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)..
LLVM/OpenMP Design & Overview¶
A high-level overview of OpenMP in LLVM can be found here.
OpenACC support 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 OpenMP extensions to make the additional functionality also available in OpenMP applications.
LLVM, since version 11 (12 Oct 2020), has an OpenMP-Aware optimization pass as well as the ability to perform “scalar optimizations” across OpenMP region boundaries.
In-depth discussion of the topic can be found here.
LLVM/OpenMP Optimization Remarks¶
LLVM has an elaborate ecosystem around analysis and optimization remarks issues during compilation. The remarks can be enabled from the clang frontend   in various formats   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 OpenMP Optimization Remarks.
OpenMP Command-Line Argument Reference¶
In addition to the Clang command-line argument reference we also recommend the OpenMP command-line argument reference page that offers a detailed overview of options specific to OpenMP. It also contains a list of OpenMP offloading related command-line arguments.
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 Support and FAQ page.
We also encourage everyone interested in OpenMP in LLVM to get involved.