X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FGettingStarted.html;h=d23ac921302323008066109b51c38c6c44f5760d;hb=d9eceee053d20451a804c248ef71ed8a28297d94;hp=633b1e84a5d2c71819e9ae21d4815d22febfd9a8;hpb=a8f5de39426fb0d2617094960b2a126356bf32c8;p=oota-llvm.git diff --git a/docs/GettingStarted.html b/docs/GettingStarted.html index 633b1e84a5d..d23ac921302 100644 --- a/docs/GettingStarted.html +++ b/docs/GettingStarted.html @@ -1,1151 +1,1484 @@ - + - - Getting Started with LLVM System - + + + Getting Started with LLVM System + + + + +
+ Getting Started with the LLVM System +
+ + + +
+

Written by: John Criswell, - Misha Brukman, and - Vikram Adve - - - -

Contents

- - - - - - -
-

Overview

-
- - - 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 - 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 C front end. -

- The second piece is the C 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 from the LLVM suite. - - -

Requirements

- - - 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. - - -

Hardware

- - LLVM is known to work on the following platforms: - - -

- If you want to compile your own version of the C front end, you will need - additional disk space: -

- - - -

- LLVM may 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. -

- - -

Software

- -

- - Unpacking the distribution requires the following tools: -

-
GNU Zip (gzip) -
GNU Tar -
- These tools are needed to uncompress and unarchive the software. - Regular Solaris tar may work for unpacking the TAR archive but - is untested. -
- - Compiling LLVM requires that you have several different software packages - installed: - -
-
GCC -
- 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. - -

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

- -
GNU Make -
- The LLVM build system relies upon GNU Make extensions. Therefore, you - will need GNU Make (sometimes known as gmake) to build LLVM. -

- -

Flex and Bison -
- The LLVM source code is built using flex and bison. You will not be - able to configure and compile LLVM without them. -

- -

GNU M4 -
- If you are installing Bison on your machine for the first time, you - will need GNU M4 (version 1.4 or higher). -
- -

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

- - - - -

The next section 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 first subsection gives - a short summary for those who are already familiar with the system and - want to get started as quickly as possible. - -

The later sections of this guide describe the general layout of the the LLVM source-tree, a simple example using the LLVM tool chain, and links to find more information about LLVM or to get - help via e-mail. - - -

-

Getting Started with LLVM

-
- - - -

Getting Started Quickly (A Summary)

- - - Here's the short story for getting up and running quickly with LLVM: + Chris Lattner, + Misha Brukman, + Vikram Adve, and + Guochun Shi. +

+
+ + + +
+ Overview +
+ + +
+ +

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 +contains all of the tools, libraries, and header files needed to use the low +level virtual machine. It contains an assembler, disassembler, bytecode +analyzer, and bytecode optimizer. It also contains a test suite that can be +used to test the LLVM tools and the GCC front end.

+ +

The second piece is the GCC front end. This component provides a version of +GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC 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 +from the LLVM suite.

+ +

+There is a third, optional piece called llvm-test. It is a suite of programs +with a testing harness that can be used to further test LLVM's functionality +and performance. +

+ +
+ + +
+ Getting Started Quickly (A Summary) +
+ + +
+ +

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

+ +
    +
  1. Read the documentation.
    2. +
  2. Read the documentation.
    3. +
  3. Remember that you were warned twice about reading the documentation.
    4. +
  4. Install the GCC front end:
      -
    1. Install the C front end: -
        -
      1. cd where-you-want-the-C-front-end-to-live -
      2. gunzip --stdout cfrontend.platform.tar.gz | tar -xvf - - -
      - -

      - -

    2. Get the Source Code -
        -
      • With the distributed files: -
          -
        1. cd where-you-want-llvm-to-live -
        2. gunzip --stdout llvm.tar.gz | tar -xvf - -
        3. gunzip --stdout cfrontend.platform.tar.gz | tar - -xvf - -
        4. cd llvm -
        - -

        - -

      • With anonymous CVS access: -
          -
        1. Find the path to the CVS repository containing LLVM (we'll - call this CVSROOTDIR). -
        2. cd where-you-want-llvm-to-live -
        3. cvs -d CVSROOTDIR checkout llvm -
        4. cd llvm -
        -
      - - -

      - -

    3. Configure the LLVM Build Environment -
        -
      1. Run configure to configure the Makefiles and header - files for the default platform. - Useful options include: -
          -
        • --with-objroot=directory -
          - Specify where object files should be placed during the - build. - -
        • --with-llvmgccdir=directory -
          - Specify where the LLVM C frontend is going to be installed. -
        -
      - -

      - -

    4. Build the LLVM Suite -
        -
      1. Set your LLVM_LIB_SEARCH_PATH environment variable. -
      2. gmake -k |& tee gnumake.out -    # this is csh or tcsh syntax -
      - -

      - -

    - -

    See Setting Up Your Environment 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 Program Layout to learn about the - layout of the source code tree. For information on building the C front - end yourself, see Compiling the LLVM C Front End for - information. - - -

    Terminology and Notation

    - - -

    Throughout this manual, the following names are used to denote paths - specific to the local system and working environment. These are not - environment variables you need to set but just strings used in the rest - of this document below. 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:

    -
    -
    CVSROOTDIR -
    - 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. -

    - -

    OBJ_ROOT -
    - This is the top level directory for where the LLVM suite object files - will be placed during the build. -

    - -

    LLVMGCCDIR -
    - 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. -

    - For the pre-built C front end binaries, the LLVMGCCDIR is - cfrontend/platform/llvm-gcc. - -

    GCCSRC -
    - This is the pathname of the directory where the LLVM C front end source - code can be found. -

    - -

    GCCOBJ -
    - 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. -
    - - -

    Setting Up Your Environment

    - - -

    - 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 - .cshrc or .profile. - -

    -
    LLVM_LIB_SEARCH_PATH=LLVMGCCDIR/llvm-gcc/bytecode-libs -
    - This environment variable helps the LLVM C front end find bytecode - libraries that it will need for compilation. -

    - -

    alias llvmgcc LLVMGCCDIR/bin/llvm-gcc -
    - This alias allows you to use the LLVM C front end without putting it in - your PATH or typing in its complete pathname. -
    - - -

    Unpacking the LLVM Archives

    - +
  5. cd where-you-want-the-C-front-end-to-live +
  6. gunzip --stdout cfrontend.platform.tar.gz | tar -xvf - +
  7. Sparc and MacOS X Only:
    + cd cfrontend/platform
    + ./fixheaders     +
+ +
  • Get the Source Code +
    • + +
  • Configure the LLVM Build Environment +
      +
    1. Change directory to where you want to store the LLVM object + files and run configure to configure the Makefiles and + header files for the default platform. Useful options include: +
        +
      • --with-llvmgccdir=directory +

        Specify the full pathname of where the LLVM GCC frontend is + installed.

