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| <title>Getting Started with LLVM System</title> |
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| <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> 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> |
| <li><a href="#starting">Getting started with LLVM</a> |
| <ol> |
| <li><a href="#quickstart">Getting started quickly (a summary)</a> |
| <li><a href="#checkout">Checkout LLVM from CVS</a> |
| <li><a href="#terminology">Terminology and Notation</tt></a> |
| <li><a href="#objfiles">The location for object files</tt></a> |
| <li><a href="#config">Local Configuration Options</tt></a> |
| <li><a href="#environment">Setting up your environment</a> |
| <li><a href="#compile">Compiling the source code</a> |
| </ol> |
| <li><a href="#layout">Program layout</a> |
| <ol> |
| <li><a href="#cvsdir">CVS directories</a> |
| <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><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> |
| <!--=====================================================================--> |
| |
| <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: |
| <ul> |
| <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>Edit <tt>llvm/Makefile.config</tt> to set local paths if necessary. |
| <li><tt>cd llvm</tt> |
| <li><tt>gmake -k |& tee gnumake.out |
| # this is csh or tcsh syntax</tt> |
| </ul> |
| |
| <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>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 |
| 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>To 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> |
| |
| <!-------------------------------------------------------------------------> |
| <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): |
| |
| <ul> |
| <p><li><i>LLVM_OBJ_DIR</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><li><i>LLVMGCCDIR</i> = Path to the location of the LLVM front-end |
| binaries and associated libraries. |
| <p><li><i>BURG</i> = Path to the burg program used for instruction |
| selection. |
| <p><li><i>PURIFY</i> = Path to the purify program. |
| </ul> |
| |
| <!-------------------------------------------------------------------------> |
| <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 LLVM_OBJ_DIR in |
| <tt>llvm/Makefile.config</tt>. |
| This can be either just your normal </tt>llvm</tt> 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 you do not wish to use a different location for object files, |
| just set this variable to ".". |
| |
| <!-------------------------------------------------------------------------> |
| <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). |
| |
| <pre> |
| # Make the C front end easy to use... |
| alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt> |
| |
| # Make the LLVM tools easy to use... |
| setenv PATH <i>LLVM_OBJ_DIR</i>/tools/Debug:${PATH} |
| </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 LLVM <a href="#tools">LLVM tools</a> are part of the LLVM |
| source base, and built when compiling LLVM. They will be built into the |
| <tt><i>LLVM_OBJ_DIR</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 Makefile to build it, |
| and any subdirectories that it contains. These makefiles require that you |
| use <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>llvm/tools/Debug</tt>. If you want to look at the libraries that |
| were compiled, look in <tt>llvm/lib/Debug</tt>.</p> |
| |
| If you get an error talking about a <tt>/shared</tt> directory, 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>BUILD_ROOT=.</tt>" option enabled in the |
| <tt>Makefile.common</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> |
| |
| |
| <!-------------------------------------------------------------------------> |
| <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> |
| |
| <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 independant of LLVM, but are used by LLVM. |
| For example, some C++ STL utilities and a Command Line option processing |
| library. |
| </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> |
| |
| <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/CWrite/</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 Propogation, 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 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> |
| |
| <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, |
| which translates LLVM bytecode to a SPARC 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 "wierd" |
| 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:<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="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://tank.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:hldnbrnd@uiuc.edu">Nicholas Hildenbrandt</a> or |
| <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p> |
| |
| <!-- Created: Mon Jul 1 02:29:02 CDT 2002 --> |
| <!-- hhmts start --> |
| Last modified: Tue Aug 13 16:09:25 CDT 2002 |
| <!-- hhmts end --> |
| </body> |
| </html> |