110 lines
4.3 KiB
Markdown
110 lines
4.3 KiB
Markdown
# The LLVM Compiler Infrastructure
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This directory and its subdirectories contain source code for LLVM,
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a toolkit for the construction of highly optimized compilers,
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optimizers, and runtime environments.
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The README briefly describes how to get started with building LLVM.
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For more information on how to contribute to the LLVM project, please
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take a look at the
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[Contributing to LLVM](https://llvm.org/docs/Contributing.html) guide.
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## Getting Started with the LLVM System
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Taken from https://llvm.org/docs/GettingStarted.html.
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### Overview
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Welcome to the LLVM project!
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The LLVM project has multiple components. The core of the project is
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itself called "LLVM". This contains all of the tools, libraries, and header
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files needed to process intermediate representations and converts it into
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object files. Tools include an assembler, disassembler, bitcode analyzer, and
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bitcode optimizer. It also contains basic regression tests.
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C-like languages use the [Clang](http://clang.llvm.org/) front end. This
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component compiles C, C++, Objective C, and Objective C++ code into LLVM bitcode
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-- and from there into object files, using LLVM.
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Other components include:
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the [libc++ C++ standard library](https://libcxx.llvm.org),
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the [LLD linker](https://lld.llvm.org), and more.
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### Getting the Source Code and Building LLVM
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The LLVM Getting Started documentation may be out of date. The [Clang
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Getting Started](http://clang.llvm.org/get_started.html) page might have more
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accurate information.
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This is an example workflow and configuration to get and build the LLVM source:
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1. Checkout LLVM (including related subprojects like Clang):
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* ``git clone https://github.com/llvm/llvm-project.git``
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* Or, on windows, ``git clone --config core.autocrlf=false
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https://github.com/llvm/llvm-project.git``
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2. Configure and build LLVM and Clang:
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* ``cd llvm-project``
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* ``mkdir build``
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* ``cd build``
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* ``cmake -G <generator> [options] ../llvm``
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Some common generators are:
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* ``Ninja`` --- for generating [Ninja](https://ninja-build.org)
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build files. Most llvm developers use Ninja.
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* ``Unix Makefiles`` --- for generating make-compatible parallel makefiles.
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* ``Visual Studio`` --- for generating Visual Studio projects and
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solutions.
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* ``Xcode`` --- for generating Xcode projects.
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Some Common options:
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* ``-DLLVM_ENABLE_PROJECTS='...'`` --- semicolon-separated list of the LLVM
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subprojects you'd like to additionally build. Can include any of: clang,
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clang-tools-extra, libcxx, libcxxabi, libunwind, lldb, compiler-rt, lld,
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polly, or debuginfo-tests.
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For example, to build LLVM, Clang, libcxx, and libcxxabi, use
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``-DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi"``.
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* ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full
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pathname of where you want the LLVM tools and libraries to be installed
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(default ``/usr/local``).
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* ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug,
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Release, RelWithDebInfo, and MinSizeRel. Default is Debug.
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* ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled
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(default is Yes for Debug builds, No for all other build types).
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* Run your build tool of choice!
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* The default target (i.e. ``ninja`` or ``make``) will build all of LLVM.
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* The ``check-all`` target (i.e. ``ninja check-all``) will run the
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regression tests to ensure everything is in working order.
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* CMake will generate build targets for each tool and library, and most
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LLVM sub-projects generate their own ``check-<project>`` target.
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* Running a serial build will be *slow*. To improve speed, try running a
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parallel build. That's done by default in Ninja; for ``make``, use
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``make -j NNN`` (NNN is the number of parallel jobs, use e.g. number of
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CPUs you have.)
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* For more information see [CMake](https://llvm.org/docs/CMake.html)
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Consult the
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[Getting Started with LLVM](https://llvm.org/docs/GettingStarted.html#getting-started-with-llvm)
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page for detailed information on configuring and compiling LLVM. You can visit
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[Directory Layout](https://llvm.org/docs/GettingStarted.html#directory-layout)
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to learn about the layout of the source code tree.
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