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| <title>Getting Started with LLVM System</title> |
| </head> |
| |
| <body bgcolor=white> |
| <center><h1>Getting Started with the LLVM System<br><font size=3>By: <a |
| href="mailto:gshi1@uiuc.edu">Guochun Shi</a>, |
| <a href="mailto:sabre@nondot.org">Chris Lattner</a>, |
| <a href="mailto:criswell@uiuc.edu">John Criswell</a>, and |
| <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a> |
| </font></h1></center> |
| |
| <!--=====================================================================--> |
| <h2><a name="Contents">Contents</a></h2> |
| <!--=====================================================================--> |
| |
| <ul> |
| <li><a href="#overview">Overview</a> |
| <ol> |
| <li><a href="#requirements">Requirements</a> |
| <ol> |
| <li><a href="#hardware">Hardware</a> |
| <li><a href="#software">Software</a> |
| </ol> |
| </ol> |
| <li><a href="#starting">Getting started with LLVM</a> |
| <ol> |
| <li><a href="#quickstart">Getting started quickly (a summary)</a> |
| <li><a href="#terminology">Terminology and Notation</tt></a> |
| <li><a href="#environment">Setting up your environment</a> |
| <li><a href="#unpack">Unpacking the LLVM Archives</a> |
| <li><a href="#checkout">Checkout LLVM from CVS</a> |
| <li><a href="#config">Local LLVM Configuration</tt></a> |
| <li><a href="#compile">Compiling the LLVM Suite Source Code</a> |
| <li><a href="#build">Compiling the LLVM C Front End</a> |
| <li><a href="#objfiles">The location for object files</tt></a> |
| </ol> |
| <li><a href="#layout">Program layout</a> |
| <ol> |
| <li><a href="#cvsdir">CVS directories</a> |
| <li><a href="#include"><tt>llvm/include</tt></a> |
| <li><a href="#lib"><tt>llvm/lib</tt></a> |
| <li><a href="#test"><tt>llvm/test</tt></a> |
| <li><a href="#tools"><tt>llvm/tools</tt></a> |
| </ol> |
| <li><a href="#tutorial">An example using the LLVM tool chain</a> |
| <li><a href="#links">Links</a> |
| </ul> |
| |
| |
| <!--=====================================================================--> |
| <center> |
| <h2><a name="overview"><b>Overview</b></a></h2> |
| </center> |
| <!--=====================================================================--> |
| |
| Welcome to LLVM! In order to get started, you first need to know some |
| basic information. |
| |
| <p> |
| First, LLVM comes in two pieces. The first piece is the LLVM suite. This |
| contains all of the tools, libraries, and header files needed to use the |
| low level virtual machine. It also contains a test suite that can be used |
| to test the LLVM tools and the GCC front end. |
| <p> |
| The second piece is the GCC front end. This component provides a version |
| of GCC that compiles C code into LLVM bytecode. Currently, the C front end |
| is a modified version of GCC 3.4 (we track the GCC 3.4 development). |
| Once compiled into LLVM bytecode, a program can be manipulated with the |
| LLVM tools. |
| |
| <!--=====================================================================--> |
| <h3><a name="requirements"><b>Requirements</b></a></h3> |
| <!--=====================================================================--> |
| |
| Before you begin to use the LLVM system, review the requirements given |
| below. This may save you some trouble by knowing ahead of time what |
| hardware and software you will need. |
| |
| <!--=====================================================================--> |
| <h4><a name="hardware"><b>Hardware</b></a></h4> |
| <!--=====================================================================--> |
| LLVM is known to work on the following platforms: |
| <ul> |
| <li> Linux on x86 |
| <ul> |
| <li> Approximately 700 MB of Free Disk Space |
| <ul> |
| <li>Source code: 30 MB |
| <li>Object code: 670 MB |
| </ul> |
| </ul> |
| <li> Solaris on SparcV9 (Ultrasparc) |
| <ul> |
| <li> Approximately 1.03 GB of Free Disk Space |
| <ul> |
| <li>Source code: 30 MB |
| <li>Object code: 1000 MB |
| </ul> |
| </ul> |
| </ul> |
| |
| LLVM <i>may</i> compile on other platforms. The LLVM utilities should work |
| on other platforms, so it should be possible to generate and produce LLVM |
| bytecode on unsupported platforms (although bytecode generated on one |
| platform may not work on another platform). However, the code generators |
| and Just-In-Time (JIT) compilers only generate SparcV9 or x86 machine code. |
| |
| <!--=====================================================================--> |
