Repository files navigation

This directory and its sub-directories contain the source code for LLVM,a toolkit for the construction of highly optimized compilers,optimizers, and run-time environments.

The README briefly describes how to get started with building LLVM.For more information on how to contribute to the LLVM project, pleasetake a look at theContributing to LLVM guide.

Taken fromhere.

Welcome to the LLVM project!

The LLVM project has multiple components. The core of the project isitself called "LLVM". This contains all of the tools, libraries, and headerfiles needed to process intermediate representations and convert them intoobject files. Tools include an assembler, disassembler, bitcode analyzer, andbitcode optimizer. It also contains basic regression tests.

C-like languages use theClang frontend. Thiscomponent compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode-- and from there into object files, using LLVM.

Other components include:thelibc++ C++ standard library,theLLD linker, and more.

The LLVM Getting Started documentation may be out of date. TheClangGetting Started page might have moreaccurate information.

This is an example work-flow and configuration to get and build the LLVM source:

1. Checkout LLVM (including related sub-projects like Clang):

   • git clone https://github.com/llvm/llvm-project.git

   • Or, on windows,git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git

2. Configure and build LLVM and Clang:

   • cd llvm-project

   • cmake -S llvm -B build -G <generator> [options]

     Some common build system generators are:

     • Ninja --- for generatingNinjabuild files. Most llvm developers use Ninja.
     • Unix Makefiles --- for generating make-compatible parallel makefiles.
     • Visual Studio --- for generating Visual Studio projects andsolutions.
     • Xcode --- for generating Xcode projects.

     Some common options:

     • -DLLVM_ENABLE_PROJECTS='...' and-DLLVM_ENABLE_RUNTIMES='...' ---semicolon-separated list of the LLVM sub-projects and runtimes you'd like toadditionally build.LLVM_ENABLE_PROJECTS can include any of: clang,clang-tools-extra, cross-project-tests, flang, libc, libclc, lld, lldb,mlir, openmp, polly, or pstl.LLVM_ENABLE_RUNTIMES can include any oflibcxx, libcxxabi, libunwind, compiler-rt, libc or openmp. Some runtimeprojects can be specified either inLLVM_ENABLE_PROJECTS or inLLVM_ENABLE_RUNTIMES.

       For example, to build LLVM, Clang, libcxx, and libcxxabi, use-DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi".

     • -DCMAKE_INSTALL_PREFIX=directory --- Specify fordirectory the fullpath name of where you want the LLVM tools and libraries to be installed(default/usr/local). Be careful if you install runtime libraries: ifyour system uses those provided by LLVM (like libc++ or libc++abi), youmust not overwrite your system's copy of those libraries, since thatcould render your system unusable. In general, using something like/usr is not advised, but/usr/local is fine.

     • -DCMAKE_BUILD_TYPE=type --- Valid options fortype are Debug,Release, RelWithDebInfo, and MinSizeRel. Default is Debug.

     • -DLLVM_ENABLE_ASSERTIONS=On --- Compile with assertion checks enabled(default is Yes for Debug builds, No for all other build types).

   • cmake --build build [-- [options] <target>] or your build system specified abovedirectly.

     • The default target (i.e.ninja ormake) will build all of LLVM.

     • Thecheck-all target (i.e.ninja check-all) will run theregression tests to ensure everything is in working order.

     • CMake will generate targets for each tool and library, and mostLLVM sub-projects generate their owncheck-<project> target.

     • Running a serial build will beslow. To improve speed, try running aparallel build. That's done by default in Ninja; formake, use the option-j NNN, whereNNN is the number of parallel jobs to run.In most cases, you get the best performance if you specify the number of CPU threads you have.On some Unix systems, you can specify this with-j$(nproc).

   • For more information seeCMake.

Consult theGetting Started with LLVMpage for detailed information on configuring and compiling LLVM. You can visitDirectory Layoutto learn about the layout of the source code tree.

JoinLLVM Discourse forums,discord chat or #llvm IRC channel onOFTC.

The LLVM project has adopted acode of conduct forparticipants to all modes of communication within the project.