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| <title>Getting Started with LLVM System</title> |
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| <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> and <a |
| href="http://www.cs.uiuc.edu/%7Evadve">Vikram Adve</a> </font></h1> |
| </center> |
| <!--=====================================================================--> |
| |
| <h2><a name="Contents">Contents</a></h2> |
| <!--=====================================================================--> |
| |
| <ul> |
| <li><a href="#overview">Overview</a> </li> |
| <li><a href="#starting">Getting started with LLVM</a> |
| <ol> |
| <li><a href="#quickstart">Getting started quickly (a summary)</a> |
| </li> |
| <li><a href="#checkout">Checkout LLVM from CVS</a> </li> |
| <li><a href="#terminology">Terminology and Notation</a> </li> |
| <li><a href="#objfiles">The location for object files</a> </li> |
| <li><a href="#config">Local Configuration Options</a> </li> |
| <li><a href="#environment">Setting up your environment</a> |
| </li> |
| <li><a href="#compile">Compiling the source code</a> </li> |
| </ol> |
| </li> |
| <li><a href="#layout">Program layout</a> |
| <ol> |
| <li><a href="#cvsdir">CVS directories</a> </li> |
| <li><a href="#dd"><tt>Depend</tt>, <tt>Debug</tt>, & |
| <tt>Release</tt> directories</a></li> |
| <li><a href="#include"><tt>llvm/include</tt></a> </li> |
| <li><a href="#lib"><tt>llvm/lib</tt></a> </li> |
| <li><a href="#test"><tt>llvm/test</tt></a> </li> |
| <li><a href="#tools"><tt>llvm/tools</tt></a> </li> |
| </ol> |
| </li> |
| <li><a href="#tutorial">An example using the LLVM tool chain</a> |
| </li> |
| <li><a href="#links">Links</a> </li> |
| </ul> |
| <!--=====================================================================--> |
| |
| <center> |
| <h2><a name="overview"><b>Overview</b></a></h2> |
| </center> |
| <!--=====================================================================--> |
| |
| <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> |
| <p>The later sections of this guide describe the <a href="" #layout="">general |
| layout</a> of 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. <!--=====================================================================--> |
| </p> |
| <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>Find the path to the CVS repository containing LLVM (we'll call |
| this <i>CVSROOTDIR</i>). </li> |
| <li><tt>cd <i>where-you-want-llvm-to-live</i></tt> </li> |
| <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt> </li> |
| <li><tt>cd llvm</tt> </li> |
| <li>Edit <tt>Makefile.config</tt> to set local paths. This includes |
| setting the install location of the C frontend and the various paths |
| to the C and C++ compilers used to build LLVM itself. </li> |
| <li>Set your LLVM_LIB_SEARCH_PATH environment variable. </li> |
| <li><tt>gmake -k |& tee gnumake.out # this is |
| csh or tcsh syntax</tt> </li> |
| </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. <!-------------------------------------------------------------------------> |
| </p> |
| <h3><a name="terminology">Terminology and Notation</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>Through 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> |
| |
| <ul> |
| |
| </ul> |
| <!-------------------------------------------------------------------------> |
| |
| <h3><a name="checkout">Checkout LLVM from CVS</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>Before checking out the source code, you will need to know the path to |
| the CVS repository containing LLVM source code (we'll call this <i>CVSROOTDIR</i> |
| below). Ask the person responsible for your local LLVM installation |
| to give you this path. </p> |
| <p>To get a fresh copy of the entire source code, all you need to do |
| is check it out from CVS as follows: </p> |
| <ul> |
| <li><tt>cd <i>where-you-want-llvm-to-live</i></tt> </li> |
| <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt> |
| <p></p> |
| </li> |
| </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> |
| <!-------------------------------------------------------------------------> |
| |
| <h3><a name="config">Local Configuration Options</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>The file <tt>llvm/Makefile.config</tt> defines the following path |
| variables which are specific to a particular installation of LLVM. |
| These should need to be modified only once after checking out a copy |
| of LLVM (if the default values do not already match your system): |
| </p> |
| <ul> |
| |
| <p></p> |
| <li><i>CXX</i> = Path to C++ compiler to use. |
| <p></p> |
| </li> |
| <li><i>OBJ_ROOT</i> = Path to the llvm directory where object files |
| should be placed. (See the Section on <a href="#objfiles"> The |
| location for LLVM object files</a> for more information.) |
| <p></p> |
| </li> |
| <li><i>LLVMGCCDIR</i> = Path to the location of the LLVM front-end |
| binaries and associated libraries. |
| <p></p> |
| </li> |
| <li><i>PURIFY</i> = Path to the purify program. </li> |
