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

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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="#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="#checkout">Checkout LLVM from CVS</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="#build">Building the LLVM C Front End</a>

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<li><a href="#objfiles">The location for 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">CVS 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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</ol>

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<li><a href="#tutorial">An example using the LLVM tool chain</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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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 code into LLVM bytecode. Currently, the C front end

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is a modified version of GCC 3.4 (we track the GCC 3.4 development).

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Once compiled into LLVM bytecode, a program can be manipulated with the

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LLVM tools.

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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:

<ul>

<li> Linux on x86

<ul>

<li> Approximately 700 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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</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 1.03 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

</ul>

</ul>

</ul>

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

<dd>

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>

The <a href="starting">next section</a> of this guide is meant to get

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you up and running with LLVM and to give you some basic information about

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the LLVM environment. The <a href"#quickstart">first subsection</a> gives

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a short summary for those who are already familiar with the system and

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want to get started as quickly as possible.

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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="starting">Getting Started</a></h2>

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</center>

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<h3><a name="quickstart">Getting Started Quickly (A Summary)</a></h3>

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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>Build the LLVM suite

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<ol>

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

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<li>Run <tt>configure</tt> to configure the Makefiles and header files.

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Useful options include:

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<ul>

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

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Specify where object files should be placed during the build.

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

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Specify where the LLVM C frontend is going to be installed.

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</ul>

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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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<li>Build the LLVM C Front End (optional)

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<ol>

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<li>Create a directory for the object files to live.

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<li><tt>cd object file directory</tt>

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<li>Run <tt>Pathname-to-where-the-source-code-lives/configure --prefix=LLVMGCCDIR</tt> to configure GCC.

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<li><tt>make bootstrap</tt>

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<li><tt>make install</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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other sub-sections below 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.

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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.

<dt>OBJ_ROOT

<dd>

This is the top level directory for where the LLVM suite object files

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will be placed during the build.

<dt>LLVMGCCDIR

<dd>

This is the pathname to the location where the LLVM C Front End will

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be installed. Note that the C front end does not need to be installed

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during the LLVM suite build; you will just need to know where it will

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go for configuring the build system and running the test suite later.

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

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

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<dt>GCCSRC

<dd>

This is the pathname of the directory where the LLVM C front end source

code can be found.

<dt>GCCOBJ

<dd>

This is the pathname of the directory where the LLVM C front end object

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code will be placed during the build. It can be safely removed once

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the build is complete.

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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 C front end find bytecode

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libraries that it will need for compilation.

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<dt><tt>PATH</tt>=<tt>${PATH}:OBJ_ROOT/llvm/tools/Debug</tt>

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<dd>

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Adding this directory to the end of your path will allow the

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compilation of the C front end to find the LLVM tools. The LLVM tools

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are needed for the C front end compile.

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<dt><tt>CC</tt>=Pathname to your GCC compiler

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<dd>

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The GCC compiler that you want to use must be the first C compiler in

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your <tt>PATH</tt>. Otherwise, set this variable so that

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<tt>configure</tt> will use the GCC compiler that you want to use.

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<dt><tt>CXX</tt>=Pathname to your GCC C++ compiler

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<dd>

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The GCC compiler that you want to use must be the first C++ compiler in

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your <tt>PATH</tt>. Otherwise, set this variable so that

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<tt>configure</tt> will use the GCC compiler that you want to use.

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<dt><tt>CVSROOT</tt>=CVSROOT

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<dd>

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This environment variable tells CVS where to find the CVS repository.

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

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<dd>

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This alias allows you to use the LLVM C front end without putting it in

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your <tt>PATH</tt> or typing in its complete pathname.

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</dl>

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

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To get a fresh copy of the entire source code, all you

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need to do is check it out from CVS as 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>

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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,

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test directories, and local copies of documentation files.

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Note that the C 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.

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

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

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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>.

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

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configure Makefile.config:

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<ul>

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<li>CXX = Pathname of the C++ compiler to use.

