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1.. _omp121:2 3Value has potential side effects preventing SPMD-mode execution. Add `[[omp::assume(\"ompx_spmd_amenable\")]]` to the called function to override. [OMP121]4===================================================================================================================================================================5 6This analysis remarks indicates that a potential side-effect that cannot be7guarded prevents the target region from executing in SPMD-mode. SPMD-mode8requires that each thread is active inside the region. Any instruction that9cannot be either recomputed by each thread independently or guarded and executed10by a single thread prevents the region from executing in SPMD-mode.11 12This remark will attempt to print out the instructions preventing the region13from being executed in SPMD-mode. Calls to functions outside the current14translation unit will prevent this transformation from occurring as well, but15can be overridden using an assumption stating that it contains no calls that16prevent SPMD execution.17 18Examples19--------20 21Calls to functions outside the current translation unit may contain instructions22or operations that cannot be executed in SPMD-mode.23 24.. code-block:: c++25 26 extern int work();27 28 void use(int x);29 30 void foo() {31 #pragma omp target teams32 {33 int x = work();34 #pragma omp parallel35 use(x);36 37 }38 }39 40 41.. code-block:: console42 43 $ clang++ -fopenmp -fopenmp-targets=nvptx64 -O2 -Rpass-analysis=openmp-opt omp121.cpp44 omp121.cpp:8:13: remark: Value has potential side effects preventing SPMD-mode45 execution. Add `[[omp::assume("ompx_spmd_amenable")]]` to the called function46 to override. [OMP121]47 int x = work();48 ^49 50As the remark suggests, the problem is caused by the unknown call to the51external function ``work``. This can be overridden by asserting that it does not52contain any code that prevents SPMD-mode execution.53 54.. code-block:: c++55 56 [[omp::assume("ompx_spmd_amenable")]] extern int work();57 58 void use(int x);59 60 void foo() {61 #pragma omp target teams62 {63 int x = work();64 #pragma omp parallel65 use(x);66 67 }68 }69 70.. code-block:: console71 72 $ clang++ -fopenmp -fopenmp-targets=nvptx64 -O2 -Rpass=openmp-opt omp121.cpp73 omp121.cpp:6:1: remark: Transformed generic-mode kernel to SPMD-mode. [OMP120]74 #pragma omp target teams75 ^76 77Diagnostic Scope78----------------79 80OpenMP target offloading analysis remark.81