Commit 119d8a51 authored by Hans Wennborg's avatar Hans Wennborg
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Merging r351580: 

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r351580 | kli | 2019-01-18 20:57:37 +0100 (Fri, 18 Jan 2019) | 4 lines

[OPENMP][DOCS] Release notes/OpenMP support updates, NFC.

Differential Revision: https://reviews.llvm.org/D56733

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llvm-svn: 351839
parent e264daec

clang/docs/OpenMPSupport.rst

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OpenMP Support

==================



Clang fully supports OpenMP 4.5. Clang supports offloading to X86_64, AArch64,

PPC64[LE] and has `basic support for Cuda devices`_.



Standalone directives

=====================



* #pragma omp [for] simd: :good:`Complete`.



* #pragma omp declare simd: :partial:`Partial`.  We support parsing/semantic

  analysis + generation of special attributes for X86 target, but still

  missing the LLVM pass for vectorization.



* #pragma omp taskloop [simd]: :good:`Complete`.



* #pragma omp target [enter|exit] data: :good:`Complete`.



* #pragma omp target update: :good:`Complete`.



* #pragma omp target: :good:`Complete`.

Clang supports the following OpenMP 5.0 features



* #pragma omp declare target: :good:`Complete`.

* The `reduction`-based clauses in the `task` and `target`-based directives.



* #pragma omp teams: :good:`Complete`.

* Support relational-op != (not-equal) as one of the canonical forms of random

  access iterator.



* #pragma omp distribute [simd]: :good:`Complete`.

* Support for mapping of the lambdas in target regions.



* #pragma omp distribute parallel for [simd]: :good:`Complete`.

* Parsing/sema analysis for the requires directive.



Combined directives

===================

* Nested declare target directives.



* #pragma omp parallel for simd: :good:`Complete`.

* Make the `this` pointer implicitly mapped as `map(this[:1])`.



* #pragma omp target parallel: :good:`Complete`.

* The `close` *map-type-modifier*.



* #pragma omp target parallel for [simd]: :good:`Complete`.



* #pragma omp target simd: :good:`Complete`.



* #pragma omp target teams: :good:`Complete`.



* #pragma omp teams distribute [simd]: :good:`Complete`.



* #pragma omp target teams distribute [simd]: :good:`Complete`.



* #pragma omp teams distribute parallel for [simd]: :good:`Complete`.



* #pragma omp target teams distribute parallel for [simd]: :good:`Complete`.

Clang fully supports OpenMP 4.5. Clang supports offloading to X86_64, AArch64,

PPC64[LE] and has `basic support for Cuda devices`_.



Clang does not support any constructs/updates from OpenMP 5.0 except

for `reduction`-based clauses in the `task` and `target`-based directives.

* #pragma omp declare simd: :partial:`Partial`.  We support parsing/semantic

  analysis + generation of special attributes for X86 target, but still

  missing the LLVM pass for vectorization.



In addition, the LLVM OpenMP runtime `libomp` supports the OpenMP Tools

Interface (OMPT) on x86, x86_64, AArch64, and PPC64 on Linux, Windows, and macOS.



General improvements

--------------------

- New collapse clause scheme to avoid expensive remainder operations.

  Compute loop index variables after collapsing a loop nest via the

  collapse clause by replacing the expensive remainder operation with

  multiplications and additions.



- The default schedules for the `distribute` and `for` constructs in a

  parallel region and in SPMD mode have changed to ensure coalesced

  accesses. For the `distribute` construct, a static schedule is used

  with a chunk size equal to the number of threads per team (default

  value of threads or as specified by the `thread_limit` clause if

  present). For the `for` construct, the schedule is static with chunk

  size of one.

  

- Simplified SPMD code generation for `distribute parallel for` when

  the new default schedules are applicable.



.. _basic support for Cuda devices:



Cuda devices support

clang/docs/ReleaseNotes.rst

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@@ -233,12 +233,15 @@ ABI Changes in Clang 
OpenMP Support in Clang

----------------------------------



- OpenMP 5.0 features



  - Support relational-op != (not-equal) as one of the canonical forms of random

    access iterator.



  - Added support for mapping of the lambdas in target regions.



- Added parsing/sema analysis for OpenMP 5.0 requires directive.

  - Added parsing/sema analysis for the requires directive.

  - Support nested declare target directives.

  - Make the `this` pointer implicitly mapped as `map(this[:1])`.

  - Added the `close` *map-type-modifier*.



- Various bugfixes and improvements.
@@ -250,6 +253,15 @@ New features supported for Cuda devices: 


- Fixed support for lastprivate/reduction variables in SPMD constructs.



- New collapse clause scheme to avoid expensive remainder operations.



- New default schedule for distribute and parallel constructs.



- Simplified code generation for distribute and parallel in SPMD mode.



- Flag (``-fopenmp_optimistic_collapse``) for user to limit collapsed

  loop counter width when safe to do so.



- General performance improvement.



CUDA Support in Clang