OpenMP runtime call <call> deduplicated. [OMP170]

This optimization remark indicates that a call to an OpenMP runtime call was replaced with the result of an existing one. This occurs when the compiler knows that the result of a runtime call is immutable. Removing duplicate calls is done by replacing all calls to that function with the result of the first call. This cannot be done automatically by the compiler because the implementations of the OpenMP runtime calls live in a separate library the compiler cannot see.

Example

This optimization will trigger for known OpenMP runtime calls whose return value will not change.

void foo(int N) {
  double *A = malloc(N * omp_get_thread_limit());
  double *B = malloc(N * omp_get_thread_limit());

#pragma omp parallel
  work(&A[omp_get_thread_num() * N]);
#pragma omp parallel
  work(&B[omp_get_thread_num() * N]);
}

$ clang -fopenmp -O2 -Rpass=openmp-opt omp170.c
ompi170.c:2:26: remark: OpenMP runtime call omp_get_thread_limit deduplicated. [OMP170]
double *A = malloc(N * omp_get_thread_limit());
                       ^

Diagnostic Scope

OpenMP optimization remark.