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[flang][OpenMP] Improve handling of REQUIRES ATOMIC_DEFAULT_MEM_ORDER (#143917)

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According to OpenMP 5.0 rules, the ACQ_REL ordering coming from a
REQUIRES directive may need to be replaced with ACQUIRE or RELEASE
depending on the directive in the ATOMIC construct. This was not done,
leading to an incorrect "memory-order" clause appearing in the generated
HLFIR.

This may need to be relaxed a bit to fully comply with later spec
versions, that will be done in a future PR.
This commit is contained in:
Krzysztof Parzyszek 2025-06-13 10:29:31 -05:00 committed by GitHub
parent 3ea45a65ed
commit eba63cd76f
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GPG Key ID: B5690EEEBB952194
3 changed files with 40 additions and 5 deletions
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15
flang/lib/Semantics/rewrite-directives.cpp
View File

@ -112,9 +112,22 @@ bool OmpRewriteMutator::Pre(parser::OpenMPAtomicConstruct &x) {
// Add a memory order clause to the atomic directive.
atomicDirectiveDefaultOrderFound_ = true;
llvm::omp::Clause kind{x.GetKind()};
switch (*defaultMemOrder) {
case common::OmpMemoryOrderType::Acq_Rel:
clauseList->v.emplace_back(parser::OmpClause{parser::OmpClause::AcqRel{}});
// FIXME: Implement 5.0 rules, pending clarification on later spec
// versions.
// [5.0:62:22-26]
if (kind == llvm::omp::Clause::OMPC_read) {
clauseList->v.emplace_back(
parser::OmpClause{parser::OmpClause::Acquire{}});
} else if (kind == llvm::omp::Clause::OMPC_update && x.IsCapture()) {
clauseList->v.emplace_back(
parser::OmpClause{parser::OmpClause::AcqRel{}});
} else {
clauseList->v.emplace_back(
parser::OmpClause{parser::OmpClause::Release{}});
}
break;
case common::OmpMemoryOrderType::Relaxed:
clauseList->v.emplace_back(parser::OmpClause{parser::OmpClause::Relaxed{}});

22
flang/test/Lower/OpenMP/requires-atomic-default-mem-order.f90 Normal file
View File

@ -0,0 +1,22 @@
!RUN: %flang_fc1 -emit-hlfir %openmp_flags -fopenmp-version=50 %s -o - | FileCheck %s
module m
!$omp requires atomic_default_mem_order(acq_rel)
contains
!CHECK: %[[V:[0-9]+]]:2 = hlfir.declare {{.*}} {uniq_name = "_QMmFf00Ev"}
!CHECK: %[[X:[0-9]+]]:2 = hlfir.declare {{.*}} {uniq_name = "_QMmFf00Ex"}
!CHECK: omp.atomic.read %[[V]]#0 = %[[X]]#0 memory_order(acquire)
!CHECK: omp.atomic.write %[[X]]#0 = %{{[0-9]+}} memory_order(release)
subroutine f00(x, v)
integer :: x, v
!$omp atomic read
v = x
!$omp atomic write
x = v
end
end module

8
flang/test/Semantics/OpenMP/requires-atomic02.f90
View File

@ -12,7 +12,7 @@ program requires
! CHECK-LABEL: OpenMPAtomicConstruct
! CHECK: OmpClause -> Read
! CHECK: OmpClause -> AcqRel
! CHECK: OmpClause -> Acquire
!$omp atomic read
i = j
@ -36,7 +36,7 @@ program requires
! CHECK-LABEL: OpenMPAtomicConstruct
! CHECK: OmpClause -> Write
! CHECK: OmpClause -> AcqRel
! CHECK: OmpClause -> Release
!$omp atomic write
i = j
@ -60,7 +60,7 @@ program requires
! CHECK-LABEL: OpenMPAtomicConstruct
! CHECK: OmpClause -> Update
! CHECK: OmpClause -> AcqRel
! CHECK: OmpClause -> Release
!$omp atomic update
i = i + j
@ -79,7 +79,7 @@ program requires
i = i + j
! CHECK-LABEL: OpenMPAtomicConstruct
! CHECK: OmpClause -> AcqRel
! CHECK: OmpClause -> Release
!$omp atomic
i = i + j