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<head>

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<title>Getting Started with LLVM System</title>

</head>

<center><h1>Getting Started with the LLVM System By: <a

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href="mailto:gshi1@uiuc.edu">Guochun Shi</a>,

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<a href="mailto:sabre@nondot.org">Chris Lattner</a>,

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<a href="mailto:criswell@uiuc.edu">John Criswell</a>,

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<a href="http://misha.brukman.net">Misha Brukman</a>, and

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<a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>

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</h1></center>

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<h2><a name="Contents">Contents</a></h2>

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<ul>

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<li><a href="#overview">Overview</a>

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<ol>

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<li><a href="#requirements">Requirements</a>

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<ol>

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<li><a href="#hardware">Hardware</a>

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<li><a href="#software">Software</a>

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</ol>

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</ol>

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<li><a href="#quickstart">Getting Started Quickly (A Summary)</a>

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<li><a href="#starting">Getting started with LLVM</a>

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<ol>

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<li><a href="#terminology">Terminology and Notation</tt></a>

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<li><a href="#environment">Setting Up Your Environment</a>

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<li><a href="#unpack">Unpacking the LLVM Archives</a>

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<li><a href="#checkout">Checkout LLVM from CVS</a>

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<li><a href="#installcf">Install the C Front End</a>

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<li><a href="#config">Local LLVM Configuration</tt></a>

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<li><a href="#compile">Compiling the LLVM Suite Source Code</a>

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<li><a href="#objfiles">The Location of LLVM Object Files</tt></a>

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</ol>

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<li><a href="#layout">Program layout</a>

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<ol>

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<li><a href="#cvsdir"><tt>CVS</tt> directories</a>

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<li><a href="#include"><tt>llvm/include</tt></a>

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<li><a href="#tools"><tt>llvm/tools</tt></a>

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<li><a href="#utils"><tt>llvm/utils</tt></a>

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</ol>

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<li><a href="#cfront">Compiling the LLVM GCC Front End</a>

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<li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>

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<li><a href="#problems">Common Problems</a>

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<li><a href="#links">Links</a>

</ul>

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<h2><a name="overview">Overview</a></h2>

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</center>

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<hr>

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Welcome to LLVM! In order to get started, you first need to know some

basic information.

First, LLVM comes in two pieces. The first piece is the LLVM suite. This

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contains all of the tools, libraries, and header files needed to use the

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low level virtual machine. It also contains a test suite that can be used

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to test the LLVM tools and the GCC front end.

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The second piece is the GCC front end. This component provides a version

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of GCC that compiles C and C++ code into LLVM bytecode. Currently, the

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GCC front end is a modified version of GCC 3.4 (we track the GCC 3.4

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development). Once compiled into LLVM bytecode, a program can be

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manipulated with the LLVM tools from the LLVM suite.

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<h3><a name="requirements">Requirements</a></h3>

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Before you begin to use the LLVM system, review the requirements given

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below. This may save you some trouble by knowing ahead of time what

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hardware and software you will need.

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<h4><a name="hardware">Hardware</a></h4>

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LLVM is known to work on the following platforms:

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<ul>

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<li> Linux on x86

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<ul>

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<li> Approximately 760 MB of Free Disk Space

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<ul>

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<li>Source code: 30 MB

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<li>Object code: 670 MB

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<li>GCC front end: 60 MB

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</ul>

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</ul>

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<li> Solaris on SparcV9 (Ultrasparc)

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<ul>

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<li> Approximately 1.24 GB of Free Disk Space

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<ul>

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<li>Source code: 30 MB

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<li>Object code: 1000 MB

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<li>GCC front end: 210 MB

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</ul>

</ul>

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If you want to compile your own version of the GCC front end, you will need

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additional disk space:

<ul>

<li>Linux on x86

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<li> Approximately 249 MB of Free Disk Space

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<ul>

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<li>Source code: 146 MB

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<li>Object code: 82 MB

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<li>Installed binaries: 21 MB

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<li>Solaris on Sparc

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<li> Approximately 264 MB of Free Disk Space

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<ul>

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<li>Source code: 146 MB

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<li>Object code: 93 MB

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<li>Installed binaries: 25 MB

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</ul>

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LLVM may compile on other platforms. The LLVM utilities should work

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on other platforms, so it should be possible to generate and produce LLVM

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bytecode on unsupported platforms (although bytecode generated on one

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platform may not work on another platform). However, the code generators

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and Just-In-Time (JIT) compilers only generate SparcV9 or x86 machine code.

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<h4><a name="software">Software</a></h4>

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Unpacking the distribution requires the following tools:

<dt>GNU Zip (gzip)

<dt>GNU Tar

<dd>

These tools are needed to uncompress and unarchive the software.

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Regular Solaris <tt>tar</tt> may work for unpacking the TAR archive but

is untested.

</dl>

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Compiling LLVM requires that you have several different software packages

installed:

<dt> GCC

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The GNU Compiler Collection must be installed with C and C++ language

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support. GCC 3.2.x works, and GCC 3.x is generally supported.