        • +
      • --enable-spec2000=directory +

        Enable the SPEC2000 benchmarks for testing. The SPEC2000 + benchmarks should be available in + directory.

        • +
      +
    • + +
  • Build the LLVM Suite: +
      +
    1. Set your LLVM_LIB_SEARCH_PATH environment variable.
      2. +
    2. gmake -k |& tee gnumake.out +    # this is csh or tcsh syntax
      3. +
    3. If you get an "internal compiler error (ICE)" see below.
      4. +
    + + + +

    Consult the Getting Started with LLVM section for +detailed information on configuring and compiling LLVM. See Setting Up Your Environment for tips that simplify +working with the GCC front end and LLVM tools. Go to Program +Layout to learn about the layout of the source code tree.

    + +
    • + + +
    + Requirements +
    + + +
    + +

    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.

    + +
    + + +
    + Hardware +
    + +
    + +

    LLVM is known to work on the following platforms:

    + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
    OSArchCompilers
    Linuxx861GCC
    SolarisV9 (Ultrasparc)GCC
    FreeBSDx861GCC
    MacOS X2PowerPCGCC
    Cygwin/Win32x861GCC
    + +

    LLVM has partial support for the following platforms:

    + + + + + + + + + + + + + + + + + + + + + +
    OSArchCompilers
    Windowsx861Visual Studio .NET4,5, MinGW
    AIX3,4PowerPCGCC
    Linux3,5PowerPCGCC
    + +

    +Notes:
    +1 Code generation supported for Pentium processors and up
    +2 Code generation supported for 32-bit ABI only
    +3 No native code generation
    +4 Build is not complete: one or more tools don't link
    +5 The GCC-based C/C++ frontend does not build
    +

    + +

    Note that you will need about 1-3 GB of space for a full LLVM build in Debug +mode, depending on the system (because of all the debug info), and the libraries +appear in more than one of the tools that get linked, so there is some +duplication. If you do not need many of the tools and you are space-conscious, +you can disable them individually in llvm/tools/Makefile. The Release +build requires considerably less space.

    + +

    The LLVM suite may compile on other platforms, but it is not +guaranteed to do so. If compilation is successful, the LLVM utilities should be +able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code +generation should work as well, although the generated native code may not work +on your platform.

    + +

    The GCC front end is not very portable at the moment. If you want to get it +to work on another platform, you can download a copy of the source and try to compile it on your platform.

    + +
    + + +
    Software
    +
    +

    Compiling LLVM requires that you have several software packages + installed. The table below lists those required packages. The Package column + is the usual name for the software package that LLVM depends on. The Version + column provides "known to work" versions of the package. The Notes column + describes how LLVM uses the package and provides other details.

    + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
    PackageVersionNotes
    GNU Make3.79, 3.79.1Makefile/build processor
    GCC3.4.2C/C++ compiler (Note 3)
    Flex2.5.4LEX compiler
    Bison1.35YACC compiler
    DejaGnu1.4.2Automated test suite (Note 2)
    tcl8.3, 8.4Automated test suite (Note 2)
    expect5.38.0Automated test suite (Note 2)
    GNU M4 + 1.4Macro processor for configuration (Note 1)
    GNU Autoconf2.59Configuration script builder (Note 1)
    GNU Automake2.59aclocal macro generator (Note 1)
    perl>5.6.0Nightly tester, utilities
    libtool1.5.10Shared library manager (Note 1)
    CVS>1.11CVS access to LLVM (Note 4)
    + +

    Notes:

    +
      +
    1. If you want to make changes to the configure scripts, + you will need GNU autoconf (2.59), and consequently, GNU M4 (version 1.4 + or higher). You will also need automake. We only use aclocal from that + package.
      2. +
    2. Only needed if you want to run the automated test + suite in the test directory.
      3. + +
    3. Only the C and C++ languages are needed so there's no + need to build the other languages for LLVM's purposes. See + below for specific version info. +
      4. +
    4. You only need CVS if you intend to build from the + latest LLVM sources. If you're working from a release distribution, you + don't need CVS.
      5. +
    +

    Additionally, your compilation host is expected to have the usual + plethora of Unix utilities. Specifically:

    + +
    + + +
    + Broken versions of GCC +
    + +
    + +

    LLVM is very demanding of the host C++ compiler, and as such tends to expose +bugs in the compiler. In particular, several versions of GCC crash when trying +to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success +with them. Other versions of GCC will probably work as well. GCC versions listed +here are known to not work. If you are using one of these versions, please try +to upgrade your GCC to something more recent. If you run into a problem with a +version of GCC not listed here, please let +us know. Please use the "gcc -v" command to find out which version +of GCC you are using. +

    + +

    GCC versions prior to 3.0: GCC 2.96.x and before had several +problems in the STL that effectively prevent it from compiling LLVM. +

    + +

    GCC 3.2.2: This version of GCC fails to compile LLVM.

    + +

    GCC 3.3.2: This version of GCC suffered from a serious bug which causes it to crash in +the "convert_from_eh_region_ranges_1" GCC function.

    +
    + + + + +
    + Getting Started with LLVM +
    + + +
    + +

    The remainder 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 later sections of this guide describe the general layout of the the LLVM source tree, a simple example using the LLVM tool chain, and links to find more information about LLVM or to get +help via e-mail.

    +
    + + +
    + Terminology and Notation +
    + +
    + +

    Throughout this manual, the following names are used to denote paths +specific to the local system and working environment. These are not +environment variables you need to set but just strings used in the rest +of this document below. 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:

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

    - 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. -

    - -

    The four files are as follows: -

    -
    llvm.tar.gz -
    This is the source code to the LLVM suite. -

    - -

    cfrontend.sparc.tar.gz -
    This is the binary release of the C front end for Solaris/Sparc. -

    - -

    cfrontend.x86.tar.gz -
    This is the binary release of the C front end for Linux/x86. -

    - -

    cfrontend-src.tar.gz -
    This is the source code release of the C front end. -

    -

    - - -

    Checkout LLVM from CVS

    - - -

    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: -

      -
    • cd where-you-want-llvm-to-live -
    • cvs -d CVSROOTDIR checkout llvm

      -
    - -

    This will create an 'llvm' directory in the current - directory and fully populate it with the LLVM source code, Makefiles, - test directories, and local copies of documentation files.

