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annotate openmp/docs/remarks/OMP170.rst @ 266:00f31e85ec16 default tip
Added tag current for changeset 31d058e83c98
| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
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| date | Sat, 14 Oct 2023 10:13:55 +0900 |
| parents | c4bab56944e8 |
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| rev | line source |
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llvm original Jul 20 16:41:34 2021
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1 .. _omp170: |
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70dce7da266c
llvm original Jul 20 16:41:34 2021
Shinji KONO <kono@ie.u-ryukyu.ac.jp>
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| 223 | 3 OpenMP runtime call <call> deduplicated. [OMP170] |
| 4 ==================================================================== | |
| 5 | |
| 6 This optimization remark indicates that a call to an OpenMP runtime call was | |
| 7 replaced with the result of an existing one. This occurs when the compiler knows | |
| 8 that the result of a runtime call is immutable. Removing duplicate calls is done | |
| 9 by replacing all calls to that function with the result of the first call. This | |
| 10 cannot be done automatically by the compiler because the implementations of the | |
| 11 OpenMP runtime calls live in a separate library the compiler cannot see. | |
| 12 | |
| 13 Example | |
| 14 ------- | |
| 15 | |
| 16 This optimization will trigger for known OpenMP runtime calls whose return value | |
| 17 will not change. | |
| 18 | |
| 19 .. code-block:: c++ | |
| 20 | |
| 21 void foo(int N) { | |
| 22 double *A = malloc(N * omp_get_thread_limit()); | |
| 23 double *B = malloc(N * omp_get_thread_limit()); | |
| 236 | 24 |
| 223 | 25 #pragma omp parallel |
| 26 work(&A[omp_get_thread_num() * N]); | |
| 27 #pragma omp parallel | |
| 28 work(&B[omp_get_thread_num() * N]); | |
| 29 } | |
| 30 | |
| 31 .. code-block:: console | |
| 32 | |
| 236 | 33 $ clang -fopenmp -O2 -Rpass=openmp-opt omp170.c |
| 223 | 34 ompi170.c:2:26: remark: OpenMP runtime call omp_get_thread_limit deduplicated. [OMP170] |
| 35 double *A = malloc(N * omp_get_thread_limit()); | |
| 36 ^ | |
| 37 | |
| 38 Diagnostic Scope | |
| 39 ---------------- | |
| 40 | |
| 41 OpenMP optimization remark. |