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+# The LLVM Compiler Infrastructure
+
+This directory and its sub-directories contain 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, please
+take a look at the
+[Contributing to LLVM](https://llvm.org/docs/Contributing.html) guide.
+
+## Getting Started with the LLVM System
+
+Taken from https://llvm.org/docs/GettingStarted.html.
+
+### Overview
+
+Welcome to the LLVM project!
+
+The LLVM project has multiple components. The core of the project is
+itself called "LLVM". This contains all of the tools, libraries, and header
+files needed to process intermediate representations and converts it into
+object files.  Tools include an assembler, disassembler, bitcode analyzer, and
+bitcode optimizer.  It also contains basic regression tests.
+
+C-like languages use the [Clang](http://clang.llvm.org/) front end.  This
+component compiles C, C++, Objective C, and Objective C++ code into LLVM bitcode
+-- and from there into object files, using LLVM.
+
+Other components include:
+the [libc++ C++ standard library](https://libcxx.llvm.org),
+the [LLD linker](https://lld.llvm.org), and more.
+
+### Getting the Source Code and Building LLVM
+
+The LLVM Getting Started documentation may be out of date.  The [Clang
+Getting Started](http://clang.llvm.org/get_started.html) page might have more
+accurate 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``
+
+     * ``mkdir build``
+
+     * ``cd build``
+
+     * ``cmake -G <generator> [options] ../llvm``
+
+        Some common build system generators are:
+
+        * ``Ninja`` --- for generating [Ninja](https://ninja-build.org)
+          build files. Most llvm developers use Ninja.
+        * ``Unix Makefiles`` --- for generating make-compatible parallel makefiles.
+        * ``Visual Studio`` --- for generating Visual Studio projects and
+          solutions.
+        * ``Xcode`` --- for generating Xcode projects.
+
+        Some Common options:
+
+        * ``-DLLVM_ENABLE_PROJECTS='...'`` --- semicolon-separated list of the LLVM
+          sub-projects you'd like to additionally build. Can include any of: clang,
+          clang-tools-extra, libcxx, libcxxabi, libunwind, lldb, compiler-rt, lld,
+          polly, or debuginfo-tests.
+
+          For example, to build LLVM, Clang, libcxx, and libcxxabi, use
+          ``-DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi"``.
+
+        * ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full
+          path name of where you want the LLVM tools and libraries to be installed
+          (default ``/usr/local``).
+
+        * ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* 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 . [-- [options] <target>]`` or your build system specified above
+        directly.
+
+        * The default target (i.e. ``ninja`` or ``make``) will build all of LLVM.
+
+        * The ``check-all`` target (i.e. ``ninja check-all``) will run the
+          regression tests to ensure everything is in working order.
+
+        * CMake will generate targets for each tool and library, and most
+          LLVM sub-projects generate their own ``check-<project>`` target.
+
+        * Running a serial build will be **slow**.  To improve speed, try running a
+          parallel build.  That's done by default in Ninja; for ``make``, use the option
+          ``-j NNN``, where ``NNN`` is the number of parallel jobs, e.g. the number of
+          CPUs you have.
+
+      * For more information see [CMake](https://llvm.org/docs/CMake.html)
+
+Consult the
+[Getting Started with LLVM](https://llvm.org/docs/GettingStarted.html#getting-started-with-llvm)
+page for detailed information on configuring and compiling LLVM. You can visit
+[Directory Layout](https://llvm.org/docs/GettingStarted.html#directory-layout)
+to learn about the layout of the source code tree.