    +
    OBJ_ROOT +
    + This is the top level directory of the LLVM object tree (i.e. the + tree where object files and compiled programs will be placed. It + can be the same as SRC_ROOT).

    - 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. -

    - - -

    Install the C Front End

    - +
    LLVMGCCDIR +
    + This is the where the LLVM GCC Front End is installed.

    - Before configuring and compiling the LLVM suite, it is best to extract the - LLVM C front end. While not used in building, the C front end is used by - the LLVM test suite, and its location must be given to the - configure script before the LLVM suite can be built. -

    + For the pre-built GCC front end binaries, the LLVMGCCDIR is + cfrontend/platform/llvm-gcc. +
    -

    - To install the C front end, do the following: -

      -
    1. cd where-you-want-the-front-end-to-live -
    2. gunzip --stdout cfrontend.platform.tar.gz | tar -xvf - - -
    +
    - -

    Local LLVM Configuration

    - + +
    + Setting Up Your Environment +
    -

    Once checked out from the CVS repository, the LLVM suite source code - must be configured via the configure script. This script sets - variables in llvm/Makefile.config and - llvm/include/Config/config.h. +

    -

    - The following environment variables are used by the configure - script to configure the build system: -

    - - - - - - - - - - - - - - - - -
    Variable - Purpose -
    CC - Tells configure which C compiler to use. By default, - configure will look for the first GCC compiler in - PATH. Use this variable to override - configure's default behavior. -
    CXX - Tells configure which C++ compiler to use. By default, - configure will look for the first GCC compiler in - PATH. Use this variable to override - configure's default behavior. -
    +

    +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 +.cshrc or .profile. +

    +
    LLVM_LIB_SEARCH_PATH=LLVMGCCDIR/bytecode-libs +
    + This environment variable helps the LLVM GCC front end find bytecode + libraries that it will need for compilation.

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

    -
    -
    --with-objroot=OBJ_ROOT -
    - Path to the directory where - object files, libraries, and executables should be placed. - If this is set to ., then the object files will be placed - within the source code tree. If left unspecified, the default value is - the following: -
      -
    • - If the USER environment variable is specified and the directory - /localhome/$USER exists, then the default value is - /localhome/$USER. - -
    • - Otherwise, the default value is .. -
    - (See the Section on - The Location of LLVM Object Files - for more information.) -

    -

    --with-llvmgccdir=LLVMGCCDIR -
    - Path to the location where the LLVM C front end binaries and - associated libraries will be installed. -

    -

    --enable-optimized -
    - 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). -

    -

    --enable-jit +
    alias llvmgcc LLVMGCCDIR/bin/gcc +
    alias llvmg++ LLVMGCCDIR/bin/g++
    - 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. -
    + These aliases allow you to use the LLVM C and C++ front ends without putting + them in your PATH or typing in their complete pathnames. +
    + +
    + + +
    + Unpacking the LLVM Archives +
    - In addition to running configure, you must set the - LLVM_LIB_SEARCH_PATH environment variable in your startup scripts. - This environment variable is used to locate "system" libraries like - "-lc" and "-lm" 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 LLVM_LIB_SEARCH_PATH to - /home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs for the X86 - version of the C front-end on our research machines.

    - - -

    Compiling the LLVM Suite Source Code

    - - - Once you have configured LLVM, you can build it. There are three types of - builds: - -
    -
    Debug Builds -
    - These builds are the default. They compile the tools and libraries - with debugging information. -

    - -

    Release (Optimized) Builds -
    - These builds are enabled with the --enable-optimized option to - configure. They compile the tools and libraries with GCC - optimizer flags on and strip debugging information from the libraries - and executables it generates. -

    - -

    Profile Builds -
    - These builds are for use with profiling. They compile profiling - information into the code for use with programs like gprof. - Profile builds must be started by setting variables on the - gmake command line. -
    +
    + +

    +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 two files: the LLVM +suite and the LLVM GCC front end compiled for your platform. Each +file is a TAR archive that is compressed with the gzip program. +

    + +

    The files are as follows: +

    +
    llvm-1.4.tar.gz
    +
    This is the source code for the LLVM libraries and tools.
    + +
    llvm-test-1.4.tar.gz
    +
    This is the source code for the LLVM test suite.
    + +
    cfrontend-1.4.source.tar.gz
    +
    This is the source release of the GCC front end.
    + +
    cfrontend-1.4.sparc-sun-solaris2.8.tar.gz
    +
    This is the binary release of the GCC front end for Solaris/Sparc. +
    - Once you have LLVM configured, you can build it by entering the top level - llvm directory and issuing the following command: -

    - gmake +

    cfrontend-1.4.i686-redhat-linux-gnu.tar.gz
    +
    This is the binary release of the GCC front end for Linux/x86.
    + +
    cfrontend-1.4.i386-unknown-freebsd5.1.tar.gz
    +
    This is the binary release of the GCC front end for FreeBSD/x86.
    + +
    cfrontend-1.4.powerpc-apple-darwin7.0.0.tar.gz
    +
    This is the binary release of the GCC front end for MacOS X/PPC.
    +
    + +
    -

    - 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: -

    + +
    + Checkout LLVM from CVS +
    + +
    + +

    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:

    -

    - gmake -j2 +

    -

    - There are several other targets which are useful when working with the LLVM - source code: - -

    -
    gmake clean -
    - Removes all files generated by the build. This includes object files, - generated C/C++ files, libraries, and executables. -

    - -

    gmake distclean -
    - Removes everything that gmake clean does, but also removes - files generated by configure. It attempts to return the - source tree to the original state in which it was shipped. -

    -

    +

    This will create an 'llvm' directory in the current +directory and fully populate it with the LLVM source code, Makefiles, +test directories, and local copies of documentation files.

    - It is also possible to override default values from configure by - declaring variables on the command line. The following are some examples: +

    If you want to get a specific release (as opposed to the most recent +revision), you can specify a label. The following releases have the following +label:

    -
    -
    gmake ENABLE_OPTIMIZED=1 -
    - Perform a Release (Optimized) build. -

    +

      +
    • Release 1.4: RELEASE_14
      • +
    • Release 1.3: RELEASE_13
      • +
    • Release 1.2: RELEASE_12
      • +
    • Release 1.1: RELEASE_11
      • +
    • Release 1.0: RELEASE_1
      • +
    + +

    If you would like to get the LLVM test suite (a separate package as of 1.4), +you get it from the CVS repository:

    +
    +  cd llvm/projects
+  cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-test
+
    +

    By placing it in the llvm/projects, it will be automatically +configured by the LLVM configure script as well as automatically updated when +you run cvs update.

