[flang-commits] [flang] [Flang][OpenMP] Fix nested PARALLEL SECTIONS validation (PR #179419)
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flang-commits at lists.llvm.org
Mon Feb 9 07:23:45 PST 2026
https://github.com/blazie2004 updated https://github.com/llvm/llvm-project/pull/179419
>From 81012d8e6f1c763e49ceebc6c103bcc09bcb6b72 Mon Sep 17 00:00:00 2001
From: Jay Satish Kumar Patel <kumarpat at pe31.hpc.amslabs.hpecorp.net>
Date: Tue, 3 Feb 2026 03:22:22 -0600
Subject: [PATCH 1/2] [Flang][OpenMP] Fix nested PARALLEL SECTIONS validation
---
flang/lib/Semantics/check-omp-loop.cpp | 2 +-
flang/lib/Semantics/check-omp-structure.cpp | 30 +++++++++++++++++----
flang/lib/Semantics/check-omp-structure.h | 6 +++--
3 files changed, 30 insertions(+), 8 deletions(-)
diff --git a/flang/lib/Semantics/check-omp-loop.cpp b/flang/lib/Semantics/check-omp-loop.cpp
index 20c52ba3417ad..2ba1432afab02 100644
--- a/flang/lib/Semantics/check-omp-loop.cpp
+++ b/flang/lib/Semantics/check-omp-loop.cpp
@@ -460,7 +460,7 @@ void OmpStructureChecker::Enter(const parser::OpenMPLoopConstruct &x) {
// nesting check
HasInvalidWorksharingNesting(
- beginName.source, llvm::omp::nestedWorkshareErrSet);
+ beginName.source, llvm::omp::nestedWorkshareErrSet,beginName.v);
}
SetLoopInfo(x);
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 6f08ebecc7ddf..082fc64441b5a 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -633,11 +633,31 @@ void OmpStructureChecker::CheckMultListItems() {
CheckMultipleOccurrence(listVars, nameList, clause->source, "LINEAR");
}
}
+bool OmpStructureChecker::IsCombinedParallelWorksharing(
+ llvm::omp::Directive directive) const {
+ // Combined parallel-worksharing constructs create their own parallel region
+ // They should not be subject to worksharing nesting restrictions
+ switch (directive) {
+ case llvm::omp::OMPD_parallel_for:
+ return true;
+ case llvm::omp::OMPD_parallel_for_simd:
+ return true;
+ case llvm::omp::OMPD_parallel_sections:
+ return true;
+ case llvm::omp::OMPD_parallel_workshare:
+ return true;
+ default:
+ return false;
+ }
+}
bool OmpStructureChecker::HasInvalidWorksharingNesting(
- const parser::CharBlock &source, const OmpDirectiveSet &set) {
+ const parser::CharBlock &source, const OmpDirectiveSet &set,llvm::omp::Directive directive) {
// set contains all the invalid closely nested directives
// for the given directive (`source` here)
+ if (IsCombinedParallelWorksharing(directive)) {
+ return false;
+ }
if (IsCloselyNestedRegion(set)) {
context_.Say(source,
"A worksharing region may not be closely nested inside a "
@@ -1056,7 +1076,7 @@ void OmpStructureChecker::Enter(const parser::OmpBlockConstruct &x) {
case llvm::omp::OMPD_parallel_workshare:
CheckWorkshareBlockStmts(block, beginSpec.source);
HasInvalidWorksharingNesting(
- beginSpec.source, llvm::omp::nestedWorkshareErrSet);
+ beginSpec.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
break;
case llvm::omp::OMPD_workdistribute:
if (!CurrentDirectiveIsNested()) {
@@ -1074,7 +1094,7 @@ void OmpStructureChecker::Enter(const parser::OmpBlockConstruct &x) {
// TODO: This check needs to be extended while implementing nesting of
// regions checks.