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Note that we currently do not support any other C++ compiler.

<dt> GNU Make

<dd>

The LLVM build system relies upon GNU Make extensions. Therefore, you

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will need GNU Make (sometimes known as gmake) to build LLVM.

<dt> Flex and Bison

<dd>

The LLVM source code is built using flex and bison. You will not be

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able to configure and compile LLVM without them.

<dt> GNU M4

<dd>

If you are installing Bison on your machine for the first time, you

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will need GNU M4 (version 1.4 or higher).

</dl>

There are some additional tools that you may want to have when working with

LLVM:

<ul>

<li>GNU Autoconf

<li>GNU M4

If you want to make changes to the configure scripts, you will need

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GNU autoconf (2.53 or higher), and consequently, GNU M4 (version 1.4

or higher).

</ul>

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The remainder of this guide is meant to get you up and running with

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LLVM and to give you some basic information about the LLVM environment.

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The <a href"#quickstart">next section</a> gives a short summary for those

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who are already familiar with the system and want to get started as quickly

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as possible. A more complete description is provided after that.

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The later sections of this guide describe the <a

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href="#layout">general layout</a> of the the LLVM source-tree, a <a

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href="#tutorial">simple example</a> using the LLVM tool chain, and <a

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href="#links">links</a> to find more information about LLVM or to get

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help via e-mail.

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<h2><a name="quickstart">Getting Started Quickly (A Summary)</a></h2>

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</center>

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<hr>

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Here's the short story for getting up and running quickly with LLVM:

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<ol>

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<li>Install the GCC front end:

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<ol>

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<li><tt>cd where-you-want-the-C-front-end-to-live</tt>

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<li><tt>gunzip --stdout cfrontend.platform.tar.gz | tar -xvf

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-</tt>

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</ol>

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<li>Get the Source Code

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<ul>

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<li>With the distributed files:

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<li><tt>cd where-you-want-llvm-to-live</tt>

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<li><tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt>

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<li>With anonymous CVS access:

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<ol>

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<li>Find the path to the CVS repository containing LLVM (we'll

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call this CVSROOTDIR).

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<li><tt>cd where-you-want-llvm-to-live</tt>

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<li><tt>cvs -d CVSROOTDIR checkout llvm</tt>

</ol>

</ul>

</ul>

<li>Configure the LLVM Build Environment

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<ol>

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<li>Change directory to where you want to store the LLVM object

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files and run <tt>configure</tt> to configure the Makefiles and

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header files for the default platform.

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Useful options include:

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<ul>

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<li><tt>--with-llvmgccdir=directory</tt>

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Specify where the LLVM GCC frontend is installed.

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</ul>

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<li>Build the LLVM Suite

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<li>Set your LLVM_LIB_SEARCH_PATH environment variable.

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<li><tt>gmake -k |& tee gnumake.out

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# this is csh or tcsh syntax</tt>

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</ol>

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</ol>

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See <a href="#environment">Setting Up Your Environment</a> on tips to

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simplify working with the LLVM front-end and compiled tools. See the

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next section for other useful details in working with LLVM,

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or go straight to <a href="#layout">Program Layout</a> to learn about the

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layout of the source code tree. For information on building the GCC front

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end yourself, see <a href="#cfront">Compiling the LLVM GCC Front End</a> for

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information.

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<h2><a name="starting">Getting Started with LLVM</a></h2>

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</center>

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<hr>

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<h3><a name="terminology">Terminology and Notation</a></h3>

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Throughout this manual, the following names are used to denote paths

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specific to the local system and working environment. These are not

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environment variables you need to set but just strings used in the rest

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of this document below. In any of the examples below, simply replace

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each of these names with the appropriate pathname on your local system.

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All these paths are absolute:

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<dt>CVSROOTDIR

<dd>

This is the path for the CVS repository containing the LLVM source

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code. Ask the person responsible for your local LLVM installation to

give you this path.

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<dt>SRC_ROOT

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<dd>

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This is the top level directory of the LLVM source tree.

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<dt>OBJ_ROOT

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<dd>

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This is the top level directory of the LLVM object tree (i.e. the

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tree where object files and compiled programs will be placed. It

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can be the same as SRC_ROOT).

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<dt>LLVMGCCDIR

<dd>

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This is the where the LLVM GCC Front End is installed.

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For the pre-built GCC front end binaries, the LLVMGCCDIR is the

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<tt>cfrontend/platform/llvm-gcc</tt>.

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<dt>GCCSRC

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<dd>

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This is the location of the LLVM GCC front end source code (used

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only if the LLVM GCC front end is being compiled).

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<dt>GCCOBJ

<dd>

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This is the location of the LLVM GCC front end object code (used

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only if the LLVM GCC front end is being compiled). It can be

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safely removed once the LLVM GCC front end is built and installed.

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</dl>

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<h3><a name="environment">Setting Up Your Environment</a></h3>

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In order to compile and use LLVM, you will need to set some environment

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variables. There are also some shell aliases which you may find useful.