    + +

    If you would like to get the GCC front end source code, you can also get it +from the CVS repository:

    + +
    +  cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
+
    + +

    Please note that you must follow these +instructions to successfully build the LLVM GCC front-end.

    + +
    + + +
    + LLVM CVS Mirrors +
    + +
    + +

    If the main CVS server is overloaded or inaccessible, you can try one of +these user-hosted mirrors:

    + + +
    + + +
    + Install the GCC Front End +
    + +
    + +

    Before configuring and compiling the LLVM suite, you need to extract the LLVM +GCC front end from the binary distribution. It is used for building the +bytecode libraries later used by the GCC front end for linking programs, and its +location must be specified when the LLVM suite is configured.

    + +

    To install the GCC front end, do the following:

    + +
      +
    1. cd where-you-want-the-front-end-to-live
      2. +
    2. gunzip --stdout cfrontend-version.platform.tar.gz | tar -xvf + -
      3. +
    + +

    If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the +header files:

    + +

    cd cfrontend/platform
    + ./fixheaders

    + +

    The binary versions of the GCC front end may not suit all of your needs. For +example, the binary distribution may include an old version of a system header +file, not "fix" a header file that needs to be fixed for GCC, or it may be +linked with libraries not available on your system.

    + +

    In cases like these, you may want to try building the GCC front end from source. This is +not for the faint of heart, so be forewarned.

    + +
    + + +
    + Local LLVM Configuration +
    + +
    + +

    Once checked out from the CVS repository, the LLVM suite source code must be +configured via the configure script. This script sets variables in the +various *.in files, most notably llvm/Makefile.config and +llvm/include/Config/config.h. It also populates OBJ_ROOT with +the Makefiles needed to begin building LLVM.

    + +

    The following environment variables are used by the configure +script to configure the build system:

    + + + + + + + + + + + +
    VariablePurpose
    CCTells configure which C compiler to use. By default, + configure will look for the first GCC C compiler in + PATH. Use this variable to override + configure's default behavior.
    CXXTells configure which C++ compiler to use. By default, + configure will look for the first GCC C++ compiler in + PATH. Use this variable to override + configure's default behavior.
    + +

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

    + +
    +
    --with-llvmgccdir=LLVMGCCDIR
    +
    + Path to the location where the LLVM GCC front end binaries and + associated libraries were installed. This must be specified as an + absolute pathname. +

    +
    +
    --with-tclinclude
    +
    Path to the tcl include directory under which the tclsh can be + found. Use this if you have multiple tcl installations on your machine and you + want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the + dejagnu based test suite in llvm/test. If you don't specify this + option, the LLVM configure script will search for tcl 8.4 and 8.3 releases. +

    +
    +
    --enable-optimized
    +
    + Enables optimized compilation by default (debugging symbols are removed + and GCC optimization flags are enabled). The default is to use an + unoptimized build (also known as a debug build). +

    +
    +
    --enable-jit
    +
    + Compile the Just In Time (JIT) compiler 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. +

    +
    +
    --enable-doxygen
    +
    Look for the doxygen program and enable construction of doxygen based + documentation from the source code. This is disabled by default because + generating the documentation can take a long time and producess 100s of + megabytes of output.
    +
    + +

    To configure LLVM, follow these steps:

    + +
      +
    1. Change directory into the object root directory: +
      + cd OBJ_ROOT +

      -

      gmake ENABLE_PROFILING=1 -
      - Perform a Profiling build. -

      +

    2. Run the configure script located in the LLVM source tree: +
      + SRC_ROOT/configure --prefix=/install/path [other options] +

      +

    -
    gmake VERBOSE=1 -
    - Print what gmake is doing on standard output. -

    - +

    In addition to running configure, you must set the +LLVM_LIB_SEARCH_PATH environment variable in your startup shell +scripts. This environment variable is used to locate "system" libraries like +"-lc" and "-lm" when linking. This variable should be set to +the absolute path of the bytecode-libs subdirectory of the GCC front +end, or LLVMGCCDIR/bytecode-libs. For example, one might set +LLVM_LIB_SEARCH_PATH to +/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs for the x86 +version of the GCC front end on our research machines.

    - Every directory in the LLVM source tree includes a Makefile to - build it and any subdirectories that it contains. Entering any directory - inside the LLVM source tree and typing gmake should rebuild - anything in or below that directory that is out of date. +
    - -

    The Location of LLVM Object Files

    - + +
    + Compiling the LLVM Suite Source Code +
    -

    The LLVM build system sends most output files generated during the build - into the directory defined by the variable OBJ_ROOT in - llvm/Makefile.config, which is set by the --with-objroot - option in configure. 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. +

    -

    - If OBJ_ROOT 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 (unless OBJ_ROOT is set to - ., in which case object files are placed within the LLVM source - tree). -

    +

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

    +
    +
    Debug Builds +
    + These builds are the default when one types gmake (unless the + --enable-optimized option was used during configuration). The + build system will compile the tools and libraries with debugging + information.

    - Note that - --with-objroot=. - and - --with-objroot=`pwd` - are not the same thing. The former will simply place object files within - the source tree, while the latter will set the location of object files - using the source tree's relative path from the home directory. -

    +
    Release (Optimized) Builds +
    + These builds are enabled with the --enable-optimized option to + configure or by specifying ENABLE_OPTIMIZED=1 on the + gmake command line. For these builds, the build system will + compile the tools and libraries with GCC optimizations enabled and strip + debugging information from the libraries and executables it generates.

    - For example, suppose that OBJ_ROOT is set to /tmp and the - LLVM suite source code is located in /usr/home/joe/src/llvm, where - /usr/home/joe is the home directory of a user named Joe. Then, - the object files will be placed in /tmp/src/llvm. -

    -

    - The LLVM build will place files underneath OBJ_ROOT in directories - named after the build type: -

    - -
    -
    Debug Builds -
    -
    -
    Tools -
    OBJ_ROOT/llvm/tools/Debug -
    Libraries -
    OBJ_ROOT/llvm/lib/Debug -
    -

    - -

    Release Builds -
    -
    -
    Tools -
    OBJ_ROOT/llvm/tools/Release -
    Libraries -
    OBJ_ROOT/llvm/lib/Release -
    -

    - -

    Profile Builds -
    -
    -
    Tools -
    OBJ_ROOT/llvm/tools/Profile -
    Libraries -
    OBJ_ROOT/llvm/lib/Profile -
    +
    Profile Builds +
    + These builds are for use with profiling. They compile profiling + information into the code for use with programs like gprof. + Profile builds must be started by specifying ENABLE_PROFILING=1 + on the gmake command line. +
    + +

    Once you have LLVM configured, you can build it by entering the +OBJ_ROOT directory and issuing the following command:

    + +

    gmake

    + +

    If the build fails, please check here to see if you +are using a version of GCC that is known not to compile LLVM.

