https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113840
Bug ID: 113840
Summary: [OpenACC] !$acc loop seq – bogus rejection of
Fortran's EXIT/CYCLE + C/C++ break/continue
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: openacc, rejects-valid
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: burnus at gcc dot gnu.org
CC: tschwinge at gcc dot gnu.org
Target Milestone: ---
OpenACC seems to permit EXIT and CYCLE in "!$ACC LOOP" if there is the SEQ
clause.
The following quote is from OpenACC 3.2 but it can be also found in 2.5 a bit
less explicit and between the lines also for 1.0 and 2.0:
"2.9 Loop Construct" → "Restrictions"
"A loop associated with a loop construct that does not have a seq clause must
be written to
meet all of the following conditions:1931
– The loop variable must be of integer, C/C++ pointer, or C++ random-access
iterator type.
– The loop variable must monotonically increase or decrease in the direction of
its termination condition.
– The loop trip count must be computable in constant time when entering the
loop construct."
Currently, it fails with:
test.f90:4:6:
4 | EXIT
| 1
Error: EXIT statement at (1) terminating !$ACC LOOP loop
or
test.c:5:7: error: break statement used with OpenMP for loop
5 | break;
| ^~~~~
* * *
Testcases:
----------------------------
!$acc parallel
!$acc loop seq
do i=1, 5
EXIT
end do
!$acc end parallel
end
----------------------------
----------------------------
void f() {
#pragma acc parallel
#pragma acc loop seq
for (int i=1; i < 5; i++)
break;
}
----------------------------
* * *
It seems as if the loop conditions are also relaxed, which needs to be handled
/ supported. (Not folding to OMP_FOR internally – or still? If not: at least
PRIVATE needs to be handled and the SEQ be honored.)
* * *
Real-world testcase:
https://gitlab.dkrz.de/icon/icon-model/-/blob/release-2024.01-public/src/diagnostics/mo_tropopause.f90?ref_type=heads#L200-L213
