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.. _omp150:
Parallel region merged with parallel region at <location>. [OMP150]
===================================================================
This optimization remark indicates that a parallel region was merged with others
into a single parallel region. Parallel region merging fuses consecutive
parallel regions to reduce the team activation overhead of forking and increases
the scope of possible OpenMP-specific optimizations within merged parallel
regions. This optimization can also guard sequential code between two parallel
regions if applicable.
Example
-------
This optimization should apply to any compatible and consecutive parallel
regions. In this case the sequential region between the parallel regions will be
guarded so it is only executed by a single thread in the new merged region.
.. code-block:: c++
void foo() {
#pragma omp parallel
parallel_work();
sequential_work();
#pragma omp parallel
parallel_work();
}
.. code-block:: console
$ clang++ -fopenmp -O2 -Rpass=openmp-opt -mllvm -openmp-opt-enable-merging omp150.cpp
omp150.cpp:2:1: remark: Parallel region merged with parallel region at merge.cpp:7:1. [OMP150]
#pragma omp parallel
^
Diagnostic Scope
----------------
OpenMP optimization remark.
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