    + +

    +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:

    + +

    gmake -j2

    + +

    There are several special targets which are useful when working with the LLVM +source code:

    + +
    +
    gmake clean +
    + Removes all files generated by the build. This includes object files, + generated C/C++ files, libraries, and executables. +

    + +

    gmake dist-clean +
    + Removes everything that gmake clean does, but also removes files + generated by configure. It attempts to return the source tree to the + original state in which it was shipped. +

    + +

    gmake install +
    + Installs LLVM header files, libraries, tools, and documentation in a + hierarchy + under $PREFIX, specified with ./configure --prefix=[dir], which + defaults to /usr/local. +

    + +

    gmake -C runtime install-bytecode +
    + Assuming you built LLVM into $OBJDIR, when this command is run, it will + install bytecode libraries into the GCC front end's bytecode library + directory. If you need to update your bytecode libraries, + this is the target to use once you've built them. +

    +

    + +

    Please see the Makefile Guide for further +details on these make targets and descriptions of other targets +available.

    + +

    It is also possible to override default values from configure by +declaring variables on the command line. The following are some examples:

    + +
    +
    gmake ENABLE_OPTIMIZED=1 +
    + Perform a Release (Optimized) build. +

    + +

    gmake ENABLE_PROFILING=1 +
    + Perform a Profiling build. +

    + +

    gmake VERBOSE=1 +
    + Print what gmake is doing on standard output. +

    + +

    gmake TOOL_VERBOSE=1
    +
    Ask each tool invoked by the makefiles to print out what it is doing on + the standard output. This also implies VERBOSE=1. +

    +
    + +

    Every directory in the LLVM object tree includes a Makefile to build +it and any subdirectories that it contains. Entering any directory inside the +LLVM object tree and typing gmake should rebuild anything in or below +that directory that is out of date.

    + +
    + + +
    + The Location of LLVM Object Files +
    + +
    + +

    The LLVM build system is capable of sharing a single LLVM source tree among +several LLVM builds. Hence, it is possible to build LLVM for several different +platforms or configurations using the same source tree.

    + +

    This is accomplished in the typical autoconf manner:

    + + + +

    The LLVM build will place files underneath OBJ_ROOT in directories +named after the build type:

    + +
    +
    Debug Builds +
    +
    +
    Tools +
    OBJ_ROOT/Debug/bin +
    Libraries +
    OBJ_ROOT/Debug/lib +
    +

    + +

    Release Builds +
    +
    +
    Tools +
    OBJ_ROOT/Release/bin +
    Libraries +
    OBJ_ROOT/Release/lib +
    +

    + +

    Profile Builds +
    +
    +
    Tools +
    OBJ_ROOT/Profile/bin +
    Libraries +
    OBJ_ROOT/Profile/lib +
    +
    + +
    + + +
    + Optional Configuration Items +
    + +
    + +

    +If you're running on a linux system that supports the " + binfmt_misc" +module, and you have root access on the system, you can set your system up to +execute LLVM bytecode files directly. To do this, use commands like this (the +first command may not be required if you are already using the module):

    + +
    +   $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
+   $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
+   $ chmod u+x hello.bc                (if needed)
+   $ ./hello.bc
+
    + +

    +This allows you to execute LLVM bytecode files directly. Thanks to Jack +Cummings for pointing this out! +

    + +
    + + + +
    + Program Layout +
    + + +
    + +

    One useful source of information about the LLVM source base is the LLVM doxygen documentation available at http://llvm.cs.uiuc.edu/doxygen/. +The following is a brief introduction to code layout:

    + +
    + + +
    CVS directories
    +
    +

    Every directory checked out of CVS will contain a CVS directory; for +the most part these can just be ignored.

    +
    + + +
    llvm/examples
    +
    +

    This directory contains some simple examples of how to use the LLVM IR and + JIT.

    +
    + + +
    llvm/include
    +
    + +

    This directory contains public header files exported from the LLVM +library. The three main subdirectories of this directory are:

    + +
    +
    llvm/include/llvm
    +
    This directory contains all of the LLVM specific header files. This + directory also has subdirectories for different portions of LLVM: + Analysis, CodeGen, Target, Transforms, + etc...
    + +
    llvm/include/llvm/Support
    +
    This directory contains generic support libraries that are provided with + LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities + and a Command Line option processing library store their header files here. +
    + +
    llvm/include/llvm/Config
    +
    This directory contains header files configured by the configure + 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.
    +
    +
    + + +
    llvm/lib
    +
    + +

    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 tools.

    + +
    +
    llvm/lib/VMCore/
    +
    This directory holds the core LLVM source files that implement core + classes like Instruction and BasicBlock.
    + +
    llvm/lib/AsmParser/
    +
    This directory holds the source code for the LLVM assembly language parser + library.
    + +
    llvm/lib/ByteCode/
    +
    This directory holds code for reading and write LLVM bytecode.
    + +
    llvm/lib/Analysis/
    This directory contains a variety of + different program analyses, such as Dominator Information, Call Graphs, + Induction Variables, Interval Identification, Natural Loop Identification, + etc.
    + +
    llvm/lib/Transforms/
    +
    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 Invariant Code Motion, Dead Global + Elimination, and many others.
    + +
    llvm/lib/Target/
    +
    This directory contains files that describe various target architectures + for code generation. For example, the llvm/lib/Target/SparcV9 + directory holds the Sparc machine description while + llvm/lib/Target/CBackend implements the LLVM-to-C converter
    + +
    llvm/lib/CodeGen/
    +
    This directory contains the major parts of the code generator: Instruction + Selector, Instruction Scheduling, and Register Allocation.
    + +
    llvm/lib/Debugger/
    +
    This directory contains the source level debugger library that makes + it possible to instrument LLVM programs so that a debugger could identify + source code locations at which the program is executing.
    + +
    llvm/lib/ExecutionEngine/
    +
    This directory contains libraries for executing LLVM bytecode directly + at runtime in both interpreted and JIT compiled fashions.
    + +
    llvm/lib/Support/
    +
    This directory contains the source code that corresponds to the header + files located in llvm/include/Support/.
    + +
    llvm/lib/System/
    +
    This directory contains the operating system abstraction layer that + shields LLVM from platform-specific coding.
    +
    + +
    + + +
    llvm/projects
    +
    +

    This directory contains projects that are not strictly part of LLVM but are + shipped with LLVM. This is also the directory where you should create your own + LLVM-based projects. See llvm/projects/sample for an example of how + to set up your own project. See llvm/projects/Stacker for a fully + functional example of a compiler front end.