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<li>CC = Pathname of the C compiler to use.

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</ul>

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

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<dt>--with-objroot=OBJ_ROOT

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<dd>

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Path to the directory where

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object files, libraries, and executables should be placed.

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If this is set to <tt>.</tt>, then the object files will be placed

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within the source code tree. If left unspecified, the default value is

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<tt>.</tt>.

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(See the Section on <a href=#objfiles>

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The location for LLVM object files</a>

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for more information.)

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<dt>--with-llvmgccdir=LLVMGCCDIR

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<dd>

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

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associated libraries will be installed.

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<dt>--enable-optimized

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<dd>

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Enables optimized compilation (debugging symbols are removed and GCC

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

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build (also known as a debug build).

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<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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</dl>

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

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

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

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"<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 C front-end

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

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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

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

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

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

builds:

<dt>Debug Builds

<dd>

These builds are the default. They compile the tools and libraries

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with debugging information.

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<dt>Release (Optimized) Builds

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<dd>

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

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<tt>configure</tt>. They compile the tools and libraries with GCC

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optimizer flags on and strip debugging information from the libraries

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and executables it generates.

<dt>Profile Builds

<dd>

These builds are for use with profiling. They compile profiling

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

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Profile builds must be started by setting variables on the

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<tt>make</tt> command line.

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</dl>

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

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<tt>llvm</tt> directory and issuing the following command:

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

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

use the command:

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

source code:

<dt><tt>make clean</tt>

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<dd>

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

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

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<dt><tt>make distclean</tt>

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<dd>

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

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

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

</dl>

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

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

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

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<dd>

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Perform a Release (Optimized) build.

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

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<dd>

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Perform a Profiling build.

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

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<dd>

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

</dl>

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

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

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inside the LLVM source tree and typing <tt>make</tt> should rebuild

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

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<h3><a name="build">Building the LLVM C Front End</a></h3>

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This step is optional if you have the C front end binary distrubtion for

your platform.

Now that you have the LLVM Suite built, you can build the C front end. For

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

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

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

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errors that you will need to ignore for now:

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<ol>

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

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

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

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<li>Configure the source code:

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<ul>

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<li>On Linux/x86, use

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<ul>

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

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--enable-languages=c</tt>

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</ul>

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<li>On Solaris/Sparc, use

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<ul>

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

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

</ul>

</ul>

<li><tt>make bootstrap</tt>

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

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everything that needed to build is built.

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<li><tt>make install</tt>

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</ol>

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At this point, you should have a working copy of the LLVM C front end

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installed in LLVMGCCDIR.

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<h3><a name="objfiles">The location for LLVM object files</a></h3>

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The LLVM build system sends most output files generated during the build

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into the directory defined by the variable OBJ_ROOT in

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<tt>llvm/Makefile.config</tt>, which is set by the --with-objroot

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option in <tt>configure</tt>. This can be either just your normal LLVM

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source tree or some other directory writable by you. You may wish to put

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object files on a different filesystem either to keep them from being backed

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up or to speed up local builds.

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If OBJ_ROOT is specified, then the build system will create a

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directory tree underneath it that resembles the source code's pathname

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relative to your home directory.

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For example, suppose that OBJ_ROOT is set to <tt>/tmp</tt> and the

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LLVM suite source code is located in <tt>/usr/home/joe/src/llvm</tt>, where

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<tt>/usr/home/joe</tt> is the home directory of a user named Joe. Then,

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the object files will be placed in <tt>/tmp/src/llvm</tt>.

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The LLVM build will place files underneath OBJ_ROOT in directories

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named after the build type:

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<dt>Debug Builds

<dd>

<dt>Tools

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

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<dt>Libraries

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

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</dl>

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<dt>Release Builds

<dd>

<dt>Tools

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

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<dt>Libraries

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

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</dl>

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<dt>Profile Builds

<dd>

<dt>Tools

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

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<dt>Libraries

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

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</dl>

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</dl>

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611

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

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</center>

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

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

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

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following is a brief introduction to code layout:

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

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

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for the most part these can just be ignored.

