This directory and its subdirectories contain source code for LLVM,
a toolkit for the construction of highly optimized compilers,
optimizers, and runtime environments.
+
+## 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+The LLVM Getting Started documentation may be out of date.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 workflow and configuration to get and build the LLVM source:
+
+1. Checkout LLVM (including related subprojects 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 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
+ subprojects 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
+ pathname 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).
+
+ * Run your build tool of choice!
+
+ * 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 build 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
+ ``make -j NNN`` (NNN is the number of parallel jobs, use e.g. 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.