| </ul> |
| In addition to settings in this file, you must set a <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. For example, |
| <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> is used |
| for the X86 version of the C front-end on our research machines. |
| <p> <!-------------------------------------------------------------------------> |
| </p> |
| <h3><a name="objfiles">The location for LLVM object files</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>The LLVM make system sends most output files generated during the build |
| into the directory defined by the variable OBJ_ROOT in <tt>llvm/Makefile.config</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> |
| <p>If you do not wish to use a different location for object files (i.e. |
| building into the source tree directly), just set this variable to ".".</p> |
| <p> <!-------------------------------------------------------------------------> |
| </p> |
| <h3><a name="environment">Setting up your environment</a></h3> |
| <!-------------------------------------------------------------------------> |
| <i>NOTE: This step is optional but will set up your environment so you |
| can use the compiled LLVM tools with as little hassle as possible.</i>) |
| |
| <p>Add the following lines to your <tt>.cshrc</tt> (or the corresponding |
| lines to your <tt>.profile</tt> if you use a bourne shell derivative). |
| </p> |
| <pre> # Make the C front end easy to use...<br> alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/llvm-gcc</tt> |
| |
| # Make the LLVM tools easy to use... |
| setenv PATH <i>OBJ_ROOT</i>/llvm/tools/Debug:${PATH}<br> </pre> |
| The <tt>llvmgcc</tt> alias is useful because the C compiler is not |
| included in the CVS tree you just checked out. |
| <p>The other <a href="#tools">LLVM tools</a> are part of the LLVM source |
| base and are built when compiling LLVM. They will be built into the |
| <tt><i>OBJ_ROOT</i>/tools/Debug</tt> directory.</p> |
| <!-------------------------------------------------------------------------> |
| |
| <h3><a name="compile">Compiling the source code</a></h3> |
| <!-------------------------------------------------------------------------> |
| |
| <p>Every directory in the LLVM source tree includes a <tt>Makefile</tt> to |
| build it and any subdirectories that it contains. These makefiles require |
| GNU Make (<tt>gmake)</tt> instead of <tt>make</tt> to build them, but |
| can otherwise be used freely. To build the entire LLVM system, just |
| enter the top level <tt>llvm</tt> directory and type <tt>gmake</tt>. |
| A few minutes later you will hopefully have a freshly compiled toolchain |
| waiting for you in <tt><i>OBJ_ROOT</i></tt><tt>/llvm/tools/Debug</tt>. |
| If you want to look at the libraries that were compiled, look in <tt><i>OBJ_ROOT</i></tt><tt>/llvm/lib/Debug</tt>.</p> |
| If you get an error about the <tt>/localhome</tt> directory, chances |
| are good that something has been misconfigured. Follow the instructions |
| in the section about <a href="#environment">Setting Up Your Environment.</a> |
| <!--=====================================================================--> |
| |
| <center> |
| <h2><a name="layout"><b>Program Layout</b></a></h2> |
| </center> |
| <!--=====================================================================--> |
| |
| <p>One useful source of infomation about the LLVM sourcebase 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="ddr"><tt>Depend</tt>, <tt>Debug</tt>, & <tt>Release</tt> |
| directories</a></h3> |
| <!-------------------------------------------------------------------------> |
| If you are building with the "<tt>OBJ_ROOT=.</tt>" option enabled in |
| the <tt>Makefile.config</tt> file, most source directories will contain |
| two directories, <tt>Depend</tt> and <tt>Debug</tt>. The <tt>Depend</tt> |
| directory contains automatically generated dependance files which are |
| used during compilation to make sure that source files get rebuilt if |
| a header file they use is modified. The <tt>Debug</tt> directory holds |
| the object files, library files, and executables that are used for building |
| a debug enabled build. The <tt>Release</tt> directory is created to |
| hold the same files when the <tt>ENABLE_OPTIMIZED=1</tt> flag is passed |
| to <tt>gmake</tt>, causing an optimized built to be performed. |
| <p> <!-------------------------------------------------------------------------> |
| </p> |
| <h3><a name="include"><tt>llvm/include</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| This directory contains public header files exported from the LLVM |
| library. The two main subdirectories of this directory are: |
| <p> </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> |
| <li><tt>llvm/include/Support</tt> - This directory contains generic |
| support libraries that are independant of LLVM, but are used by LLVM. |
| For example, some C++ STL utilities and a Command Line option processing |
| library. </li> |
| </ol> |