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

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This directory contains public header files exported from the LLVM

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library. The three main subdirectories of this directory are:

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<ol>

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

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specific header files. This directory also has subdirectories for

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

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

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

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

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

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library.

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

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

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

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automatically take care of the conditional #includes that the configure

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script generates.

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</ol>

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

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LLVM almost all

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

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

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

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source files that implement core classes like Instruction and BasicBlock.

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

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for the LLVM assembly language parser library.

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

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and write LLVM bytecode.

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

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converter.

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

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

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Induction Variables, Interval Identification, Natural Loop Identification,

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etc...

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

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

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Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop

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Invarient Code Motion, Dead Global Elimination, Pool Allocation, and many

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others...

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

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describe various target architectures for code generation. For example,

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

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description.

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

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

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Register Allocation.

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<dt><tt>llvm/lib/Reoptimizer/</tt><dd> This directory holds code related

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to the runtime reoptimizer framework that is currently under development.

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

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that corresponds to the header files located in

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

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</dl>

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

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test the LLVM infrastructure...

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

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The tools directory contains the executables built out of the

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

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

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following is a brief introduction to the most important tools.

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

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LLVM assembly to LLVM bytecode.

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

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to human readable LLVM assembly. Additionally it can convert LLVM

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

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

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

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to a simple interpreter, <tt>lli</tt> is also has debugger and tracing

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modes (entered by specifying <tt>-debug</tt> or <tt>-trace</tt> on the

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command line, respectively). Finally, for architectures that support it

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(currently only x86 and Sparc), by default, <tt>lli</tt> will function as

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a Just-In-Time compiler (if the functionality was compiled in), and will

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execute the code much faster than the interpreter.

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

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

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

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

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

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

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

747

because it is quite large and not very interesting.

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<ol>

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

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

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tool actually assembles LLVM assembly to LLVM bytecode,

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performs a variety of optimizations,

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and outputs LLVM bytecode. Thus when you invoke <tt>llvmgcc -c x.c -o

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x.o</tt>, you are causing <tt>gccas</tt> to be run, which writes the

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<tt>x.o</tt> file (which is an LLVM bytecode file that can be

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disassembled or manipulated just like any other bytecode file). The

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command line interface to <tt>gccas</tt> is designed to be as close as

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possible to the system '<tt>as</tt>' utility so that the gcc

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frontend itself did not have to be modified to interface to a "weird"

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assembler.

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

764

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

765

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

766

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

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

768

interfacing with the GCC frontend.

769

</ol>

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

772

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

773

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

774

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

available in LLVM.

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

779

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

780

primarily useful for debugging analyses, or familiarizing yourself with

781

what an analysis does.

</dl>

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<h2><a name="tutorial">An example using the LLVM tool chain</h2>

787

788

789

<ol>

790

<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:

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801

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

802

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

804

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

805

corresponds the the compiled program and the library facilities that it

806

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

807

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

808

809

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

810

following commands:

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<tt>% ./hello</tt>

or

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

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818

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

code:

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

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

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

827

828

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

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

831

832

<li>Execute the native sparc program:

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

</ol>

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<h2><a name="help">Common Problems</a></h2>

841

842

843

Below are common problems and their remedies:

844

845

846

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

847

<dd>

848

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

849

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

850

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

851

852

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

853

<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.

858

<dd>

859

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

860

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

861

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

862

863

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

864

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

865

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

866

867

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

868

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

869

<dd>

870

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

871

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

872

are two ways to fix it:

873

<ol>

874

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

875

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

876

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

881

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

882

883

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

884

885

This is still somewhat inconvenient, but it allows

886

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

887

<tt>PATH</tt> permanently.

</ol>

</dl>

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

893

894

895

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

896

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

897

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

898

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>

903

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

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

John Criswell