| <h4><a name="software"><b>Software</b></a></h4> |
| <!--=====================================================================--> |
| <p> |
| |
| Unpacking the distribution requires the following tools: |
| <dl compact> |
| <dt>GNU Zip (gzip) |
| <dt>GNU Tar |
| <dd> |
| These tools are needed to uncompress and unarchive the software. |
| Regular Solaris <tt>tar</tt> may work for unpacking the TAR archive but |
| is untested. |
| </dl> |
| |
| Compiling LLVM requires that you have several different software packages |
| installed: |
| |
| <dl compact> |
| <dt> GCC |
| <dd> |
| The GNU Compiler Collection must be installed with C and C++ language |
| support. GCC 3.2.x works, and GCC 3.x is generally supported. |
| |
| <p> |
| Note that we currently do not support any other C++ compiler. |
| </p> |
| |
| <dt> GNU Make |
| <dd> |
| The LLVM build system relies upon GNU Make extensions. Therefore, you |
| will need GNU Make (sometimes known as gmake) to build LLVM. |
| <p> |
| |
| <dt> Flex and Bison |
| <dd> |
| The LLVM source code is built using flex and bison. You will not be |
| able to configure and compile LLVM without them. |
| <p> |
| |
| <dt> GNU M4 |
| <dd> |
| If you are installing Bison on your machine for the first time, you |
| will need GNU M4 (version 1.4 or higher). |
| </dl> |
| |
| <p> |
| There are some additional tools that you may want to have when working with |
| LLVM: |
| </p> |
| |
| <ul> |
| <li>GNU Autoconf |
| <li>GNU M4 |
| <p> |
| If you want to make changes to the configure scripts, you will need |
| GNU autoconf (2.53 or higher), and consequently, GNU M4 (version 1.4 |
| or higher). |
| </p> |
| </ul> |
| |
| |
| <p>The <a href="starting">next section</a> of this guide is meant to get |
| you up and running with LLVM and to give you some basic information about |
| the LLVM environment. The <a href"#quickstart">first subsection</a> gives |
| a short summary for those who are already familiar with the system and |
| want to get started as quickly as possible. |
| |
| <p>The later sections of this guide describe the <a |
| href="#layout">general layout</a> of the the LLVM source-tree, a <a |
| href="#tutorial">simple example</a> using the LLVM tool chain, and <a |
| href="#links">links</a> to find more information about LLVM or to get |
| help via e-mail. |
| |
| <!--=====================================================================--> |
| <center> |
| <h2><a name="starting"><b>Getting Started</b></a></h2> |
| </center> |
| <!--=====================================================================--> |
| |
| <!--=====================================================================--> |
| <h3><a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a></h3> |
| <!--=====================================================================--> |
| |
| Here's the short story for getting up and running quickly with LLVM: |
| <ol> |
| <li>Build the LLVM suite |
| <ol> |
| <li>Find the path to the CVS repository containing LLVM (we'll call this <i>CVSROOTDIR</i>). |
| <li><tt>cd <i>where-you-want-llvm-to-live</i></tt> |
| <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt> |
| <li><tt>cd llvm</tt> |
| <li>Run <tt>configure</tt> to configure the Makefiles and header files. |
| Useful options include: |
| <ul> |
| <li><tt>--with-objroot=<i>directory</i></tt> |
| <br> |
| Specify where object files should be placed during the build. |
| |
| <li><tt>--with-llvmgccdir=<i>directory</i></tt> |
| <br> |
| Specify where the LLVM C frontend is going to be installed. |
| </ul> |
| <li>Set your LLVM_LIB_SEARCH_PATH environment variable. |
| <li><tt>gmake -k |& tee gnumake.out |
| # this is csh or tcsh syntax</tt> |
| </ol> |
| <p> |
| <li>Build the LLVM C Front End <b>(optional)</b> |
| <ol> |
| <li>Create a directory for the object files to live. |
| <li><tt>cd <i>object file directory</i></tt> |
| <li>Run <tt><i>Pathname-to-where-the-source-code-lives</i>/configure --prefix=<i>LLVMGCCDIR</i></tt> to configure GCC. |
| <li><tt>make bootstrap</tt> |
| <li><tt>make install</tt> |
| </ol> |
| </ol> |
| |
| <p>See <a href="#environment">Setting up your environment</a> on tips to |
| simplify working with the LLVM front-end and compiled tools. See the |
| other sub-sections below for other useful details in working with LLVM, |
| or go straight to <a href="#layout">Program Layout</a> to learn about the |
