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[Flang] Fix perfect loop nest detection #161554

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Merged
merged 2 commits into from
Oct 1, 2025
Merged

[Flang] Fix perfect loop nest detection #161554

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e7b1c2e
Unwrap block element
Meinersbur Oct 1, 2025
e8aa361
Fix comment
Meinersbur Oct 1, 2025
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13 changes: 8 additions & 5 deletions flang/lib/Semantics/resolve-directives.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2303,14 +2303,17 @@ void OmpAttributeVisitor::CheckPerfectNestAndRectangularLoop(
}

auto checkPerfectNest = [&, this]() {
auto blockSize = block.size();
if (blockSize <= 1)
if (block.empty())
return;
auto last = block.end();
--last;

if (parser::Unwrap<parser::ContinueStmt>(x))
blockSize -= 1;
// A trailing CONTINUE is not considered part of the loop body
if (parser::Unwrap<parser::ContinueStmt>(*last))
--last;

if (blockSize <= 1)
// In a perfectly nested loop, the nested loop must be the only statement
if (last == block.begin())
return;

// Non-perfectly nested loop
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19 changes: 19 additions & 0 deletions flang/test/Lower/OpenMP/wsloop-collapse-continue.f90
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@@ -0,0 +1,19 @@
! RUN: bbc -fopenmp -emit-hlfir %s -o - | FileCheck %s

program wsloop_collapse_continue
integer i, j

! CHECK: omp.wsloop {{.*}} {
! CHECK: omp.loop_nest ({{.*}}) : i32 = ({{.*}}) to ({{.*}}) inclusive step ({{.*}}) collapse(2) {
!$omp do collapse(2)
do 50 i = 1, 42
do 51 j = 1, 84
! CHECK: fir.call @_FortranAioOutputInteger32(
print *, i
! CHECK: fir.call @_FortranAioOutputInteger32(
print *, j
51 continue
50 continue
!$omp end do

end program wsloop_collapse_continue
1 change: 0 additions & 1 deletion flang/test/Semantics/OpenMP/do08.f90
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Expand Up @@ -61,7 +61,6 @@ program omp
!$omp end do


!ERROR: Canonical loop nest must be perfectly nested.
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These ERRORs were added in #60283. Those are still non-perfectly nested loops, but the other errors get precedence.

!ERROR: The value of the parameter in the COLLAPSE or ORDERED clause must not be larger than the number of nested loops following the construct.
!$omp do collapse(3)
do 60 i=2,200,2
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1 change: 0 additions & 1 deletion flang/test/Semantics/OpenMP/do13.f90
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Expand Up @@ -59,7 +59,6 @@ program omp
!$omp end do


!ERROR: Canonical loop nest must be perfectly nested.
!ERROR: The value of the parameter in the COLLAPSE or ORDERED clause must not be larger than the number of nested loops following the construct.
!$omp do collapse(3)
do 60 i=1,10
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