.. title:: Welcome to the documentation of OpenMP in LLVM!
.. note::
This document is a work in progress and most of the expected content is not
yet available. While you can expect changes, we always welcome feedback and
additions. Please post on the Discourse forums (Runtimes - OpenMP) <https://discourse.llvm.org/c/runtimes/openmp/35>__..
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LLVM/OpenMP Documentation
LLVM/OpenMP Design & Overview
OpenMP impacts various parts of the LLVM project, from the frontends (Clang <https://clang.llvm.org/docs/OpenMPSupport.html>_ and Flang), through
middle-end :ref:optimizations <llvm_openmp_optimizations>, up to the
multitude of available :ref:OpenMP runtimes <openmp_runtimes>.
A high-level overview of OpenMP in LLVM can be found :doc:here <design/Overview>.
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design/Overview
OpenACC Support
:doc:OpenACC support <openacc/Overview> is under development for
both Flang and Clang. For this purpose, LLVM's OpenMP runtimes are
being extended to serve as OpenACC runtimes. In some cases, Clang
supports :doc:OpenMP extensions <openacc/OpenMPExtensions> to make
the additional functionality also available in OpenMP applications.
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openacc/Overview
LLVM/OpenMP Optimizations
LLVM, since version 11 (12 Oct
2020), has an :doc:OpenMP-Aware optimization pass <optimizations/OpenMPOpt>
as well as the ability to :doc:perform "scalar optimizations" across OpenMP region boundaries <optimizations/OpenMPUnawareOptimizations>.
In-depth discussion of the topic can be found :doc:here <optimizations/Overview>.
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optimizations/Overview
LLVM/OpenMP Optimization Remarks
LLVM has an elaborate ecosystem around analysis and optimization remarks <https://llvm.org/docs/Remarks.html>_ issues during
compilation. The remarks can be enabled from the clang frontend [1]_ [2]_
in various formats [3]_ [4]_ to be used by tools, i.a., opt-viewer or
llvm-opt-report (dated).
The OpenMP optimizations in LLVM have been developed with remark support as a
priority. For a list of OpenMP specific remarks and more information on them,
please refer to :doc:remarks/OptimizationRemarks.
.. _[1]: https://clang.llvm.org/docs/UsersManual.html#options-to-emit-optimization-reports
.. _[2]: https://clang.llvm.org/docs/ClangCommandLineReference.html#diagnostic-flags
.. _[3]: https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-foptimization-record-file
.. _[4]: https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang1-fsave-optimization-record
[1]_ https://clang.llvm.org/docs/UsersManual.html#options-to-emit-optimization-reports[2]_ https://clang.llvm.org/docs/ClangCommandLineReference.html#diagnostic-flags[3]_ https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-foptimization-record-file[4]_ https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang1-fsave-optimization-record
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remarks/OptimizationRemarks
OpenMP Command-Line Argument Reference
In addition to the
Clang command-line argument reference
we also recommend the OpenMP
:doc:command-line argument reference <CommandLineArgumentReference>
page that offers a detailed overview of options specific to OpenMP. It also
contains a list of OpenMP offloading related command-line arguments.
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CommandLineArgumentReference
Support, Getting Involved, and Frequently Asked Questions (FAQ)
Dealing with OpenMP can be complicated. For help with the setup of an OpenMP
(offload) capable compiler toolchain, its usage, and common problems, consult
the :doc:Support and FAQ <SupportAndFAQ> page.
We also encourage everyone interested in OpenMP in LLVM to :doc:get involved <SupportAndFAQ>.
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SupportAndFAQ
Release Notes
The current (in-progress) release notes can be found :doc:here <ReleaseNotes> while
release notes for releases, starting with LLVM 12, will be available on the Download Page <https://releases.llvm.org/download.html>_.
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In-Progress ReleaseNotes