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You can set these on the command line, or better yet, set them in your

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<tt>.cshrc</tt> or <tt>.profile</tt>.

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<dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>LLVMGCCDIR/llvm-gcc/bytecode-libs</tt>

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<dd>

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This environment variable helps the LLVM GCC front end find bytecode

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libraries that it will need for compilation.

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<dt>alias llvmgcc LLVMGCCDIR<tt>/bin/llvm-gcc</tt>

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<dt>alias llvmg++ LLVMGCCDIR<tt>/bin/llvm-g++</tt>

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<dd>

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This alias allows you to use the LLVM C and C++ front ends without putting

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them in your <tt>PATH</tt> or typing in their complete pathnames.

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</dl>

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<h3><a name="unpack">Unpacking the LLVM Archives</a></h3>

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If you have the LLVM distribution, you will need to unpack it before you

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can begin to compile it. LLVM is distributed as a set of four files. Each

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file is a TAR archive that is compressed with the gzip program.

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The four files are as follows:

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<dt>llvm.tar.gz

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<dd>This is the source code to the LLVM suite.

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<dt>cfrontend.sparc.tar.gz

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<dd>This is the binary release of the GCC front end for Solaris/Sparc.

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<dt>cfrontend.x86.tar.gz

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<dd>This is the binary release of the GCC front end for Linux/x86.

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<dt>cfrontend-src.tar.gz

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<dd>This is the source code release of the GCC front end.

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</dl>

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<h3><a name="checkout">Checkout LLVM from CVS</a></h3>

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If you have access to our CVS repository, you can get a fresh copy of

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the entire source code. All you need to do is check it out from CVS as

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follows:

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<ul>

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<li><tt>cd where-you-want-llvm-to-live</tt>

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<li><tt>cvs -d CVSROOTDIR checkout llvm</tt>

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</ul>

423

424

This will create an '<tt>llvm</tt>' directory in the current

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directory and fully populate it with the LLVM source code, Makefiles,

426

test directories, and local copies of documentation files.

427

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Note that the GCC front end is not included in the CVS repository. You

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should have either downloaded the source, or better yet, downloaded the

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binary distribution for your platform.

432

433

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<h3><a name="installcf">Install the GCC Front End</a></h3>

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437

438

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Before configuring and compiling the LLVM suite, you need to extract the

440

LLVM GCC front end from the binary distribution. It is used for building the

441

bytecode libraries later used by the GCC front end for linking programs, and

442

its location must be specified when the LLVM suite is configured.

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To install the GCC front end, do the following:

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<ol>

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<li><tt>cd where-you-want-the-front-end-to-live</tt>

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<li><tt>gunzip --stdout cfrontend.platform.tar.gz | tar -xvf

-</tt>

</ol>

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<h3><a name="config">Local LLVM Configuration</a></h3>

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455

456

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Once checked out from the CVS repository, the LLVM suite source code

458

must be configured via the <tt>configure</tt> script. This script sets

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variables in <tt>llvm/Makefile.config</tt> and

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<tt>llvm/include/Config/config.h</tt>. It also populates OBJ_ROOT with

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the Makefiles needed to build LLVM.

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463

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The following environment variables are used by the <tt>configure</tt>

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script to configure the build system:

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<tr>

<th>Variable</th>

<th>

Purpose

</th>

</tr>

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<tr>

<td>

Tells <tt>configure</tt> which C compiler to use. By default,

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<tt>configure</tt> will look for the first GCC compiler in

481

<tt>PATH</tt>. Use this variable to override

482

<tt>configure</tt>'s default behavior.

</td>

</tr>

<tr>

<td>

Tells <tt>configure</tt> which C++ compiler to use. By default,

490

<tt>configure</tt> will look for the first GCC compiler in

491

<tt>PATH</tt>. Use this variable to override

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<tt>configure</tt>'s default behavior.

</td>

</tr>

</table>

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The following options can be used to set or enable LLVM specific options:

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<dt>--with-llvmgccdir=LLVMGCCDIR

503

<dd>

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Path to the location where the LLVM C front end binaries and

505

associated libraries will be installed.

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507

<dt>--enable-optimized

508

<dd>

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Enables optimized compilation by defaulat (debugging symbols are removed

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and GCC optimization flags are enabled). The default is to use an

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unoptimized build (also known as a debug build).

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513

<dt>--enable-jit

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<dd>

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Compile the Just In Time (JIT) functionality. This is not available

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on all platforms. The default is dependent on platform, so it is best

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to explicitly enable it if you want it.

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519

<dt>--enable-spec2000

520

<dt>--enable-spec2000=<<tt>directory</tt>>

521

<dd>

522

Enable the use of SPEC2000 when testing LLVM. This is disabled by default

523

(unless <tt>configure</tt> find SPEC2000 installed). By specifying

524

<tt>directory</tt>, you can tell configure where to find the SPEC2000

525

benchmarks. If <tt>directory</tt> is left unspecified, it

526

<tt>configure</tt> uses a default value for our internal

527

installation of SPEC2000.