    +
    + + +
    llvm/runtime
    +
    + +

    This directory contains libraries which are compiled into LLVM bytecode and +used when linking programs with the GCC front end. Most of these libraries are +skeleton versions of real libraries; for example, libc is a stripped down +version of glibc.

    + +

    Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front +end to compile.

    + +
    + + +
    llvm/test
    +
    +

    This directory contains feature and regression tests and other basic sanity + checks on the LLVM infrastructure. These are intended to run quickly and cover + a lot of territory without being exhaustive.

    +
    + + +
    llvm-test
    +
    +

    This is not a directory in the normal llvm module; it is a separate CVS + module that must be checked out (usually to projects/llvm-test). This + module contains a comprehensive correctness, performance, and benchmarking + test + suite for LLVM. It is a separate CVS module because not every LLVM user is + interested in downloading or building such a comprehensive test. For further + details on this test suite, please see the + Testing Guide document.

    +
    + + +
    llvm/tools
    +
    + +

    The tools 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 tool_name --help. The +following is a brief introduction to the most important tools. More detailed +information is in the Command Guide.

    + +
    +
    analyze
    +
    analyze 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.
    + +
    bugpoint
    +
    bugpoint is used to debug + optimization passes or code generation backends by narrowing down the + given test case to the minimum number of passes and/or instructions that + still cause a problem, whether it is a crash or miscompilation. See HowToSubmitABug.html for more information + on using bugpoint.
    + +
    llvmc
    +
    The LLVM Compiler Driver. This program can + be configured to utilize both LLVM and non-LLVM compilation tools to enable + pre-processing, translation, optimization, assembly, and linking of programs + all from one command line. llvmc also takes care of processing the + dependent libraries found in bytecode. This reduces the need to get the + traditional -l<name> options right on the command line. Please + note that this tool is new in 1.4 and considered experimental. It will be + fully supported in 1.5.
    + +
    llvm-ar
    +
    The archiver produces an archive containing + the given LLVM bytecode files, optionally with an index for faster + lookup.
    + +
    llvm-as
    +
    The assembler transforms the human readable LLVM assembly to LLVM + bytecode.
    + +
    llvm-dis
    +
    The disassembler transforms the LLVM bytecode to human readable + LLVM assembly.
    + +
    llvm-ld
    +
    llvm-ld is very similar to gccld and provides a general purpose + and extensible linker for LLVM. This is the linker invoked by llvmc. + It allows optimization modules to be loaded so that language specific + optimizations can be applied at link time. Please note that this tool is new + in LLVM 1.4 and still considered experimental. It will be fully supported in + LLVM 1.5.
    + +
    llvm-link
    +
    llvm-link, not surprisingly, links multiple LLVM modules into + a single program.
    + +
    lli
    +
    lli is the LLVM interpreter, which + can directly execute LLVM bytecode (although very slowly...). In addition + to a simple interpreter, lli also has a tracing mode (entered by + specifying -trace on the command line). Finally, for + architectures that support it (currently x86, Sparc, and PowerPC), by default, + lli will function as a Just-In-Time compiler (if the + functionality was compiled in), and will execute the code much + faster than the interpreter.
    + +
    llc
    +
    llc is the LLVM backend compiler, which + translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with + the -march=c option).
    + +
    llvmgcc
    +
    llvmgcc 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 -c, -S, -E, + -o options that are typically used. The source code for the + llvmgcc tool is currently not included in the LLVM CVS tree + because it is quite large and not very interesting. +
    +
    +
    gccas
    +
    This tool is invoked by the llvmgcc 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 + llvmgcc -c x.c -o x.o, you are causing gccas to be + run, which writes the x.o file (which is an LLVM bytecode file + that can be disassembled or manipulated just like any other bytecode + file). The command line interface to gccas is designed to be + as close as possible to the system `as' utility so that + the gcc frontend itself did not have to be modified to interface to + a "weird" assembler.
    + +
    gccld
    +
    gccld 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 gccas, the command line interface of gccld is + designed to match the system linker, to aid interfacing with the GCC + frontend.
    +
    +
    + +
    opt
    +
    opt 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 'opt --help' + command is a good way to get a list of the program transformations + available in LLVM.
    +
    +
    + + +
    llvm/utils
    +
    + +

    This directory contains utilities for working with LLVM source code, and some +of the utilities are actually required as part of the build process because they +are code generators for parts of LLVM infrastructure.

    + +
    +
    Burg/
    Burg is an instruction selector + generator -- it builds trees on which it then performs pattern-matching to + select instructions according to the patterns the user has specified. Burg + is currently used in the Sparc V9 backend.

    + +

    codegen-diff
    codegen-diff is a script + that finds differences between code that LLC generates and code that LLI + generates. This is a useful tool if you are debugging one of them, + assuming that the other generates correct output. For the full user + manual, run `perldoc codegen-diff'.

    + +

    cvsupdate
    cvsupdate is a script that will + update your CVS tree, but produce a much cleaner and more organized output + than simply running `cvs -z3 up -dP' will. For example, it will group + together all the new and updated files and modified files in separate + sections, so you can see at a glance what has changed. If you are at the + top of your LLVM CVS tree, running utils/cvsupdate is the + preferred way of updating the tree.

    + +

    emacs/
    The emacs directory contains + syntax-highlighting files which will work with Emacs and XEmacs editors, + providing syntax highlighting support for LLVM assembly files and TableGen + description files. For information on how to use the syntax files, consult + the README file in that directory.

    + +

    getsrcs.sh
    The getsrcs.sh script finds + and outputs all non-generated source files, which is useful if one wishes + to do a lot of development across directories and does not want to + individually find each file. One way to use it is to run, for example: + xemacs `utils/getsources.sh` from the top of your LLVM source + tree.

    + +

    llvmgrep
    +
    This little tool performs an "egrep -H -n" on each source file in LLVM and + passes to it a regular expression provided on llvmgrep's command + line. This is a very efficient way of searching the source base for a + particular regular expression.
    + +
    makellvm
    The makellvm script compiles all + files in the current directory and then compiles and links the tool that + is the first argument. For example, assuming you are in the directory + llvm/lib/Target/Sparc, if makellvm is in your path, + simply running makellvm llc will make a build of the current + directory, switch to directory llvm/tools/llc and build it, + causing a re-linking of LLC.