| layout of the source code tree. |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="terminology">Terminology and Notation</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>Throughout this manual, the following names are used to denote paths |
| specific to the local system and working environment. <i>These are not |
| environment variables you need to set but just strings used in the rest |
| of this document below</i>. In any of the examples below, simply replace |
| each of these names with the appropriate pathname on your local system. |
| All these paths are absolute:</p> |
| <dl compact> |
| <dt>CVSROOTDIR |
| <dd> |
| This is the path for the CVS repository containing the LLVM source |
| code. Ask the person responsible for your local LLVM installation to |
| give you this path. |
| <p> |
| |
| <dt>OBJ_ROOT |
| <dd> |
| This is the top level directory for where the LLVM suite object files |
| will be placed during the build. |
| <p> |
| |
| <dt>LLVMGCCDIR |
| <dd> |
| This is the pathname to the location where the LLVM C Front End will |
| be installed. Note that the C front end does not need to be installed |
| during the LLVM suite build; you will just need to know where it will |
| go for configuring the build system and running the test suite later. |
| <p> |
| For the pre-built C front end binaries, the LLVMGCCDIR is |
| <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>. |
| |
| <dt>GCCSRC |
| <dd> |
| This is the pathname of the directory where the LLVM C front end source |
| code can be found. |
| <p> |
| |
| <dt>GCCOBJ |
| <dd> |
| This is the pathname of the directory where the LLVM C front end object |
| code will be placed during the build. It can be safely removed once |
| the build is complete. |
| </dl> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="environment">Setting up your environment</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p> |
| In order to compile and use LLVM, you will need to set some environment |
| variables. There are also some shell aliases which you may find useful. |
| You can set these on the command line, or better yet, set them in your |
| <tt>.cshrc</tt> or <tt>.profile</tt>. |
| |
| <dl compact> |
| <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/llvm-gcc/bytecode-libs</tt> |
| <dd> |
| This environment variable helps the LLVM C front end find bytecode |
| libraries that it will need for compilation. |
| <p> |
| |
| <dt><tt>PATH</tt>=<tt>${PATH}:<i>OBJ_ROOT</i>/llvm/tools/Debug</tt> |
| <dd> |
| Adding this directory to the end of your path will allow the |
| compilation of the C front end to find the LLVM tools. The LLVM tools |
| are needed for the C front end compile. |
| <p> |
| |
| <dt><tt>CC</tt>=<i>Pathname to your GCC compiler</i> |
| <dd> |
| The GCC compiler that you want to use must be the first C compiler in |
| your <tt>PATH</tt>. Otherwise, set this variable so that |
| <tt>configure</tt> will use the GCC compiler that you want to use. |
| <p> |
| |
| <dt><tt>CXX</tt>=<i>Pathname to your GCC C++ compiler</i> |
| <dd> |
| The GCC compiler that you want to use must be the first C++ compiler in |
| your <tt>PATH</tt>. Otherwise, set this variable so that |
| <tt>configure</tt> will use the GCC compiler that you want to use. |
| <p> |
| |
| <dt><tt>CVSROOT</tt>=<i>CVSROOT</i> |
| <dd> |
| This environment variable tells CVS where to find the CVS repository. |
| <p> |
| |
| <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/llvm-gcc</tt> |
| <dd> |
| This alias allows you to use the LLVM C front end without putting it in |
| your <tt>PATH</tt> or typing in its complete pathname. |
| </dl> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="unpack">Unpacking the LLVM Archives</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p> |
| If you have the LLVM distribution, you will need to unpack it before you |
| can begin to compile it. LLVM is distributed as a set of four files. Each |
| file is a TAR archive that is compressed with the gzip program. |
| </p> |
| |
| <p> The four files are the following: |
| <dl compact> |
| <dt>llvm.tar.gz |
| <dd>This is the source code to the LLVM suite. |
| <p> |
| |
| <dt>cfrontend.sparc.tar.gz |
| <dd>This is the binary release of the C front end for Solaris/Sparc. |
| <p> |
| |
| <dt>cfrontend.x86.tar.gz |
| <dd>This is the binary release of the C front end for Linux/x86. |
| <p> |
| |
| <dt>cfrontend-src.tar.gz |
| <dd>This is the source code release of the C front end. |
| <p> |
| </dl> |
| |
| <p> |