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</dl>

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531

To configure LLVM, follow these steps:

532

<ol>

533

<li>Change directory into the object root directory:

<li>Run the <ttconfigure</tt> script located in the LLVM source tree:

539

540

<tt>SRC_ROOT/configure</tt>

</ol>

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In addition to running <tt>configure</tt>, you must set the

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546

<tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.

547

This environment variable is used to locate "system" libraries like

548

"<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set

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to the absolute path for the bytecode-libs subdirectory of the GCC front end

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install, or LLVMGCCDIR/llvm-gcc/bytecode-libs. For example, one might

551

set <tt>LLVM_LIB_SEARCH_PATH</tt> to

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<tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86

553

version of the C front-end on our research machines.

554

555

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<h3><a name="compile">Compiling the LLVM Suite Source Code</a></h3>

557

558

559

Once you have configured LLVM, you can build it. There are three types of

builds:

<dt>Debug Builds

<dd>

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These builds are the default when one types <tt>gmake</tt> (unless the

566

<tt>--enable-optimized</tt> option was used during configuration). They

567

compile the tools and libraries with debugging information.

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569

570

<dt>Release (Optimized) Builds

571

<dd>

572

These builds are enabled with the <tt>--enable-optimized</tt> option to

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<tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the

574

<tt>gmake</tt> command line. They compile the tools and libraries with GCC

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optimizer flags on and strip debugging information from the libraries

576

and executables it generates.

<dt>Profile Builds

<dd>

These builds are for use with profiling. They compile profiling

582

information into the code for use with programs like <tt>gprof</tt>.

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Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>

584

on the <tt>gmake</tt> command line.

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</dl>

586

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Once you have LLVM configured, you can build it by entering the OBJ_ROOT

588

directory and issuing the following command:

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589

John Criswell

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<tt>gmake</tt>

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592

593

If you have multiple processors in your machine, you may wish to use some

594

of the parallel build options provided by GNU Make. For example, you could

use the command:

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<tt>gmake -j2</tt>

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601

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There are several special targets which are useful when working with the LLVM

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source code:

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<dt><tt>gmake clean</tt>

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607

<dd>

608

Removes all files generated by the build. This includes object files,

609

generated C/C++ files, libraries, and executables.

610

611

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<dt><tt>gmake distclean</tt>

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[diff] [blame]

613

<dd>

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[diff] [blame]

614

Removes everything that <tt>gmake clean</tt> does, but also removes

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[diff] [blame]

615

files generated by <tt>configure</tt>. It attempts to return the

616

source tree to the original state in which it was shipped.

617

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619

<dt><tt>gmake install</tt>

620

<dd>

621

Installs LLVM files into the proper location. For the most part,

622

this does nothing, but it does install bytecode libraries into the

623

GCC front end's bytecode library directory. If you need to update

624

your bytecode libraries, this is the target to use once you've built

them.

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628

</dl>

629

630

It is also possible to override default values from <tt>configure</tt> by

631

declaring variables on the command line. The following are some examples:

632

633

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<dt><tt>gmake ENABLE_OPTIMIZED=1</tt>

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[diff] [blame]

635

<dd>

636

Perform a Release (Optimized) build.

637

638

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[diff] [blame]

639

<dt><tt>gmake ENABLE_PROFILING=1</tt>

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[diff] [blame]

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<dd>

641

Perform a Profiling build.

642

643

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[diff] [blame]

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<dt><tt>gmake VERBOSE=1</tt>

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[diff] [blame]

645

<dd>

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646

Print what <tt>gmake</tt> is doing on standard output.

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[diff] [blame]

</dl>

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650

Every directory in the LLVM object tree includes a <tt>Makefile</tt> to

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[diff] [blame]

651

build it and any subdirectories that it contains. Entering any directory

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[diff] [blame^]

652

inside the LLVM object tree and typing <tt>gmake</tt> should rebuild

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[diff] [blame]

653

anything in or below that directory that is out of date.

654

655

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<h3><a name="objfiles">The Location of LLVM Object Files</a></h3>

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[diff] [blame]

657

658

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[diff] [blame]

659

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660

The LLVM build system is capable of sharing a single LLVM source tree among

661

several LLVM builds. Hence, it is possible to build LLVM for several

662

different platforms or configurations using the same source tree.

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[diff] [blame]

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664

This is accomplished in the typical autoconf manner:

665

<ul>

666

<li>Change directory to where the LLVM object files should live:

667

668

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[diff] [blame]

669

John Criswell

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<li>Run the <tt>configure</tt> script found in the LLVM source directory:

671

672

<tt>SRC_ROOT/configure</tt>

673

</ul>

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[diff] [blame]

674

John Criswell

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[diff] [blame]

675

676

The LLVM build will place files underneath OBJ_ROOT in directories

677

named after the build type:

678

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[diff] [blame]

679

John Criswell

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[diff] [blame]

<dt>Debug Builds

<dd>

<dt>Tools

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[diff] [blame^]

685

<dd><tt>OBJ_ROOT/tools/Debug</tt>

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[diff] [blame]

686

<dt>Libraries

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[diff] [blame^]

