OpenMP®: Support for the OpenMP language

The OpenMP subproject of LLVM is intended to contain all of the components required to build an executing OpenMP program that are outside the compiler itself.

Here you can find :-

Support for the parts of the OpenMP 4.0 language that are not associated with the "target" constructs are contained in the "runtime" directory. Support for offloading computation via the "target" directive is in the separate "offload" directory. That builds a library that provides the interfaces for transferring code and data to an attached computational device. Initial support here is for the Intel® Xeon Phi™ coprocessor, but work is beginning to support other attached computing devices, and the design is intended to be general. The README.txt in the "offload" directory describes how to build the offload library.

All of the code here is dual licensed under the MIT license and the UIUC License (a BSD-like license). The LICENSE.txt file at the top of the OpenMP project contains the license text and associated patent grants.

Features and Goals

Why have the runtime code here?

It makes sense to have the runtime sources in the same place (and with the same license) as the compiler.

Platform Support

The OpenMP runtime is known to work on

Ports to other architectures and operating systems are welcome.

A full OS and archiecture compatibility matrix is in README.txt


The runtime can be built with gcc, icc or clang. However, note that a runtime built with clang cannot be guaranteed to work with OpenMP code compiled by the other compilers, since clang does not support a 128-bit float type, and cannot therefore generate the code used for reductions of that type (which may occur in user code compiled by the other compilers).

The University of Houston has kindly contributed their test suite (in the "testsuite" directory). Integration and use of this for automatic testing is in progress.

Get it and get involved!

First please review our Developer's Policy.

To check out the code, use:

Note that for an in-tree build, you should check out openmp to llvm/projects.

In-tree build:

Out-of-tree build:

Full details of how to build are in the README.txt and Build_With_CMake.txt (inside the runtime/ subdirectory)


Send discussions to the (OpenMP mailing list).

Design Documents

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