| To unpack the files, take each one, unzip it, and then untar it. A fast |
| way to do that is with the following: |
| </p> |
| |
| <tt>gunzip --stdout <i>name of file</i> | tar -xvf -</tt> |
| |
| <p> |
| For example, to extract the LLVM source code, use the following command: |
| </p> |
| |
| <tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="checkout">Checkout LLVM from CVS</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>If you have access to our CVS repository, you can get a fresh copy of |
| the entire source code. All you need to do is check it out from CVS as |
| follows: |
| <ul> |
| <li><tt>cd <i>where-you-want-llvm-to-live</i></tt> |
| <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt></p> |
| </ul> |
| |
| <p>This will create an '<tt>llvm</tt>' directory in the current |
| directory and fully populate it with the LLVM source code, Makefiles, |
| test directories, and local copies of documentation files.</p> |
| |
| <p> |
| Note that the C front end is not included in the CVS repository. You |
| should have either downloaded the source, or better yet, downloaded the |
| binary distribution for your platform. |
| </p> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="config">Local LLVM Configuration</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>Once checked out from the CVS repository, the LLVM suite source code |
| must be configured via the <tt>configure</tt> script. This script sets |
| variables in <tt>llvm/Makefile.config</tt> and |
| <tt>llvm/include/Config/config.h</tt>. |
| |
| <p> |
| The following environment variables are used by <tt>configure</tt> to |
| configure Makefile.config: |
| </p> |
| |
| <ul> |
| <p><li><i>CXX</i> = Pathname of the C++ compiler to use. |
| <p><li><i>CC</i> = Pathname of the C compiler to use. |
| </ul> |
| |
| The following options can be used to set or enable LLVM specific options: |
| |
| <dl compact> |
| <dt><i>--with-objroot=OBJ_ROOT</i> |
| <dd> |
| Path to the directory where |
| object files, libraries, and executables should be placed. |
| If this is set to <tt>.</tt>, then the object files will be placed |
| within the source code tree. If left unspecified, the default value is |
| <tt>.</tt>. |
| (See the Section on <a href=#objfiles> |
| The location for LLVM object files</a> |
| for more information.) |
| <p> |
| <dt><i>--with-llvmgccdir=LLVMGCCDIR</i> |
| <dd> |
| Path to the location where the LLVM C front end binaries and |
| associated libraries will be installed. |
| <p> |
| <dt><i>--enable-optimized</i> |
| <dd> |
| Enables optimized compilation (debugging symbols are removed and GCC |
| optimization flags are enabled). The default is to use an unoptimized |
| build (also known as a debug build). |
| <p> |
| <dt><i>--enable-jit</i> |
| <dd> |
| Compile the Just In Time (JIT) functionality. This is not available |
| on all platforms. The default is dependent on platform, so it is best |
| to explicitly enable it if you want it. |
| </dl> |
| |
| In addition to running <tt>configure</tt>, you must set the |
| <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts. |
| This environment variable is used to locate "system" libraries like |
| "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set |
| to the absolute path for the bytecode-libs subdirectory of the C front-end |
| install, or LLVMGCCDIR/llvm-gcc/bytecode-libs. For example, one might |
| set <tt>LLVM_LIB_SEARCH_PATH</tt> to |
| <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86 |
| version of the C front-end on our research machines.<p> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="compile">Compiling the LLVM Suite Source Code</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| Once you have configured LLVM, you can build it. There are three types of |
| builds: |
| |
| <dl compact> |
| <dt>Debug Builds |
| <dd> |
| These builds are the default. They compile the tools and libraries |
| with debugging information. |
| <p> |
| |
| <dt>Release (Optimized) Builds |
| <dd> |
| These builds are enabled with the <tt>--enable-optimized</tt> option to |
| <tt>configure</tt>. They compile the tools and libraries with GCC |
| optimizer flags on and strip debugging information from the libraries |
| and executables it generates. |
| <p> |
| |
| <dt>Profile Builds |
| <dd> |
| These builds are for use with profiling. They compile profiling |
| information into the code for use with programs like <tt>gprof</tt>. |
| Profile builds must be started by setting variables on the |