687

<dd><tt>OBJ_ROOT/lib/Debug</tt>

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[diff] [blame]

688

</dl>

689

John Criswell

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[diff] [blame]

690

John Criswell

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[diff] [blame]

<dt>Release Builds

<dd>

<dt>Tools

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[diff] [blame^]

695

<dd><tt>OBJ_ROOT/tools/Release</tt>

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[diff] [blame]

696

<dt>Libraries

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[diff] [blame^]

697

<dd><tt>OBJ_ROOT/lib/Release</tt>

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[diff] [blame]

698

</dl>

699

Chris Lattner

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[diff] [blame]

700

John Criswell

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[diff] [blame]

<dt>Profile Builds

<dd>

<dt>Tools

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[diff] [blame^]

705

<dd><tt>OBJ_ROOT/tools/Profile</tt>

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[diff] [blame]

706

<dt>Libraries

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[diff] [blame^]

707

<dd><tt>OBJ_ROOT/lib/Profile</tt>

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[diff] [blame]

708

</dl>

709

</dl>

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[diff] [blame]

710

711

712

713

<h2><a name="layout">Program Layout</a></h2>

714

</center>

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[diff] [blame^]

715

<hr>

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[diff] [blame]

716

717

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719

One useful source of information about the LLVM source base is the LLVM <a

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[diff] [blame]

720

href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a

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721

href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.

722

The following is a brief introduction to code layout:

723

John Criswell

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[diff] [blame]

724

725

726

<h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>

727

728

729

Every directory checked out of CVS will contain a <tt>CVS</tt> directory;

730

for the most part these can just be ignored.

731

732

733

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[diff] [blame]

734

<h3><a name="include"><tt>llvm/include</tt></a></h3>

735

736

737

This directory contains public header files exported from the LLVM

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[diff] [blame]

738

library. The three main subdirectories of this directory are:

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[diff] [blame]

739

John Criswell

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[diff] [blame]

740

<ol>

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[diff] [blame]

741

<li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM

742

specific header files. This directory also has subdirectories for

743

different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,

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[diff] [blame^]

744

<tt>Target</tt>, <tt>Transforms</tt>, etc...

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[diff] [blame]

745

746

<li><tt>llvm/include/Support</tt> - This directory contains generic

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[diff] [blame]

747

support libraries that are independent of LLVM, but are used by LLVM.

John Criswell

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[diff] [blame]

748

For example, some C++ STL utilities and a Command Line option processing

749

library.

750

751

<li><tt>llvm/include/Config</tt> - This directory contains header files

752

configured by the <tt>configure</tt> script. They wrap "standard" UNIX

753

and C header files. Source code can include these header files which

754

automatically take care of the conditional #includes that the configure

755

script generates.

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[diff] [blame]

756

</ol>

John Criswell

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[diff] [blame]

757

758

759

760

761

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[diff] [blame]

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This directory contains most of the source files of the LLVM system. In

763

LLVM almost all

764

code exists in libraries, making it very easy to share code among the

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[diff] [blame]

765

different <a href="#tools">tools</a>.

766

767

768

<dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM

769

source files that implement core classes like Instruction and BasicBlock.

770

771

<dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code

772

for the LLVM assembly language parser library.

773

774

<dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading

775

and write LLVM bytecode.

776

777

<dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C

778

converter.

779

780

<dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of

781

different program analyses, such as Dominator Information, Call Graphs,

782

Induction Variables, Interval Identification, Natural Loop Identification,

783

etc...

784

785

<dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source

786

code for the LLVM to LLVM program transformations, such as Aggressive Dead

787

Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop

John Criswell

0c4dccc

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[diff] [blame]

788

Invarient Code Motion, Dead Global Elimination, and many others...

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[diff] [blame]

789

790

<dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that

791

describe various target architectures for code generation. For example,

792

the llvm/lib/Target/Sparc directory holds the Sparc machine

793

description.

794

795

<dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts

796

of the code generator: Instruction Selector, Instruction Scheduling, and

797

Register Allocation.

798

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[diff] [blame]

799

<dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code

800

that corresponds to the header files located in

801

<tt>llvm/include/Support/</tt>.

802

</dl>

803

804

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[diff] [blame^]

805

<h3><a name="runtime"><tt>llvm/runtime</tt></a></h3>

806

807

808

809

This directory contains libraries which are compiled into LLVM bytecode and

810

used when linking programs with the GCC front end. Most of these libraries

811

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.

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[diff] [blame]

821

822

823

824

This directory contains regression tests and source code that is used to

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[diff] [blame^]

825

test the LLVM infrastructure.

826

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

827

828

829

<h3><a name="tools"><tt>llvm/tools</tt></a></h3>

830

831

832

The tools directory contains the executables built out of the

833

libraries above, which form the main part of the user interface. You can

834

always get help for a tool by typing <tt>tool_name --help</tt>. The

835

following is a brief introduction to the most important tools.

