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[OpenMP][Docs] Add more content, call coordinates, FAQ entries, links
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‎openmp/docs/SupportAndFAQ.rst‎

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Support And FAQ
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===============
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Support, Getting Involved, and FAQ
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==================================
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Please do not hesitate to reach out to us via openmp-dev@lists.llvm.org or join
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one of our :ref:`regular calls <calls>`. Some common questions are answered in
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the :ref:`faq`.
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.. _calls:
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Calls
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-----
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OpenMP in LLVM Technical Call
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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- Development updates on OpenMP (and OpenACC) in the LLVM Project, including Clang, optimization, and runtime work.
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- Join `OpenMP in LLVM Technical Call <https://bluejeans.com/544112769//webrtc>`__.
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- Time: Weekly call on every Wednesday 7:00 AM Pacific time.
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- Meeting minutes are `here <https://docs.google.com/document/d/1Tz8WFN13n7yJ-SCE0Qjqf9LmjGUw0dWO9Ts1ss4YOdg/edit>`__.
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- Status tracking `page <https://openmp.llvm.org/docs>`__.
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OpenMP in Flang Technical Call
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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- Development updates on OpenMP and OpenACC in the Flang Project.
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- Join `OpenMP in Flang Technical Call <https://bit.ly/39eQW3o>`_
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- Time: Weekly call on every Thursdays 8:00 AM Pacific time.
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- Meeting minutes are `here <https://docs.google.com/document/d/1yA-MeJf6RYY-ZXpdol0t7YoDoqtwAyBhFLr5thu5pFI>`__.
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- Status tracking `page <https://docs.google.com/spreadsheets/d/1FvHPuSkGbl4mQZRAwCIndvQx9dQboffiD-xD0oqxgU0/edit#gid=0>`__.
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.. _faq:
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FAQ
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---
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.. note::
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The FAQ is a work in progress and most of the expected content is not
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yet available. While you can expect changes, we always welcome feedback and
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additions. Please contact, e.g., through ``openmp-dev@lists.llvm.org``.
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Q: How to contribute a patch to the webpage or any other part?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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All patches go through the regular `LLVM review process
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<https://llvm.org/docs/Contributing.html#how-to-submit-a-patch>`_.
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.. _build_offload_capable_compiler:
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Q: How to build an OpenMP offload capable compiler?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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To build an *effective* OpenMP offload capable compiler we recommend a two
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stage build. The first stage Clang does not require to be offload capable but
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all backends that are targeted by OpenMP need to be enabled. By default, Clang
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will be build with all backends enabled. This initial (stage 1) Clang is used
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to create a second Clang compiler that is offload capable as well as the
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:ref:`device runtime libraries <device_runtime>` that will be linked into the
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offloaded code to provide OpenMP runtime support on the device.
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Generic information about building LLVM is available `here
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<https://llvm.org/docs/GettingStarted.html>`__. The CMake options for the
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second stage Clang should include:
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- `LIBOMPTARGET_NVPTX_CUDA_COMPILER=$STAGE1/bin/clang` to use the stage one
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compiler for the device runtime compilation.
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- `LIBOMPTARGET_NVPTX_ENABLE_BCLIB=ON` to enable efficient device runtimes in
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bitcode format.
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If your build machine is not the target machine or automatic detection of the
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available GPUs failed, you should also set:
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- `CLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_XX` where `XX` is the architecture of your GPU, e.g, 80.
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- `LIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=YY` where `YY` is the numeric compute capacity of your GPU, e.g., 75.
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.. note::
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The compiler that generates the offload code should be the same (version) as
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the compiler that build the OpenMP device runtimes. The OpenMP host runtime
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can be build by a different compiler.
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.. _advanced_builds: https://llvm.org//docs/AdvancedBuilds.html
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Q: Does OpenMP offloading support work in pre-packaged LLVM releases?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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For now, the answer is most likely *no*. Please see :ref:`build_offload_capable_compiler`.
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Q: Does OpenMP offloading support work in packages distributed as part of my OS?
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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For now, the answer is most likely *no*. Please see :ref:`build_offload_capable_compiler`.

‎openmp/docs/design/Overview.rst‎

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==================================
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Resources
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---------
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- OpenMP Booth @ SC19: "OpenMP clang and flang Development" https://youtu.be/6yOa-hRi63M
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.. toctree::
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:glob:

‎openmp/docs/design/Runtimes.rst‎

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LLVM/OpenMP Target Host Runtime Plugins (``libomptarget.rtl.XXXX``)
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-------------------------------------------------------------------
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.. _device_runtime:
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LLVM/OpenMP Target Device Runtime (``libomptarget-ARCH-SUBARCH.bc``)
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--------------------------------------------------------------------
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‎openmp/docs/index.rst‎

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remarks/OptimizationRemarks
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Support & Frequently Asked Questions (FAQ)
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==========================================
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Support, Getting Involved, and Frequently Asked Questions (FAQ)
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===============================================================
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Dealing with OpenMP can be complicated. For help with the setup of an OpenMP
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(offload) capable compiler toolchain, its usage, and common problems, consult
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the :doc:`Support and FAQ <SupportAndFAQ>` page.
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We also encourage everyone interested in OpenMP in LLVM to :doc:`get involved
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<SupportAndFAQ>`.
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.. toctree::
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:hidden:

‎openmp/docs/optimizations/OpenMPOpt.rst‎

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OpenMPOpt
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---------
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Resources
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---------
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- 2020 LLVM Developers’ Meeting: "(OpenMP) Parallelism-Aware Optimizations" https://youtu.be/gtxWkeLCxmU
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- 2019 EuroLLVM Developers’ Meeting: "Compiler Optimizations for (OpenMP) Target Offloading to GPUs" https://youtu.be/3AbS82C3X30
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‎openmp/docs/optimizations/OpenMPUnawareOptimizations.rst‎

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OpenMP-Unaware Optimizations
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============================
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Resources
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---------
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- 2018 LLVM Developers’ Meeting: "Optimizing Indirections, using abstractions without remorse" https://youtu.be/zfiHaPaoQPc
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- 2019 LLVM Developers’ Meeting: "The Attributor: A Versatile Inter-procedural Fixpoint Iteration Framework" https://youtu.be/CzWkc_JcfS0

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