| <tt>make</tt> command line. |
| </dl> |
| |
| Once you have LLVM configured, you can build it by entering the top level |
| <tt>llvm</tt> directory and issuing the following command: |
| <p> |
| <tt>make</tt> |
| |
| <p> |
| If you have multiple processors in your machine, you may wish to use some |
| of the parallel build options provided by GNU Make. For example, you could |
| use the command: |
| </p> |
| |
| <p> |
| <tt>make -j2</tt> |
| |
| <p> |
| There are several other targets which are useful when working with the LLVM |
| source code: |
| |
| <dl compact> |
| <dt><tt>make clean</tt> |
| <dd> |
| Removes all files generated by the build. This includes object files, |
| generated C/C++ files, libraries, and executables. |
| <p> |
| |
| <dt><tt>make distclean</tt> |
| <dd> |
| Removes everything that <tt>make clean</tt> does, but also removes |
| files generated by <tt>configure</tt>. It attempts to return the |
| source tree to the original state in which it was shipped. |
| <p> |
| </dl> |
| |
| It is also possible to override default values from <tt>configure</tt> by |
| declaring variables on the command line. The following are some examples: |
| |
| <dl compact> |
| <dt><tt>make ENABLE_OPTIMIZED=1</tt> |
| <dd> |
| Perform a Release (Optimized) build. |
| <p> |
| |
| <dt><tt>make ENABLE_PROFILING=1</tt> |
| <dd> |
| Perform a Profiling build. |
| <p> |
| |
| <dt><tt>make VERBOSE=1</tt> |
| <dd> |
| Print what <tt>make</tt> is doing on standard output. |
| <p> |
| </dl> |
| |
| Every directory in the LLVM source tree includes a <tt>Makefile</tt> to |
| build it and any subdirectories that it contains. Entering any directory |
| inside the LLVM source tree and typing <tt>make</tt> should rebuild |
| anything in or below that directory that is out of date. |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="build">Compiling the LLVM C Front End</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <b> |
| <p> |
| This step is optional if you have the C front end binary distrubtion for |
| your platform. |
| </p> |
| </b> |
| |
| Now that you have the LLVM Suite built, you can build the C front end. For |
| those of you that have built GCC before, the process is very similar. |
| <p> |
| Be forewarned, though: the build system for the C front end is not as |
| polished as the rest of the LLVM code, so there will be many warnings and |
| errors that you will need to ignore for now: |
| |
| <ol> |
| <li>Ensure that <tt><i>OBJ_ROOT</i>/llvm/tools/Debug</tt> is at the |
| <i>end</i> of your <tt>PATH</tt> environment variable. |
| |
| <li><tt>cd <i>GCCOBJ</i></tt> |
| |
| <li>Configure the source code: |
| <ul> |
| <li>On Linux/x86, use |
| <ul> |
| <li><tt><i>GCCSRC</i>/configure --prefix=<i>LLVMGCCDIR</i> |
| --enable-languages=c</tt> |
| </ul> |
| |
| <li>On Solaris/Sparc, use |
| <ul> |
| <li><tt><i>GCCSRC</i>/configure --prefix=<i>LLVMGCCDIR</i> |
| --enable-languages=c --target=sparcv9-sun-solaris2</tt> |
| </ul> |
| </ul> |
| |
| <li><tt>make</tt> |
| |
| <li>The build will eventually fail. Don't worry; chances are good that |
| everything that needed to build is built. |
| |
| <li><tt>make -k install</tt> |
| </ol> |
| |
| At this point, you should have a working copy of the LLVM C front end |
| installed in <i>LLVMGCCDIR</i>. |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="objfiles">The location for LLVM object files</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>The LLVM build system sends most output files generated during the build |
| into the directory defined by the variable <i>OBJ_ROOT</i> in |
| <tt>llvm/Makefile.config</tt>, which is set by the <i>--with-objroot</i> |
| option in <tt>configure</tt>. This can be either just your normal LLVM |
| source tree or some other directory writable by you. You may wish to put |
| object files on a different filesystem either to keep them from being backed |
| up or to speed up local builds. |
| |
| <p> |
| If <i>OBJ_ROOT</i> is specified, then the build system will create a |
| directory tree underneath it that resembles the source code's pathname |
| relative to your home directory. |
| </p> |
| |
| <p> |
| For example, suppose that <i>OBJ_ROOT</i> is set to <tt>/tmp</tt> and the |
| LLVM suite source code is located in <tt>/usr/home/joe/src/llvm</tt>, where |
| <tt>/usr/home/joe</tt> is the home directory of a user named Joe. Then, |
| the object files will be placed in <tt>/tmp/src/llvm</tt>. |
| </p> |