836

837

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

838

<dt>

839

840

<dt><tt>analyze</tt><dd> <tt>analyze</tt> is used to run a specific

841

analysis on an input LLVM bytecode file and print out the results. It is

842

primarily useful for debugging analyses, or familiarizing yourself with

843

what an analysis does.

844

845

<dt><tt>bugpoint</tt><dd> <tt>bugpoint</tt> is used to debug

846

optimization passes or code generation backends by narrowing down the

847

given test case to the minimum number of passes and/or instructions that

848

still cause a problem, whether it is a crash or miscompilation. See <a

849

href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information

850

on using <tt>bugpoint</tt>.

851

852

<dt><tt>llvm-ar</tt><dd>The archiver produces an archive containing

853

the given LLVM bytecode files, optionally with an index for faster

854

lookup.

855

Misha Brukman

2003-08-28 22:02:50 +0000

[diff] [blame]

856

<dt><tt>llvm-as</tt><dd>The assembler transforms the human readable

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

857

LLVM assembly to LLVM bytecode.

858

Misha Brukman

2003-08-28 22:02:50 +0000

[diff] [blame]

859

<dt><tt>llvm-dis</tt><dd>The disassembler transforms the LLVM

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

860

bytecode to human readable LLVM assembly. Additionally, it can convert

Misha Brukman

2003-08-28 22:02:50 +0000

[diff] [blame]

861

LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

862

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

863

<dt><tt>llvm-link</tt><dd> <tt>llvm-link</tt>, not surprisingly,

864

links multiple LLVM modules into a single program.

865

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

866

<dt><tt>lli</tt><dd> <tt>lli</tt> is the LLVM interpreter, which

867

can directly execute LLVM bytecode (although very slowly...). In addition

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

868

to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by

869

specifying <tt>-trace</tt> on the command line). Finally, for

870

architectures that support it (currently only x86 and Sparc), by default,

871

<tt>lli</tt> will function as a Just-In-Time compiler (if the

872

functionality was compiled in), and will execute the code much

873

faster than the interpreter.

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

874

875

<dt><tt>llc</tt><dd> <tt>llc</tt> is the LLVM backend compiler,

Misha Brukman

c56e582

2003-07-03 16:29:36 +0000

[diff] [blame]

876

which translates LLVM bytecode to a SPARC or x86 assembly file.

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

877

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

878

<dt><tt>llvmgcc</tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

879

that has been retargeted to emit LLVM code as the machine code output. It

880

works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,

881

-o</tt> options that are typically used. The source code for the

882

<tt>llvmgcc</tt> tool is currently not included in the LLVM cvs tree

883

because it is quite large and not very interesting.

884

885

<ol>

886

<dt><tt>gccas</tt><dd> This tool is invoked by the

887

<tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This

888

tool actually assembles LLVM assembly to LLVM bytecode,

Misha Brukman

2003-10-06 19:23:34 +0000

[diff] [blame]

889

performs a variety of optimizations, and outputs LLVM bytecode. Thus

890

when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing

891

<tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is

892

an LLVM bytecode file that can be disassembled or manipulated just like

893

any other bytecode file). The command line interface to <tt>gccas</tt>

894

is designed to be as close as possible to the system

895

`<tt>as</tt>' utility so that the gcc frontend itself did not have to be

896

modified to interface to a "weird" assembler.

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

897

898

<dt><tt>gccld</tt><dd> <tt>gccld</tt> links together several LLVM

899

bytecode files into one bytecode file and does some optimization. It is

900

the linker invoked by the gcc frontend when multiple .o files need to be

901

linked together. Like <tt>gccas</tt> the command line interface of

902

<tt>gccld</tt> is designed to match the system linker, to aid

903

interfacing with the GCC frontend.

904

</ol>

905

906

<dt><tt>opt</tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a

907

series of LLVM to LLVM transformations (which are specified on the command

908

line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'

909

command is a good way to get a list of the program transformations

910

available in LLVM.

911

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

912

</dl>

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

913

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

914

915

<h3><a name="utils"><tt>llvm/utils</tt></a></h3>

916

917

918

This directory contains utilities for working with LLVM sourcecode, and some

919

of the utilities are actually required as part of the build process because

920

they are code generators for parts of LLVM infrastructure.

921

922

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

923

<td><tt>Burg/</tt><dd> <tt>Burg</tt> is an instruction selector

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

924

generator -- it builds trees on which it then performs pattern-matching to

925

select instructions according to the patterns the user has specified. Burg

926

is currently used in the Sparc V9 backend.

927

928

<dt><tt>codegen-diff</tt><dd> <tt>codegen-diff</tt> is a script

929

that finds differences between code that LLC generates and code that LLI

930

generates. This is a useful tool if you are debugging one of them,

931

assuming that the other generates correct output. For the full user

932

manual, run <tt>`perldoc codegen-diff'</tt>.

933

934

<dt><tt>cvsupdate</tt><dd> <tt>cvsupdate</tt> is a script that will

935

update your CVS tree, but produce a much cleaner and more organized output

936

than simply running <tt>`cvs up -dP'</tt> will. For example, it will group

937

together all the new and updated files and modified files in separate

938

sections, so you can see at a glance what has changed. If you are at the

939

top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the

940

preferred way of updating the tree.