    + +

    NightlyTest.pl and + NightlyTestTemplate.html
    These files are used in a + cron script to generate nightly status reports of the functionality of + tools, and the results can be seen by following the appropriate link on + the LLVM homepage.

    + +

    TableGen/
    The TableGen directory contains + the tool used to generate register descriptions, instruction set + descriptions, and even assemblers from common TableGen description + files.

    + +

    vim/
    The vim directory contains + syntax-highlighting files which will work with the VIM editor, providing + syntax highlighting support for LLVM assembly files and TableGen + description files. For information on how to use the syntax files, consult + the README file in that directory.

    + +

    + +
    + + +
    llvm/win32
    +
    +

    This directory contains build scripts and project files for use with + Visual C++. This allows developers on Windows to build LLVM without the need + for Cygwin. The contents of this directory should be considered experimental + at this time. +

    +
    + +
    + An Example Using the LLVM Tool Chain +
    + + +
    + +
      +
    1. First, create a simple C file, name it 'hello.c': + 
      +   #include <stdio.h>
+   int main() {
+     printf("hello world\n");
+     return 0;
+   }
+
      2. - -
      -

      Program Layout

      -
      - +

    2. Next, compile the C file into a LLVM bytecode file:

      +

      % llvmgcc hello.c -o hello

      -

      One useful source of information about the LLVM source base is the LLVM doxygen documentation, available at http://llvm.cs.uiuc.edu/doxygen/. The - following is a brief introduction to code layout:

      +

      Note that you should have already built the tools and they have to be + in your path, at least gccas and gccld.

      +

      This will create two result files: hello and + hello.bc. The hello.bc is the LLVM bytecode that + corresponds the the compiled program and the library facilities that it + required. hello is a simple shell script that runs the bytecode + file with lli, making the result directly executable. Note that + all LLVM optimizations are enabled by default, so there is no need for a + "-O3" switch.

      3. - -

      CVS directories

      - +

    3. Run the program. To make sure the program ran, execute one of the + following commands:

      + +

      % ./hello

      + +

      or

      - Every directory checked out of CVS will contain a CVS directory; - for the most part these can just be ignored. +

      % lli hello.bc

      4. +

    4. Use the llvm-dis utility to take a look at the LLVM assembly + code:

      - -

      llvm/include

      - +

      % llvm-dis < hello.bc | less

      5. - This directory contains public header files exported from the LLVM - library. The three main subdirectories of this directory are:

      +

    5. Compile the program to native assembly using the LLC code + generator:

      -
        -
      1. llvm/include/llvm - This directory contains all of the LLVM - specific header files. This directory also has subdirectories for - different portions of LLVM: Analysis, CodeGen, - Reoptimizer, Target, Transforms, etc... - -
      2. llvm/include/Support - 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. - -
      3. llvm/include/Config - This directory contains header files - configured by the configure 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. -
      - - -

      llvm/lib

      - - - 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 tools.

      - -

      -
      llvm/lib/VMCore/
      This directory holds the core LLVM - source files that implement core classes like Instruction and BasicBlock. - -
      llvm/lib/AsmParser/
      This directory holds the source code - for the LLVM assembly language parser library. - -
      llvm/lib/ByteCode/
      This directory holds code for reading - and write LLVM bytecode. - -
      llvm/lib/CWriter/
      This directory implements the LLVM to C - converter. - -
      llvm/lib/Analysis/
      This directory contains a variety of - different program analyses, such as Dominator Information, Call Graphs, - Induction Variables, Interval Identification, Natural Loop Identification, - etc... - -
      llvm/lib/Transforms/
      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, and many others... - -
      llvm/lib/Target/
      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.
      - -
      llvm/lib/CodeGen/
      This directory contains the major parts - of the code generator: Instruction Selector, Instruction Scheduling, and - Register Allocation. - -
      llvm/lib/Reoptimizer/
      This directory holds code related - to the runtime reoptimizer framework that is currently under development. - -
      llvm/lib/Support/
      This directory contains the source code - that corresponds to the header files located in - llvm/include/Support/. -
      +

      % llc hello.bc -o hello.s

      - -

      llvm/test

      - - -

      This directory contains regression tests and source code that is used to - test the LLVM infrastructure...

      - - -

      llvm/tools

      - - -

      The tools 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 tool_name --help. The - following is a brief introduction to the most important tools.

      - -
      -
      as
      The assembler transforms the human readable - LLVM assembly to LLVM bytecode.

      - -

      dis
      The disassembler transforms the LLVM bytecode - to human readable LLVM assembly. Additionally it can convert LLVM - bytecode to C, which is enabled with the -c option.

      - -

      lli
      lli is the LLVM interpreter, which - can directly execute LLVM bytecode (although very slowly...). In addition - to a simple interpreter, lli is also has debugger and tracing - modes (entered by specifying -debug or -trace on the - command line, respectively). Finally, for architectures that support it - (currently only x86 and Sparc), by default, lli will function as - a Just-In-Time compiler (if the functionality was compiled in), and will - execute the code much faster than the interpreter.

      - -

      llc
      llc is the LLVM backend compiler, - which translates LLVM bytecode to a SPARC or x86 assembly file.

      - -

      llvmgcc
      llvmgcc 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 -c, -S, -E, - -o options that are typically used. The source code for the - llvmgcc tool is currently not included in the LLVM cvs tree - because it is quite large and not very interesting.

      - -

        -
        gccas
        This tool is invoked by the - llvmgcc 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 llvmgcc -c x.c -o - x.o, you are causing gccas to be run, which writes the - x.o file (which is an LLVM bytecode file that can be - disassembled or manipulated just like any other bytecode file). The - command line interface to gccas is designed to be as close as - possible to the system 'as' utility so that the gcc - frontend itself did not have to be modified to interface to a "weird" - assembler.

        - -

        gccld
        gccld 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 gccas the command line interface of - gccld is designed to match the system linker, to aid - interfacing with the GCC frontend.

        -

      - -
      opt
      opt 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 'opt --help' - command is a good way to get a list of the program transformations - available in LLVM.

      +

    6. Assemble the native assembly language file into a program:

      - -
      analyze
      analyze 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.

      +

      Solaris:% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native

      +

      Others:% gcc hello.s -o hello.native

      -
      7. +

    7. Execute the native code program:

      - -

      llvm/utils

      - - - This directory contains utilities for working with LLVM sourcecode, and some - of the utilities are actually required as part of the build process because - they are code generators for parts of LLVM infrastructure. - -
      - Burg
      Burg is an instruction selector - generator -- it builds trees on which it then performs pattern-matching to - select instructions according to the patterns the user has specified. Burg - is currently used in the Sparc V9 backend.