| |
| <p> |
| The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories |
| named after the build type: |
| </p> |
| |
| <dl compact> |
| <dt>Debug Builds |
| <dd> |
| <dl compact> |
| <dt>Tools |
| <dd><tt><i>OBJ_ROOT</i>/llvm/tools/Debug</tt> |
| <dt>Libraries |
| <dd><tt><i>OBJ_ROOT</i>/llvm/lib/Debug</tt> |
| </dl> |
| <p> |
| |
| <dt>Release Builds |
| <dd> |
| <dl compact> |
| <dt>Tools |
| <dd><tt><i>OBJ_ROOT</i>/llvm/tools/Release</tt> |
| <dt>Libraries |
| <dd><tt><i>OBJ_ROOT</i>/llvm/lib/Release</tt> |
| </dl> |
| <p> |
| |
| <dt>Profile Builds |
| <dd> |
| <dl compact> |
| <dt>Tools |
| <dd><tt><i>OBJ_ROOT</i>/llvm/tools/Profile</tt> |
| <dt>Libraries |
| <dd><tt><i>OBJ_ROOT</i>/llvm/lib/Profile</tt> |
| </dl> |
| </dl> |
| |
| <!--=====================================================================--> |
| <center> |
| <h2><a name="layout"><b>Program Layout</b></a></h2> |
| </center> |
| <!--=====================================================================--> |
| |
| <p>One useful source of information about the LLVM source base is the LLVM <a |
| href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a |
| href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>. The |
| following is a brief introduction to code layout:</p> |
| |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| Every directory checked out of CVS will contain a <tt>CVS</tt> directory; |
| for the most part these can just be ignored. |
| |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="include"><tt>llvm/include</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| This directory contains public header files exported from the LLVM |
| library. The three main subdirectories of this directory are:<p> |
| |
| <ol> |
| <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM |
| specific header files. This directory also has subdirectories for |
| different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>, |
| <tt>Reoptimizer</tt>, <tt>Target</tt>, <tt>Transforms</tt>, etc... |
| |
| <li><tt>llvm/include/Support</tt> - This directory contains generic |
| support libraries that are independent of LLVM, but are used by LLVM. |
| For example, some C++ STL utilities and a Command Line option processing |
| library. |
| |
| <li><tt>llvm/include/Config</tt> - This directory contains header files |
| configured by the <tt>configure</tt> script. They wrap "standard" UNIX |
| and C header files. Source code can include these header files which |
| automatically take care of the conditional #includes that the configure |
| script generates. |
| </ol> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="lib"><tt>llvm/lib</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| This directory contains most of the source files of the LLVM system. In |
| LLVM almost all |
| code exists in libraries, making it very easy to share code among the |
| different <a href="#tools">tools</a>.<p> |
| |
| <dl compact> |
| <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM |
| source files that implement core classes like Instruction and BasicBlock. |
| |
| <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code |
| for the LLVM assembly language parser library. |
| |
| <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading |
| and write LLVM bytecode. |
| |
| <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C |
| converter. |
| |
| <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of |
| different program analyses, such as Dominator Information, Call Graphs, |
| Induction Variables, Interval Identification, Natural Loop Identification, |
| etc... |
| |
| <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source |
| code for the LLVM to LLVM program transformations, such as Aggressive Dead |
| Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop |
| Invarient Code Motion, Dead Global Elimination, Pool Allocation, and many |
| others... |
| |
| <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that |
| describe various target architectures for code generation. For example, |
| the llvm/lib/Target/Sparc directory holds the Sparc machine |
| description.<br> |
| |
| <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts |
| of the code generator: Instruction Selector, Instruction Scheduling, and |
| Register Allocation. |
| |
| <dt><tt>llvm/lib/Reoptimizer/</tt><dd> This directory holds code related |
| to the runtime reoptimizer framework that is currently under development. |
| |