941

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

942

<dt><tt>emacs/</tt><dd> The <tt>emacs</tt> directory contains

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

943

syntax-highlighting files which will work with Emacs and XEmacs editors,

944

providing syntax highlighting support for LLVM assembly files and TableGen

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

945

description files. For information on how to use the syntax files, consult

946

the <tt>README</tt> file in that directory.

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

947

948

<dt><tt>getsrcs.sh</tt><dd> The <tt>getsrcs.sh</tt> script finds

949

and outputs all non-generated source files, which is useful if one wishes

950

to do a lot of development across directories and does not want to

951

individually find each file. One way to use it is to run, for example:

952

<tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source

953

tree.

954

955

<dt><tt>makellvm</tt><dd> The <tt>makellvm</tt> script compiles all

956

files in the current directory and then compiles and links the tool that

957

is the first argument. For example, assuming you are in the directory

958

<tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,

959

simply running <tt>makellvm llc</tt> will make a build of the current

960

directory, switch to directory <tt>llvm/tools/llc</tt> and build it,

961

causing a re-linking of LLC.

962

963

<dt><tt>NightlyTest.pl</tt> and

964

<tt>NightlyTestTemplate.html</tt><dd> These files are used in a

965

cron script to generate nightly status reports of the functionality of

966

tools, and the results can be seen by following the appropriate link on

967

the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.

968

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

969

<dt><tt>TableGen/</tt><dd> The <tt>TableGen</tt> directory contains

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

970

the tool used to generate register descriptions, instruction set

Chris Lattner

a8f5de3

2003-08-11 18:53:14 +0000

[diff] [blame]

971

descriptions, and even assemblers from common TableGen description

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

972

files.

973

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

974

<dt><tt>vim/</tt><dd> The <tt>vim</tt> directory contains

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

975

syntax-highlighting files which will work with the VIM editor, providing

976

syntax highlighting support for LLVM assembly files and TableGen

Misha Brukman

2003-08-11 19:13:12 +0000

[diff] [blame]

977

description files. For information on how to use the syntax files, consult

978

the <tt>README</tt> file in that directory.

Misha Brukman

2003-08-11 18:45:46 +0000

[diff] [blame]

</dl>

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

982

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

983

<h2><center><a name="cfront">Compiling the LLVM GCC Front End</center></h2>

984

<hr>

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

985

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

989

This step is optional if you have the GCC front end binary distribution for

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

your platform.

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

994

Now that you have the LLVM suite built, you can build the GCC front end. For

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

995

those of you that have built GCC before, the process is very similar.

996

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

997

Be forewarned, though: the build system for the GCC front end is not as

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

998

polished as the rest of the LLVM code, so there will be many warnings and

999

errors that you will need to ignore for now:

1000

1001

<ol>

1002

<li>Ensure that <tt>OBJ_ROOT/llvm/tools/Debug</tt> is at the

1003

end of your <tt>PATH</tt> environment variable. The front end

1004

build needs to know where to find the LLVM tools, but you want to

1005

ensure that these tools are not found before the system assembler and

1006

linker that you normally use for compilation.

1007

1008

<li><tt>cd GCCOBJ</tt>

1009

1010

<li>Configure the source code:

1011

<ul>

1012

<li>On Linux/x86, use

1013

<ul>

1014

<li><tt>GCCSRC/configure --prefix=LLVMGCCDIR

1015

--enable-languages=c</tt>

1016

</ul>

1017

1018

<li>On Solaris/Sparc, use

1019

<ul>

1020

<li><tt>GCCSRC/configure --prefix=LLVMGCCDIR

1021

--enable-languages=c --target=sparcv9-sun-solaris2</tt>

</ul>

</ul>

<li><tt>gmake</tt>

<li>The build will eventually fail. Don't worry; chances are good that

1028

everything that needed to build is built.

1029

1030

<li><tt>gmake -k install</tt>

</ol>

Once this is done, you should have a built front end compiler in

<tt>LLVMGCCDIR</tt>.

1039

<h2>

1040

<center><a name="tutorial">An Example Using the LLVM Tool Chain</center>

1041

</h2>

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

1042

<hr>

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

1043

1044

1045

<ol>

1046

<li>First, create a simple C file, name it 'hello.c':

<pre>

#include <stdio.h>

int main() {

printf("hello world\n");

return 0;

}

</pre>

<li>Next, compile the C file into a LLVM bytecode file:

1056

1057

<tt>% llvmgcc hello.c -o hello</tt>

1058

1059

This will create two result files: <tt>hello</tt> and

1060

<tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that

1061

corresponds the the compiled program and the library facilities that it

1062

required. <tt>hello</tt> is a simple shell script that runs the bytecode

1063

file with <tt>lli</tt>, making the result directly executable.

