs</a>
	</div>

	<div class="doc_text">

	<dl>
	<dt>TOOLNAME
	<dd>
	This variable contains the name of the program that will
	be built. For example, to build an executable named
	<tt>sample</tt>, TOOLNAME should be set to <tt>sample</tt>.
	<p>

	<dt>USEDLIBS
	<dd>
	This variable holds a space separated list of libraries that
	should be linked into the program. These libraries must either
	be LLVM libraries or libraries that come from your <b>lib</b>
	directory. The libraries must be specified by their base name.
	For example, to link libsample.a, you would set USEDLIBS to
	<tt>sample</tt>.
	<p>
	Note that this works only for statically linked libraries.
	<p>

	<dt>LIBS
	<dd>
	To link dynamic libraries, add <tt>-l<library base name></tt> to
	the LIBS variable. The LLVM build system will look in the same places
	for dynamic libraries as it does for static libraries.
	<p>
	For example, to link <tt>libsample.so</tt>, you would have the
	following line in your <tt>Makefile</tt>:
	<p>
	<tt>
	LIBS += -lsample
	</tt>
	</dl>

	</div>

	<!-- ======================================================================= -->
	<div class="doc_subsection">
	<a name="miscVars">Miscellaneous Variables</a>
	</div>

	<div class="doc_text">

	<dl>
	<dt>ExtraSource
	<dd>
	This variable contains a space separated list of extra source
	files that need to be built. It is useful for including the
	output of Lex and Yacc programs.
	<p>

	<dt>CFLAGS
	<dt>CPPFLAGS
	<dd>
	This variable can be used to add options to the C and C++
	compiler, respectively. It is typically used to add options
	that tell the compiler the location of additional directories
	to search for header files.
	<p>
	It is highly suggested that you append to CFLAGS and CPPFLAGS as
	opposed to overwriting them. The master Makefiles may already
	have useful options in them that you may not want to overwrite.
	<p>
	</dl>

	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section">
	<a name="objcode">Placement of Object Code</a>
	</div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>The final location of built libraries and executables will depend upon
	whether you do a Debug, Release, or Profile build.</p>

	<dl>
	<dt>Libraries
	<dd>
	All libraries (static and dynamic) will be stored in
	<tt>PROJ_OBJ_ROOT/<type>/lib</tt>, where type is <tt>Debug</tt>,
	<tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or
	profiled build, respectively.<p>

	<dt>Executables
	<dd>All executables will be stored in
	<tt>PROJ_OBJ_ROOT/<type>/bin</tt>, where type is <tt>Debug</tt>,
	<tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or profiled
	build, respectively.
	</dl>

	</div>

	<!-- *********************************************************************** -->
	<div class="doc_section">
	<a name="help">Further Help</a>
	</div>
	<!-- *********************************************************************** -->

	<div class="doc_text">

	<p>If you have any questions or need any help creating an LLVM project,
	the LLVM team would be more than happy to help. You can always post your
	questions to the <a
	href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developers
	Mailing List</a>.</p>

	</div>

	<!-- *********************************************************************** -->
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