      - -

      codegen-diff
      codegen-diff is a script - that finds differences between code that LLC generates and code that LLI - generates. This is a useful tool if you are debugging one of them, - assuming that the other generates correct output. For the full user - manual, run `perldoc codegen-diff'.

      - -

      cvsupdate
      cvsupdate is a script that will - update your CVS tree, but produce a much cleaner and more organized output - than simply running `cvs up -dP' will. For example, it will group - together all the new and updated files and modified files in separate - sections, so you can see at a glance what has changed. If you are at the - top of your LLVM CVS tree, running utils/cvsupdate is the - preferred way of updating the tree.

      - -

      emacs
      The emacs directory contains - syntax-highlighting files which will work with Emacs and XEmacs editors, - providing syntax highlighting support for LLVM assembly files and TableGen - description files.

      - -

      getsrcs.sh
      The getsrcs.sh script finds - and outputs all non-generated source files, which is useful if one wishes - to do a lot of development across directories and does not want to - individually find each file. One way to use it is to run, for example: - xemacs `utils/getsources.sh` from the top of your LLVM source - tree.

      - -

      makellvm
      The makellvm script compiles all - files in the current directory and then compiles and links the tool that - is the first argument. For example, assuming you are in the directory - llvm/lib/Target/Sparc, if makellvm is in your path, - simply running makellvm llc will make a build of the current - directory, switch to directory llvm/tools/llc and build it, - causing a re-linking of LLC.

      - -

      NightlyTest.pl and - NightlyTestTemplate.html
      These files are used in a - cron script to generate nightly status reports of the functionality of - tools, and the results can be seen by following the appropriate link on - the LLVM homepage.

      - -

      TableGen
      The TableGen directory contains - the tool used to generate register descriptions, instruction set - descriptions, and even assemblers from common TableGen description - files.

      - -

      vim
      The vim directory contains - syntax-highlighting files which will work with the VIM editor, providing - syntax highlighting support for LLVM assembly files and TableGen - description files.

      - -

      - - -

      Compiling the LLVM C Front End

      - - -

      - - This step is optional if you have the C front end binary distribution for - your platform. - -

      - - 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. -

      - 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: - -

        -
      1. Ensure that OBJ_ROOT/llvm/tools/Debug is at the - end of your PATH environment variable. The front end - build needs to know where to find the LLVM tools, but you want to - ensure that these tools are not found before the system assembler and - linker that you normally use for compilation. +

        % ./hello.native

        2. -
      2. cd GCCOBJ +
      -
    8. Configure the source code: -
        -
      • On Linux/x86, use -
          -
        • GCCSRC/configure --prefix=LLVMGCCDIR - --enable-languages=c -
        +
    -
  • On Solaris/Sparc, use - - + +
    + Common Problems +
    + -
  • gmake +
    -
  • The build will eventually fail. Don't worry; chances are good that - everything that needed to build is built. +

    If you are having problems building or using LLVM, or if you have any other +general questions about LLVM, please consult the Frequently +Asked Questions page.

    -
  • gmake -k install - + -

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

    - - -

    -
    An Example Using the LLVM Tool Chain
    -

    - + +
    + Links +
    + -
      -
    1. First, create a simple C file, name it 'hello.c': - 
      -   #include <stdio.h>
-   int main() {
-     printf("hello world\n");
-     return 0;
-   }
-
      +
      -
    2. Next, compile the C file into a LLVM bytecode file:

      +

      This document is just an introduction 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:

      - % llvmgcc hello.c -o hello

      +

      - This will create two result files: hello and - hello.bc. The hello.bc is the LLVM bytecode that - corresponds the the compiled program and the library facilities that it - required. hello is a simple shell script that runs the bytecode - file with lli, making the result directly executable.

      + -

    3. Run the program. To make sure the program ran, execute one of the - following commands:

      - - % ./hello

      - - or

      - - % lli hello.bc

      - -

    4. Use the dis utility to take a look at the LLVM assembly - code:

      - - % dis < hello.bc | less

      - -

    5. Compile the program to native Sparc assembly using the code - generator (assuming you are currently on a Sparc system):

      - - % llc hello.bc -o hello.s

      - -

    6. Assemble the native sparc assemble file into a program:

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

      - -

    7. Execute the native sparc program:

      - - % ./hello.sparc

      - -

    - - - -

    -
    Common Problems
    -

    - - - Below are common problems and their remedies: - -
    -
    When I run configure, it finds the wrong C compiler. -
    - The configure script attempts to locate first gcc and - then cc, unless it finds compiler paths set in CC and - CXX for the C and C++ compiler, respectively. - - If configure finds the wrong compiler, either adjust your - PATH environment variable or set CC and CXX - explicitly. -

    - -

    I compile the code, and I get some error about /localhome. -
    - There are several possible causes for this. The first is that you - didn't set a pathname properly when using configure, and it - defaulted to a pathname that we use on our research machines. -

    - 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. - -

    The configure script finds the right C compiler, but it - uses the LLVM linker from a previous build. What do I do? -
    - The configure script uses the PATH to find - executables, so if it's grabbing the wrong linker/assembler/etc, there - are two ways to fix it: -
      -
    1. Adjust your PATH environment variable so that the - correct program appears first in the PATH. This may work, - but may not be convenient when you want them first in your - path for other work. -

      - -

    2. Run configure with an alternative PATH that - is correct. In a Borne compatible shell, the syntax would be: -

      - PATH= ./configure ... -

      - This is still somewhat inconvenient, but it allows - configure to do its work without having to adjust your - PATH permanently. -

    - -
    I've upgraded to a new version of LLVM, and I get strange build - errors. -
    - Sometimes changes to the LLVM source code alters how the build system - works. Changes in libtool, autoconf, or header file dependencies are - especially prone to this sort of problem. -

    - The best thing to try is to remove the old files and re-build. In most - cases, this takes care of the problem. To do this, just type make - clean and then make in the directory that fails to build. -

    + -

    +
    +
    + Valid CSS! + Valid HTML 4.01! - -

    Links

    - - -

    This document is just an introduction 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:

    - - - -
    - - If you have any questions or run into any snags (or you have any - additions...), please send an email to - Chris Lattner.

    - - - -Last modified: Mon Aug 11 13:52:22 CDT 2003 - - + Chris Lattner
    + Reid Spencer
    + The LLVM Compiler Infrastructure
    + Last modified: $Date$ +
    +