| <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code |
| that corresponds to the header files located in |
| <tt>llvm/include/Support/</tt>. |
| </dl> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="test"><tt>llvm/test</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>This directory contains regression tests and source code that is used to |
| test the LLVM infrastructure...</p> |
| |
| <!-------------------------------------------------------------------------> |
| <h3><a name="tools"><tt>llvm/tools</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>The <b>tools</b> directory contains the executables built out of the |
| libraries above, which form the main part of the user interface. You can |
| always get help for a tool by typing <tt>tool_name --help</tt>. The |
| following is a brief introduction to the most important tools.</p> |
| |
| <dl compact> |
| <dt><tt><b>as</b></tt><dd>The assembler transforms the human readable |
| LLVM assembly to LLVM bytecode.<p> |
| |
| <dt><tt><b>dis</b></tt><dd>The disassembler transforms the LLVM bytecode |
| to human readable LLVM assembly. Additionally it can convert LLVM |
| bytecode to C, which is enabled with the <tt>-c</tt> option.<p> |
| |
| <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which |
| can directly execute LLVM bytecode (although very slowly...). In addition |
| to a simple interpreter, <tt>lli</tt> is also has debugger and tracing |
| modes (entered by specifying <tt>-debug</tt> or <tt>-trace</tt> on the |
| command line, respectively). Finally, for architectures that support it |
| (currently only x86 and Sparc), by default, <tt>lli</tt> will function as |
| a Just-In-Time compiler (if the functionality was compiled in), and will |
| execute the code <i>much</i> faster than the interpreter.<p> |
| |
| <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, |
| which translates LLVM bytecode to a SPARC or x86 assembly file.<p> |
| |
| <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC based C frontend |
| that has been retargeted to emit LLVM code as the machine code output. It |
| works just like any other GCC compiler, taking the typical <tt>-c, -S, -E, |
| -o</tt> options that are typically used. The source code for the |
| <tt>llvmgcc</tt> tool is currently not included in the LLVM cvs tree |
| because it is quite large and not very interesting.<p> |
| |
| <ol> |
| <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the |
| <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This |
| tool actually assembles LLVM assembly to LLVM bytecode, |
| performs a variety of optimizations, |
| and outputs LLVM bytecode. Thus when you invoke <tt>llvmgcc -c x.c -o |
| x.o</tt>, you are causing <tt>gccas</tt> to be run, which writes the |
| <tt>x.o</tt> file (which is an LLVM bytecode file that can be |
| disassembled or manipulated just like any other bytecode file). The |
| command line interface to <tt>gccas</tt> is designed to be as close as |
| possible to the <b>system</b> '<tt>as</tt>' utility so that the gcc |
| frontend itself did not have to be modified to interface to a "weird" |
| assembler.<p> |
| |
| <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM |
| bytecode files into one bytecode file and does some optimization. It is |
| the linker invoked by the gcc frontend when multiple .o files need to be |
| linked together. Like <tt>gccas</tt> the command line interface of |
| <tt>gccld</tt> is designed to match the system linker, to aid |
| interfacing with the GCC frontend.<p> |
| </ol> |
| |
| <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a |
| series of LLVM to LLVM transformations (which are specified on the command |
| line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>' |
| command is a good way to get a list of the program transformations |
| available in LLVM.<p> |
| |
| |
| <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific |
| analysis on an input LLVM bytecode file and print out the results. It is |
| primarily useful for debugging analyses, or familiarizing yourself with |
| what an analysis does.<p> |
| |
| </dl> |
| |
| <!--=====================================================================--> |
| <h2><a name="tutorial">An example using the LLVM tool chain</h2> |
| <!--=====================================================================--> |
| |
| <ol> |
| <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:<p> |
| |
| <tt>% llvmgcc hello.c -o hello</tt><p> |