| <!-------------------------------------------------------------------------> |
| |
| <h3><a name="lib"><tt>llvm/lib</tt></a></h3> |
| <!-------------------------------------------------------------------------> |
| This directory contains most source files of 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> </p> |
| <dl compact="compact"> |
| <dt><tt>llvm/lib/VMCore/</tt></dt> |
| <dd> This directory holds the core LLVM source files that implement |
| core classes like Instruction and BasicBlock. </dd> |
| <dt><tt>llvm/lib/AsmParser/</tt></dt> |
| <dd> This directory holds the source code for the LLVM assembly language |
| parser library. </dd> |
| <dt><tt>llvm/lib/ByteCode/</tt></dt> |
| <dd> This directory holds code for reading and write LLVM bytecode. |
| </dd> |
| <dt><tt>llvm/lib/CWriter/</tt></dt> |
| <dd> This directory implements the LLVM to C converter. </dd> |
| <dt><tt>llvm/lib/Analysis/</tt></dt> |
| <dd> This directory contains a variety of different program analyses, |
| such as Dominator Information, Call Graphs, Induction Variables, Interval |
| Identification, Natural Loop Identification, etc... </dd> |
| <dt><tt>llvm/lib/Transforms/</tt></dt> |
| <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... |
| </dd> |
| <dt><tt>llvm/lib/Target/</tt></dt> |
| <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> |
| </dd> |
| <dt><tt>llvm/lib/CodeGen/</tt></dt> |
| <dd> This directory contains the major parts of the code generator: |
| Instruction Selector, Instruction Scheduling, and Register Allocation. |
| </dd> |
| <dt><tt>llvm/lib/Reoptimizer/</tt></dt> |
| <dd> This directory holds code related to the runtime reoptimizer |
| framework that is currently under development. </dd> |
| <dt><tt>llvm/lib/Support/</tt></dt> |
| <dd> This directory contains the source code that corresponds to |
| the header files located in <tt>llvm/include/Support/</tt>. </dd> |
| </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="compact"> |
| <dt><tt><b>as</b></tt></dt> |
| <dd>The assembler transforms the human readable LLVM assembly to |
| LLVM bytecode. |
| <p> </p> |
| </dd> |
| <dt><tt><b>dis</b></tt></dt> |
| <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> </p> |
| </dd> |
| <dt><tt><b>lli</b></tt></dt> |
| <dd> <tt>lli</tt> is the LLVM interpreter, which can directly execute |
| LLVM bytecode (although very slowly...). In addition to a simple intepreter, |
| <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). |
| <p> </p> |
| </dd> |
| <dt><tt><b>llc</b></tt></dt> |
| <dd> <tt>llc</tt> is the LLVM backend compiler, which translates |
| LLVM bytecode to a SPARC assembly file. |
| <p> </p> |
| </dd> |
| <dt><tt><b>llvmgcc</b></tt></dt> |
| <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> </p> |
| <ol> |
| <dt><tt><b>gccas</b></tt></dt> |
| <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 "wierd" assembler. |
| <p> </p> |
| </dd> |
| <dt><tt><b>gccld</b></tt></dt> |
| <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> </p> |
| </dd> |
| </ol> |
| </dd> |
| <dt><tt><b>opt</b></tt></dt> |
| <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> </p> |
| </dd> |
| <dt><tt><b>analyze</b></tt></dt> |
| <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> </p> |
| </dd> |
| </dl> |
| <!--=====================================================================--> |
| |
| <h2><a name="tutorial">An example using the LLVM tool chain</a></h2> |
| <a name="tutorial"> <!--=====================================================================--> |
| </a> |
| <ol> |
| <a name="tutorial"> <li>First, create a simple C file, name it 'hello.c': |
| |
| <pre> #include <stdio.h><br> int main() {<br> printf("hello world\n");<br> return 0;<br> }<br> </pre> |
| </li> |
| <li>Next, compile the C file into a LLVM bytecode file: |
| <p> <tt>% llvmgcc hello.c -o hello</tt></p> |
| <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> |
| <p> </p> |
| </li> |
| <li>Run the program. To make sure the program ran, execute one of the |
| following commands: |
| <p> <tt>% ./hello</tt></p> |
| <p> or</p> |
| <p> <tt>% lli hello.bc</tt></p> |
| <p> </p> |
| </li> |
| <li>Use the <tt>dis</tt> utility to take a look at the LLVM assembly |
| code: |
| <p> <tt>% dis < hello.bc | less</tt></p> |
| <p> </p> |
| </li> |
| <li>Compile the program to native Sparc assembly using the code generator: |
| <p> <tt>% llc hello.bc -o hello.s</tt></p> |
| <p> </p> |
| </li> |
| <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> |
| <p> </p> |
| </li> |
| <li>Execute the native sparc program: |
| <p> <tt>% ./hello.sparc</tt></p> |
| <p> </p> |
| </li> |
| </a> |
| </ol> |
| <a name="tutorial"> <!--=====================================================================--> |
| </a> |
| <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> |
| |
| </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></p> |
| <!-- Created: Mon Jul 1 02:29:02 CDT 2002 --> <!-- hhmts start --> |
| Last modified: Tue Jun 3 22:06:43 CDT 2003 <!-- hhmts end --> <br> |
| </body> |
| </html> |