| Issue |
179250
|
| Summary |
Flang OpenMP: Incorrect diagnostic for closely nested worksharing regions
|
| Labels |
flang
|
| Assignees |
|
| Reporter |
blazie2004
|
### Problem
Flang incorrectly rejects valid OpenMP code containing nested PARALLEL SECTIONS and PARALLEL DO constructs with the error:
```
error: A worksharing region may not be closely nested inside a worksharing,
explicit task, taskloop, critical, ordered, atomic, or master region
```
### Cause
PARALLEL SECTIONS is a combined construct that creates its own parallel region. Flang incorrectly treats it as a simple worksharing construct when checking nesting rules.
Per OpenMP 5.0 Section 2.13.3, PARALLEL SECTIONS is equivalent to:
```
!$OMP PARALLEL
!$OMP SECTIONS
...
!$OMP END SECTIONS
!$OMP END PARALLEL
```
Since it includes a PARALLEL region, it should be allowed to nest inside other parallel regions.
### Testcase
```
program omp_small
implicit none
integer :: i, j
!$omp parallel sections
!$omp section
!$omp parallel sections
!$omp section
i = 1
!$omp end parallel sections
!$omp section
!$omp parallel do
do i = 1, 4
j = i
end do
!$omp end parallel do
!$omp end parallel sections
end program omp_small
```
### Expected Behavior
Code compiles perfectly
### Current Behavior
```
error: A worksharing region may not be closely nested inside a worksharing,
explicit task, taskloop, critical, ordered, atomic, or master region
!$OMP PARALLEL SECTIONS
```
I will provide a fix that addresses this issue by raising a pr , if analysis looks correct .
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