| |
| This will create two result files: <tt>hello</tt> and |
| <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that |
| corresponds the the compiled program and the library facilities that it |
| required. <tt>hello</tt> is a simple shell script that runs the bytecode |
| file with <tt>lli</tt>, making the result directly executable.<p> |
| |
| <li>Run the program. To make sure the program ran, execute one of the |
| following commands:<p> |
| |
| <tt>% ./hello</tt><p> |
| |
| or<p> |
| |
| <tt>% lli hello.bc</tt><p> |
| |
| <li>Use the <tt>dis</tt> utility to take a look at the LLVM assembly |
| code:<p> |
| |
| <tt>% dis < hello.bc | less</tt><p> |
| |
| <li>Compile the program to native Sparc assembly using the code |
| generator (assuming you are currently on a Sparc system):<p> |
| |
| <tt>% llc hello.bc -o hello.s</tt><p> |
| |
| <li>Assemble the native sparc assemble file into a program:<p> |
| |
| <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p> |
| |
| <li>Execute the native sparc program:<p> |
| |
| <tt>% ./hello.sparc</tt><p> |
| |
| </ol> |
| |
| |
| <!--=====================================================================--> |
| <h2><a name="help">Common Problems</a></h2> |
| <!--=====================================================================--> |
| |
| Below are common problems and their remedies: |
| |
| <dl compact> |
| <dt><b>When I run configure, it finds the wrong C compiler.</b> |
| <dd> |
| The <tt>configure</tt> script attempts to locate first <tt>gcc</tt> and |
| then <tt>cc</tt>, unless it finds compiler paths set in <tt>CC</tt> and |
| <tt>CXX</tt> for the C and C++ compiler, respectively. |
| |
| If <tt>configure</tt> finds the wrong compiler, either adjust your |
| <tt>PATH</tt> environment variable or set <tt>CC</tt> and <tt>CXX</tt> |
| explicitly. |
| <p> |
| |
| <dt><b>I compile the code, and I get some error about /localhome</b>. |
| <dd> |
| There are several possible causes for this. The first is that you |
| didn't set a pathname properly when using <tt>configure</tt>, and it |
| defaulted to a pathname that we use on our research machines. |
| <p> |
| Another possibility is that we hardcoded a path in our Makefiles. If |
| you see this, please email the LLVM bug mailing list with the name of |
| the offending Makefile and a description of what is wrong with it. |
| |
| <dt><b>The <tt>configure</tt> script finds the right C compiler, but it |
| uses the LLVM linker from a previous build. What do I do?</b> |
| <dd> |
| The <tt>configure</tt> script uses the <tt>PATH</tt> to find |
| executables, so if it's grabbing the wrong linker/assembler/etc, there |
| are two ways to fix it: |
| <ol> |
| <li>Adjust your <tt>PATH</tt> environment variable so that the |
| correct program appears first in the <tt>PATH</tt>. This may work, |
| but may not be convenient when you want them <i>first</i> in your |
| path for other work. |
| <p> |
| |
| <li>Run <tt>configure</tt> with an alternative <tt>PATH</tt> that |
| is correct. In a Borne compatible shell, the syntax would be: |
| <p> |
| <tt>PATH=<the path without the bad program> ./configure ...</tt> |
| <p> |
| This is still somewhat inconvenient, but it allows |
| <tt>configure</tt> to do its work without having to adjust your |
| <tt>PATH</tt> permanently. |
| </ol> |
| </dl> |
| |
| <!--=====================================================================--> |
| <h2><a name="links">Links</a></h2> |
| <!--=====================================================================--> |
| |
| <p>This document is just an <b>introduction</b> to how to use LLVM to do |
| some simple things... there are many more interesting and complicated things |
| that you can do that aren't documented here (but we'll gladly accept a patch |
| if you want to write something up!). For more information about LLVM, check |
| out:</p> |
| |
| <ul> |
| <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li> |
| <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li> |
| <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project that Uses LLVM</a></li> |
| </ul> |
| |
| <hr> |
| |
| If you have any questions or run into any snags (or you have any |
| additions...), please send an email to |
| <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p> |
| |
| <!-- Created: Mon Jul 1 02:29:02 CDT 2002 --> |
| <!-- hhmts start --> |
| Last modified: Tue Jun 3 22:06:43 CDT 2003 |
| <!-- hhmts end --> |
| </body> |
| </html> |