HasInvalidWorksharingNesting(
- beginSpec.source, llvm::omp::nestedWorkshareErrSet);
+ beginSpec.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
break;
case llvm::omp::Directive::OMPD_task:
for (const auto &clause : beginSpec.Clauses().v) {
@@ -1233,8 +1253,8 @@ void OmpStructureChecker::Enter(const parser::OpenMPSectionsConstruct &x) {
CheckNoBranching(
std::get<parser::Block>(section.t), beginName.v, beginName.source);
}
- HasInvalidWorksharingNesting(
- beginName.source, llvm::omp::nestedWorkshareErrSet);
+ HasInvalidWorksharingNesting(
+ beginName.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
}
void OmpStructureChecker::Leave(const parser::OpenMPSectionsConstruct &) {
diff --git a/flang/lib/Semantics/check-omp-structure.h b/flang/lib/Semantics/check-omp-structure.h
index 9b5b0525dd27f..8afbfd6a6aab2 100644
--- a/flang/lib/Semantics/check-omp-structure.h
+++ b/flang/lib/Semantics/check-omp-structure.h
@@ -192,10 +192,12 @@ class OmpStructureChecker : public OmpStructureCheckerBase {
void CheckMultListItems();
void CheckStructureComponent(
const parser::OmpObjectList &objects, llvm::omp::Clause clauseId);
- bool HasInvalidWorksharingNesting(
- const parser::CharBlock &, const OmpDirectiveSet &);
+ bool HasInvalidWorksharingNesting(
+ const parser::CharBlock &, const OmpDirectiveSet &,
+ llvm::omp::Directive directive);
bool IsCloselyNestedRegion(const OmpDirectiveSet &set);
bool IsNestedInDirective(llvm::omp::Directive directive);
+ bool IsCombinedParallelWorksharing(llvm::omp::Directive directive) const;
bool InTargetRegion();
void HasInvalidTeamsNesting(
const llvm::omp::Directive &dir, const parser::CharBlock &source);
>From 1de8e92872cd59ce6fcf718ce1b9b2a095380d4c Mon Sep 17 00:00:00 2001
From: Jay Satish Kumar Patel <kumarpat at pe31.hpc.amslabs.hpecorp.net>
Date: Mon, 9 Feb 2026 03:18:49 -0600
Subject: [PATCH 2/2] Use OMPD_parallel_do directives and group switch cases
---
flang/lib/Semantics/check-omp-loop.cpp | 2 +-
flang/lib/Semantics/check-omp-structure.cpp | 15 ++---
flang/lib/Semantics/check-omp-structure.h | 5 +-
.../OpenMP/nested_parallel_sections_valid.f90 | 60 +++++++++++++++++++
flang/test/Semantics/OpenMP/workshare04.f90 | 1 -
flang/test/Semantics/OpenMP/workshare05.f90 | 2 +-
6 files changed, 70 insertions(+), 15 deletions(-)
create mode 100644 flang/test/Semantics/OpenMP/nested_parallel_sections_valid.f90
diff --git a/flang/lib/Semantics/check-omp-loop.cpp b/flang/lib/Semantics/check-omp-loop.cpp
index 2ba1432afab02..5f6bbd90929dc 100644
--- a/flang/lib/Semantics/check-omp-loop.cpp
+++ b/flang/lib/Semantics/check-omp-loop.cpp
@@ -460,7 +460,7 @@ void OmpStructureChecker::Enter(const parser::OpenMPLoopConstruct &x) {
// nesting check
HasInvalidWorksharingNesting(
- beginName.source, llvm::omp::nestedWorkshareErrSet,beginName.v);
+ beginName.source, llvm::omp::nestedWorkshareErrSet, beginName.v);
}
SetLoopInfo(x);
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 082fc64441b5a..686498b5635e2 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -638,12 +638,9 @@ bool OmpStructureChecker::IsCombinedParallelWorksharing(
// Combined parallel-worksharing constructs create their own parallel region
// They should not be subject to worksharing nesting restrictions
switch (directive) {
- case llvm::omp::OMPD_parallel_for:
- return true;
- case llvm::omp::OMPD_parallel_for_simd:
- return true;
+ case llvm::omp::OMPD_parallel_do:
+ case llvm::omp::OMPD_parallel_do_simd:
case llvm::omp::OMPD_parallel_sections:
- return true;
case llvm::omp::OMPD_parallel_workshare:
return true;
default:
@@ -656,7 +653,7 @@ bool OmpStructureChecker::HasInvalidWorksharingNesting(
// set contains all the invalid closely nested directives
// for the given directive (`source` here)
if (IsCombinedParallelWorksharing(directive)) {
- return false;
+ return false;
}
if (IsCloselyNestedRegion(set)) {
context_.Say(source,
@@ -1076,7 +1073,7 @@ void OmpStructureChecker::Enter(const parser::OmpBlockConstruct &x) {
case llvm::omp::OMPD_parallel_workshare:
CheckWorkshareBlockStmts(block, beginSpec.source);
HasInvalidWorksharingNesting(
- beginSpec.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
+ beginSpec.source, llvm::omp::nestedWorkshareErrSet, beginSpec.DirId());
break;
case llvm::omp::OMPD_workdistribute:
if (!CurrentDirectiveIsNested()) {
@@ -1094,7 +1091,7 @@ void OmpStructureChecker::Enter(const parser::OmpBlockConstruct &x) {
// TODO: This check needs to be extended while implementing nesting of
// regions checks.
