[flang-commits] [flang] 9cff3f5 - [flang][OpenMP] Tolerate compiler directives in loop constructs (#169346)
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Mon Nov 24 14:48:32 PST 2025
Author: Krzysztof Parzyszek
Date: 2025-11-24T16:48:27-06:00
New Revision: 9cff3f51d35c4273a48b987bdeddd10248ecb5e4
URL: https://github.com/llvm/llvm-project/commit/9cff3f51d35c4273a48b987bdeddd10248ecb5e4
DIFF: https://github.com/llvm/llvm-project/commit/9cff3f51d35c4273a48b987bdeddd10248ecb5e4.diff
LOG: [flang][OpenMP] Tolerate compiler directives in loop constructs (#169346)
PR168884 flagged compiler directives (!dir$ ...) inside OpenMP loop
constructs as errors. This caused some customer applications to fail to
compile (issue 169229).
Downgrade the error to a warning, and gracefully ignore compiler
directives when lowering loop constructs to MLIR.
Fixes https://github.com/llvm/llvm-project/issues/169229
Added:
flang/test/Semantics/OpenMP/compiler-directives-loop.f90
Modified:
flang/lib/Lower/OpenMP/Utils.cpp
flang/lib/Semantics/check-omp-loop.cpp
flang/lib/Semantics/resolve-directives.cpp
flang/test/Semantics/OpenMP/loop-association.f90
Removed:
################################################################################
diff --git a/flang/lib/Lower/OpenMP/Utils.cpp b/flang/lib/Lower/OpenMP/Utils.cpp
index 7d7a4869ab3a6..fed84eb4df071 100644
--- a/flang/lib/Lower/OpenMP/Utils.cpp
+++ b/flang/lib/Lower/OpenMP/Utils.cpp
@@ -796,6 +796,28 @@ static void processTileSizesFromOpenMPConstruct(
}
}
+static pft::Evaluation *getNestedDoConstruct(pft::Evaluation &eval) {
+ for (pft::Evaluation &nested : eval.getNestedEvaluations()) {
+ // In an OpenMPConstruct there can be compiler directives:
+ // 1 <<OpenMPConstruct>>
+ // 2 CompilerDirective: !unroll
+ // <<DoConstruct>> -> 8
+ if (nested.getIf<parser::CompilerDirective>())
+ continue;
+ // Within a DoConstruct, there can be compiler directives, plus
+ // there is a DoStmt before the body:
+ // <<DoConstruct>> -> 8
+ // 3 NonLabelDoStmt -> 7: do i = 1, n
+ // <<DoConstruct>> -> 7
+ if (nested.getIf<parser::NonLabelDoStmt>())
+ continue;
+ assert(nested.getIf<parser::DoConstruct>() &&
+ "Unexpected construct in the nested evaluations");
+ return &nested;
+ }
+ llvm_unreachable("Expected do loop to be in the nested evaluations");
+}
+
/// Populates the sizes vector with values if the given OpenMPConstruct
/// contains a loop construct with an inner tiling construct.
void collectTileSizesFromOpenMPConstruct(
@@ -818,7 +840,7 @@ int64_t collectLoopRelatedInfo(
int64_t numCollapse = 1;
// Collect the loops to collapse.
- lower::pft::Evaluation *doConstructEval = &eval.getFirstNestedEvaluation();
+ lower::pft::Evaluation *doConstructEval = getNestedDoConstruct(eval);
if (doConstructEval->getIf<parser::DoConstruct>()->IsDoConcurrent()) {
TODO(currentLocation, "Do Concurrent in Worksharing loop construct");
}
@@ -844,7 +866,7 @@ void collectLoopRelatedInfo(
fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
// Collect the loops to collapse.
