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[flang][OpenMP] Avoid analyzing assumed-size array bases (#150324)

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A check for character substrings masquerading as array sections was
using expression analyzer on the array base. When this array happened to
be an assumed-size array, the analyzer emitted a semantic error that did
not correspond to any issue with the source code.

To avoid that, check whether the object is an assumed-size array before
using the expression analyzer on it.

While at it, replace the call to GetShape with a simple check for rank,
since that's the only information needed.

Fixes https://github.com/llvm/llvm-project/issues/150297

(cherry picked from commit 8fcbd06b25fd0c1b4bc4a4c8775129f7dab1affd)
This commit is contained in:
Krzysztof Parzyszek 2025-07-24 07:27:00 -05:00 committed by Tobias Hieta
parent 704f542b3d
commit 9554152c8a
2 changed files with 45 additions and 16 deletions
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36
flang/lib/Semantics/check-omp-structure.cpp
View File

@ -16,7 +16,6 @@
#include "flang/Common/idioms.h"
#include "flang/Common/indirection.h"
#include "flang/Common/visit.h"
#include "flang/Evaluate/shape.h"
#include "flang/Evaluate/tools.h"
#include "flang/Evaluate/type.h"
#include "flang/Parser/char-block.h"
@ -4117,21 +4116,26 @@ void OmpStructureChecker::CheckArraySection(
// Detect this by looking for array accesses on character variables which are
// not arrays.
bool isSubstring{false};
evaluate::ExpressionAnalyzer ea{context_};
if (MaybeExpr expr = ea.Analyze(arrayElement.base)) {
std::optional<evaluate::Shape> shape = evaluate::GetShape(expr);
// Not an array: rank 0
if (shape && shape->size() == 0) {
if (std::optional<evaluate::DynamicType> type = expr->GetType()) {
if (type->category() == evaluate::TypeCategory::Character) {
// Substrings are explicitly denied by the standard [6.0:163:9-11].
// This is supported as an extension. This restriction was added in
// OpenMP 5.2.
isSubstring = true;
context_.Say(GetContext().clauseSource,
"The use of substrings in OpenMP argument lists has been disallowed since OpenMP 5.2."_port_en_US);
} else {
llvm_unreachable("Array indexing on a variable that isn't an array");
// Cannot analyze a base of an assumed-size array on its own. If we know
// this is an array (assumed-size or not) we can ignore it, since we're
// looking for strings.
if (!IsAssumedSizeArray(*name.symbol)) {
evaluate::ExpressionAnalyzer ea{context_};
if (MaybeExpr expr = ea.Analyze(arrayElement.base)) {
if (expr->Rank() == 0) {
// Not an array: rank 0
if (std::optional<evaluate::DynamicType> type = expr->GetType()) {
if (type->category() == evaluate::TypeCategory::Character) {
// Substrings are explicitly denied by the standard [6.0:163:9-11].
// This is supported as an extension. This restriction was added in
// OpenMP 5.2.
isSubstring = true;
context_.Say(GetContext().clauseSource,
"The use of substrings in OpenMP argument lists has been disallowed since OpenMP 5.2."_port_en_US);
} else {
llvm_unreachable(
"Array indexing on a variable that isn't an array");
}
}
}
}

25
flang/test/Semantics/OpenMP/assumed-size-array.f90 Normal file
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@ -0,0 +1,25 @@
!RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
! This should compile without errors. Check for a symptom of a reasonable
! output.
!CHECK: omp.task depend
subroutine omp_task_depend_reproducer(work, myid, shift)
implicit none
integer, intent(in) :: myid, shift
real, intent(inout) :: work(*)
!$omp parallel shared(work, myid, shift)
!$omp single
!$omp task depend(in:work(myid+shift-1)) depend(in:work(myid-1)) depend(out:work(myid))
call dummy_kernel(work(myid))
!$omp end task
!$omp end single
!$omp end parallel
contains
subroutine dummy_kernel(x)
real :: x
x = x + 1.0
end subroutine dummy_kernel
end subroutine omp_task_depend_reproducer