HasInvalidWorksharingNesting(
- beginSpec.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
+ beginSpec.source, llvm::omp::nestedWorkshareErrSet, beginSpec.DirId());
break;
case llvm::omp::Directive::OMPD_task:
for (const auto &clause : beginSpec.Clauses().v) {
@@ -1254,7 +1251,7 @@ void OmpStructureChecker::Enter(const parser::OpenMPSectionsConstruct &x) {
std::get<parser::Block>(section.t), beginName.v, beginName.source);
}
HasInvalidWorksharingNesting(
- beginName.source, llvm::omp::nestedWorkshareErrSet,beginSpec.DirId());
+ beginName.source, llvm::omp::nestedWorkshareErrSet, beginSpec.DirId());
}
void OmpStructureChecker::Leave(const parser::OpenMPSectionsConstruct &) {
diff --git a/flang/lib/Semantics/check-omp-structure.h b/flang/lib/Semantics/check-omp-structure.h
index 8afbfd6a6aab2..c5c84593b73df 100644
--- a/flang/lib/Semantics/check-omp-structure.h
+++ b/flang/lib/Semantics/check-omp-structure.h
@@ -192,9 +192,8 @@ class OmpStructureChecker : public OmpStructureCheckerBase {
void CheckMultListItems();
void CheckStructureComponent(
const parser::OmpObjectList &objects, llvm::omp::Clause clauseId);
- bool HasInvalidWorksharingNesting(
- const parser::CharBlock &, const OmpDirectiveSet &,
- llvm::omp::Directive directive);
+ bool HasInvalidWorksharingNesting(const parser::CharBlock &,
+ const OmpDirectiveSet &, llvm::omp::Directive directive);
bool IsCloselyNestedRegion(const OmpDirectiveSet &set);
bool IsNestedInDirective(llvm::omp::Directive directive);
bool IsCombinedParallelWorksharing(llvm::omp::Directive directive) const;
diff --git a/flang/test/Semantics/OpenMP/nested_parallel_sections_valid.f90 b/flang/test/Semantics/OpenMP/nested_parallel_sections_valid.f90
new file mode 100644
index 0000000000000..0c57fe2b4ef78
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/nested_parallel_sections_valid.f90
@@ -0,0 +1,60 @@
+! RUN: %flang -fopenmp -c %s
+! Regression test for nested PARALLEL SECTIONS
+! This test verifies that combined parallel-worksharing constructs
+! can be properly nested as they create their own implicit parallel regions.
+
+program test_parallel_sections_nesting
+ implicit none
+ integer :: i, j, n
+ real :: a(10), b(10), c(10)
+
+ n = 10
+
+ ! Test 1: PARALLEL SECTIONS nesting PARALLEL SECTIONS
+ !$OMP PARALLEL SECTIONS
+ !$OMP SECTION
+ !$OMP PARALLEL SECTIONS
+ !$OMP SECTION
+ do i = 1, n
+ a(i) = real(i)
+ end do
+ !$OMP SECTION
+ do j = 1, n
+ b(j) = real(j * 2)
+ end do
+ !$OMP END PARALLEL SECTIONS
+ !$OMP SECTION
+ !$OMP PARALLEL DO
+ do i = 1, n
+ c(i) = a(i) + b(i)
+ end do
+ !$OMP END PARALLEL DO
+ !$OMP END PARALLEL SECTIONS
+
+ ! Test 2: PARALLEL SECTIONS inside PARALLEL
+ !$OMP PARALLEL
+ !$OMP PARALLEL SECTIONS
+ !$OMP SECTION
+ do i = 1, n
+ a(i) = a(i) * 2
+ end do
+ !$OMP SECTION
+ do j = 1, n
+ b(j) = b(j) * 2
+ end do
+ !$OMP END PARALLEL SECTIONS
+ !$OMP END PARALLEL
+
+ ! Test 3: PARALLEL DO inside PARALLEL SECTIONS
+ !$OMP PARALLEL SECTIONS
+ !$OMP SECTION
+ !$OMP PARALLEL DO
+ do i = 1, n
+ c(i) = c(i) + a(i)
+ end do
+ !$OMP END PARALLEL DO
+ !$OMP SECTION
+ c = c + 1.0
+ !$OMP END PARALLEL SECTIONS
+
+end program test_parallel_sections_nesting
\ No newline at end of file
diff --git a/flang/test/Semantics/OpenMP/workshare04.f90 b/flang/test/Semantics/OpenMP/workshare04.f90
index 0ec635e52d2b7..e5d6334eaf373 100644
--- a/flang/test/Semantics/OpenMP/workshare04.f90
+++ b/flang/test/Semantics/OpenMP/workshare04.f90
@@ -18,7 +18,6 @@ subroutine omp_workshare(aa, bb, cc, dd, ee, ff, n)
!$omp end parallel
!ERROR: OpenMP constructs enclosed in WORKSHARE construct may consist of ATOMIC, CRITICAL or PARALLEL constructs only
- !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
!$omp parallel workshare
!ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
!$omp single
diff --git a/flang/test/Semantics/OpenMP/workshare05.f90 b/flang/test/Semantics/OpenMP/workshare05.f90
index b57053e092e67..0bee882341342 100644
--- a/flang/test/Semantics/OpenMP/workshare05.f90
+++ b/flang/test/Semantics/OpenMP/workshare05.f90
@@ -40,7 +40,7 @@ program omp_workshare
!$omp end single
!$omp end parallel
- !ERROR: A worksharing region may not be closely nested inside a worksharing, explicit task, taskloop, critical, ordered, atomic, or master region
+
!$omp parallel sections
!$omp section
aa = my_func()
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