- lower::pft::Evaluation *doConstructEval = &eval.getFirstNestedEvaluation();
+ lower::pft::Evaluation *doConstructEval = getNestedDoConstruct(eval);
if (doConstructEval->getIf<parser::DoConstruct>()->IsDoConcurrent()) {
TODO(currentLocation, "Do Concurrent in Worksharing loop construct");
}
@@ -885,9 +907,8 @@ void collectLoopRelatedInfo(
iv.push_back(bounds->name.thing.symbol);
loopVarTypeSize = std::max(loopVarTypeSize,
bounds->name.thing.symbol->GetUltimate().size());
- collapseValue--;
- doConstructEval =
- &*std::next(doConstructEval->getNestedEvaluations().begin());
+ if (--collapseValue)
+ doConstructEval = getNestedDoConstruct(*doConstructEval);
} while (collapseValue > 0);
convertLoopBounds(converter, currentLocation, result, loopVarTypeSize);
diff --git a/flang/lib/Semantics/check-omp-loop.cpp b/flang/lib/Semantics/check-omp-loop.cpp
index 6d83ee62c3b73..ef237a01d0f7a 100644
--- a/flang/lib/Semantics/check-omp-loop.cpp
+++ b/flang/lib/Semantics/check-omp-loop.cpp
@@ -267,7 +267,7 @@ void OmpStructureChecker::CheckNestedBlock(const parser::OpenMPLoopConstruct &x,
for (auto &stmt : body) {
if (auto *dir{parser::Unwrap<parser::CompilerDirective>(stmt)}) {
context_.Say(dir->source,
- "Compiler directives are not allowed inside OpenMP loop constructs"_err_en_US);
+ "Compiler directives are not allowed inside OpenMP loop constructs"_warn_en_US);
} else if (parser::Unwrap<parser::DoConstruct>(stmt)) {
++nestedCount;
} else if (auto *omp{parser::Unwrap<parser::OpenMPLoopConstruct>(stmt)}) {
diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 673ea4ef10e08..b992a4125ffcb 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -2419,13 +2419,6 @@ void OmpAttributeVisitor::PrivatizeAssociatedLoopIndexAndCheckLoopLevel(
}
}
CheckAssocLoopLevel(level, GetAssociatedClause());
- } else {
- unsigned version{context_.langOptions().OpenMPVersion};
- context_.Say(GetContext().directiveSource,
- "A DO loop must follow the %s directive"_err_en_US,
- parser::ToUpperCaseLetters(
- llvm::omp::getOpenMPDirectiveName(GetContext().directive, version)
- .str()));
}
}
}
diff --git a/flang/test/Semantics/OpenMP/compiler-directives-loop.f90 b/flang/test/Semantics/OpenMP/compiler-directives-loop.f90
new file mode 100644
index 0000000000000..48b9529c95dc2
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/compiler-directives-loop.f90
@@ -0,0 +1,21 @@
+!RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=60 %s -o - | FileCheck %s
+
+! Check that this compiles successfully, but not rely on any specific output.
+
+!CHECK: omp.parallel
+
+program omp_cdir_crash
+ implicit none
+ integer, parameter :: n = 10
+ real :: a(n)
+ integer :: i
+
+!$omp parallel do
+!dir$ unroll
+ do i = 1, n
+ a(i) = real(i)
+ end do
+!$omp end parallel do
+
+ print *, 'a(1)=', a(1), ' a(n)=', a(n)
+end program omp_cdir_crash
diff --git a/flang/test/Semantics/OpenMP/loop-association.f90 b/flang/test/Semantics/OpenMP/loop-association.f90
index 9c79a91429fdf..4e63cafb3fda1 100644
--- a/flang/test/Semantics/OpenMP/loop-association.f90
+++ b/flang/test/Semantics/OpenMP/loop-association.f90
@@ -33,10 +33,9 @@
END DO outer
! Accept directives between parallel do and actual loop.
- !ERROR: A DO loop must follow the PARALLEL DO directive
!$OMP PARALLEL DO
!WARNING: Unrecognized compiler directive was ignored [-Wignored-directive]
- !ERROR: Compiler directives are not allowed inside OpenMP loop constructs
+ !WARNING: Compiler directives are not allowed inside OpenMP loop constructs
!DIR$ VECTOR ALIGNED
DO 20 i=1,N
a = a + 0.5
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