1064

1065

<li>Run the program. To make sure the program ran, execute one of the

1066

following commands:

John Criswell

8df90e0

2003-06-11 20:46:40 +0000

[diff] [blame]

1067

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

<tt>% ./hello</tt>

or

<tt>% lli hello.bc</tt>

1073

Misha Brukman

2003-08-28 22:02:50 +0000

[diff] [blame]

1074

<li>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

1075

code:

1076

Misha Brukman

2003-08-28 22:02:50 +0000

[diff] [blame]

1077

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

1078

1079

<li>Compile the program to native Sparc assembly using the code

Misha Brukman

c56e582

2003-07-03 16:29:36 +0000

[diff] [blame]

1080

generator (assuming you are currently on a Sparc system):

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

1081

1082

<tt>% llc hello.bc -o hello.s</tt>

1083

1084

<li>Assemble the native sparc assemble file into a program:

1085

1086

<tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt>

1087

1088

<li>Execute the native sparc program:

1089

1090

<tt>% ./hello.sparc</tt>

</ol>

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

1096

<h2>

1097

<center><a name="problems">Common Problems</a></center>

1098

</h2>

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

1099

<hr>

John Criswell

2003-07-03 16:01:38 +0000

[diff] [blame]

1100

1101

1102

Below are common problems and their remedies:

1103

1104

1105

<dt>When I run configure, it finds the wrong C compiler.

1106

<dd>

1107

The <tt>configure</tt> script attempts to locate first <tt>gcc</tt> and

1108

then <tt>cc</tt>, unless it finds compiler paths set in <tt>CC</tt> and

1109

<tt>CXX</tt> for the C and C++ compiler, respectively.

1110

1111

If <tt>configure</tt> finds the wrong compiler, either adjust your

1112

<tt>PATH</tt> environment variable or set <tt>CC</tt> and <tt>CXX</tt>

explicitly.

<dt>I compile the code, and I get some error about /localhome.

1117

<dd>

1118

There are several possible causes for this. The first is that you

1119

didn't set a pathname properly when using <tt>configure</tt>, and it

1120

defaulted to a pathname that we use on our research machines.

1121

1122

Another possibility is that we hardcoded a path in our Makefiles. If

1123

you see this, please email the LLVM bug mailing list with the name of

1124

the offending Makefile and a description of what is wrong with it.

1125

1126

<dt>The <tt>configure</tt> script finds the right C compiler, but it

1127

uses the LLVM linker from a previous build. What do I do?

1128

<dd>

1129

The <tt>configure</tt> script uses the <tt>PATH</tt> to find

1130

executables, so if it's grabbing the wrong linker/assembler/etc, there

1131

are two ways to fix it:

1132

<ol>

1133

<li>Adjust your <tt>PATH</tt> environment variable so that the

1134

correct program appears first in the <tt>PATH</tt>. This may work,

1135

but may not be convenient when you want them first in your

path for other work.

<li>Run <tt>configure</tt> with an alternative <tt>PATH</tt> that

1140

is correct. In a Borne compatible shell, the syntax would be:

1141

1142

<tt>PATH=<the path without the bad program> ./configure ...</tt>

1143

1144

This is still somewhat inconvenient, but it allows

1145

<tt>configure</tt> to do its work without having to adjust your

1146

<tt>PATH</tt> permanently.

1147

</ol>

John Criswell

3c852b6

2003-08-08 22:43:39 +0000

[diff] [blame]

1148

1149

<dt>I've upgraded to a new version of LLVM, and I get strange build

1150

errors.

1151

<dd>

1152

Sometimes changes to the LLVM source code alters how the build system

1153

works. Changes in libtool, autoconf, or header file dependencies are

1154

especially prone to this sort of problem.

1155

1156

The best thing to try is to remove the old files and re-build. In most

1157

cases, this takes care of the problem. To do this, just type <tt>make

1158

clean</tt> and then <tt>make</tt> in the directory that fails to build.

1159

1160

John Criswell

2003-07-03 16:01:38 +0000

[diff] [blame]

1161

</dl>

1162

1163

John Criswell

2003-07-08 20:35:59 +0000

[diff] [blame]

1164

<h2><center><a name="links">Links</a></center></h2>

John Criswell

2003-10-10 14:26:14 +0000

[diff] [blame^]

1165

<hr>

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

1166

1167

1168

This document is just an introduction to how to use LLVM to do

1169

some simple things... there are many more interesting and complicated things

1170

that you can do that aren't documented here (but we'll gladly accept a patch

1171

if you want to write something up!). For more information about LLVM, check

out:

<ul>

<li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>

1176

<li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>

John Criswell

2003-07-03 16:01:38 +0000

[diff] [blame]

1177

<li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project that Uses LLVM</a></li>

John Criswell

2003-06-12 19:34:44 +0000

[diff] [blame]

</ul>

<hr>

If you have any questions or run into any snags (or you have any

1183

additions...), please send an email to

1184

<a href="mailto:sabre@nondot.org">Chris Lattner</a>.

1185

1186

1187

Chris Lattner

a8f5de3

2003-08-11 18:53:14 +0000

[diff] [blame]

1188

Last modified: Mon Aug 11 13:52:22 CDT 2003

John Criswell