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[flang][OpenMP] Canonicalize loops with intervening OpenMP constructs #169191

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Nov 22, 2025
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[flang][OpenMP] Canonicalize loops with intervening OpenMP constructs #169191

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1 change: 1 addition & 0 deletions flang/include/flang/Parser/openmp-utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,7 @@ template <typename T> struct IsStatement<Statement<T>> {
};

std::optional<Label> GetStatementLabel(const ExecutionPartConstruct &x);
std::optional<Label> GetFinalLabel(const OpenMPConstruct &x);

const OmpObjectList *GetOmpObjectList(const OmpClause &clause);

Expand Down
39 changes: 39 additions & 0 deletions flang/lib/Parser/openmp-utils.cpp
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Expand Up @@ -15,6 +15,7 @@
#include "flang/Common/indirection.h"
#include "flang/Common/template.h"
#include "flang/Common/visit.h"
#include "flang/Parser/tools.h"

#include <tuple>
#include <type_traits>
Expand Down Expand Up @@ -77,6 +78,44 @@ std::optional<Label> GetStatementLabel(const ExecutionPartConstruct &x) {
return GetStatementLabelHelper(x);
}

static std::optional<Label> GetFinalLabel(const Block &x) {
if (!x.empty()) {
const ExecutionPartConstruct &last{x.back()};
if (auto *omp{Unwrap<OpenMPConstruct>(last)}) {
return GetFinalLabel(*omp);
} else if (auto *doLoop{Unwrap<DoConstruct>(last)}) {
return GetFinalLabel(std::get<Block>(doLoop->t));
} else {
return GetStatementLabel(x.back());
}
} else {
return std::nullopt;
}
}

std::optional<Label> GetFinalLabel(const OpenMPConstruct &x) {
return common::visit(
[](auto &&s) -> std::optional<Label> {
using TypeS = llvm::remove_cvref_t<decltype(s)>;
if constexpr (std::is_same_v<TypeS, OpenMPSectionsConstruct>) {
auto &list{std::get<std::list<OpenMPConstruct>>(s.t)};
if (!list.empty()) {
return GetFinalLabel(list.back());
} else {
return std::nullopt;
}
} else if constexpr ( //
std::is_same_v<TypeS, OpenMPLoopConstruct> ||
std::is_same_v<TypeS, OpenMPSectionConstruct> ||
std::is_base_of_v<OmpBlockConstruct, TypeS>) {
return GetFinalLabel(std::get<Block>(s.t));
} else {
return std::nullopt;
}
},
x.u);
}

const OmpObjectList *GetOmpObjectList(const OmpClause &clause) {
// Clauses with OmpObjectList as its data member
using MemberObjectListClauses = std::tuple<OmpClause::Copyin,
Expand Down
17 changes: 14 additions & 3 deletions flang/lib/Semantics/canonicalize-do.cpp
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Expand Up @@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//

#include "canonicalize-do.h"
#include "flang/Parser/openmp-utils.h"
#include "flang/Parser/parse-tree-visitor.h"

namespace Fortran::parser {
Expand Down Expand Up @@ -87,6 +88,12 @@ class CanonicalizationOfDoLoops {
[&](Statement<ActionStmt> &actionStmt) {
CanonicalizeIfMatch(block, stack, i, actionStmt);
},
[&](common::Indirection<OpenMPConstruct> &construct) {
// If the body of the OpenMP construct ends with a label,
// treat the label as ending the construct itself.
CanonicalizeIfMatch(
block, stack, i, omp::GetFinalLabel(construct.value()));
},
},
executableConstruct->u);
}
Expand All @@ -97,10 +104,14 @@ class CanonicalizationOfDoLoops {
template <typename T>
void CanonicalizeIfMatch(Block &originalBlock, std::vector<LabelInfo> &stack,
Block::iterator &i, Statement<T> &statement) {
if (!stack.empty() && statement.label &&
stack.back().label == *statement.label) {
CanonicalizeIfMatch(originalBlock, stack, i, statement.label);
}

void CanonicalizeIfMatch(Block &originalBlock, std::vector<LabelInfo> &stack,
Block::iterator &i, std::optional<Label> label) {
if (!stack.empty() && label && stack.back().label == *label) {
auto currentLabel{stack.back().label};
if constexpr (std::is_same_v<T, common::Indirection<EndDoStmt>>) {
if (Unwrap<EndDoStmt>(*i)) {
std::get<ExecutableConstruct>(i->u).u = Statement<ActionStmt>{
std::optional<Label>{currentLabel}, ContinueStmt{}};
}
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39 changes: 39 additions & 0 deletions flang/test/Parser/OpenMP/atomic-label-do.f90
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@@ -0,0 +1,39 @@
!RUN: %flang_fc1 -fdebug-unparse -fopenmp %s | FileCheck --ignore-case --check-prefix="UNPARSE" %s
!RUN: %flang_fc1 -fdebug-dump-parse-tree -fopenmp %s | FileCheck --check-prefix="PARSE-TREE" %s

subroutine f
integer :: i, x
do 100 i = 1, 10
!$omp atomic write
100 x = i
end

!UNPARSE: SUBROUTINE f
!UNPARSE: INTEGER i, x
!UNPARSE: DO i=1_4,10_4
!UNPARSE: !$OMP ATOMIC WRITE
!UNPARSE: 100 x=i
!UNPARSE: END DO
!UNPARSE: END SUBROUTINE

!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> DoConstruct
!PARSE-TREE: | NonLabelDoStmt
!PARSE-TREE: | | LoopControl -> LoopBounds
!PARSE-TREE: | | | Scalar -> Name = 'i'
!PARSE-TREE: | | | Scalar -> Expr = '1_4'
!PARSE-TREE: | | | | LiteralConstant -> IntLiteralConstant = '1'
!PARSE-TREE: | | | Scalar -> Expr = '10_4'
!PARSE-TREE: | | | | LiteralConstant -> IntLiteralConstant = '10'
!PARSE-TREE: | Block
!PARSE-TREE: | | ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAtomicConstruct
!PARSE-TREE: | | | OmpBeginDirective
!PARSE-TREE: | | | | OmpDirectiveName -> llvm::omp::Directive = atomic
!PARSE-TREE: | | | | OmpClauseList -> OmpClause -> Write
!PARSE-TREE: | | | | Flags = None
!PARSE-TREE: | | | Block
!PARSE-TREE: | | | | ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> AssignmentStmt = 'x=i'
!PARSE-TREE: | | | | | Variable = 'x'
!PARSE-TREE: | | | | | | Designator -> DataRef -> Name = 'x'
!PARSE-TREE: | | | | | Expr = 'i'
!PARSE-TREE: | | | | | | Designator -> DataRef -> Name = 'i'
!PARSE-TREE: | EndDoStmt ->
48 changes: 48 additions & 0 deletions flang/test/Parser/OpenMP/cross-label-do.f90
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@@ -0,0 +1,48 @@
!RUN: %flang_fc1 -fdebug-unparse -fopenmp %s | FileCheck --ignore-case --check-prefix="UNPARSE" %s
!RUN: %flang_fc1 -fdebug-dump-parse-tree -fopenmp %s | FileCheck --check-prefix="PARSE-TREE" %s

subroutine f00
integer :: i, j
do 100 i = 1,10
!$omp do
do 100 j = 1,10
100 continue
end

!UNPARSE: SUBROUTINE f00
!UNPARSE: INTEGER i, j
!UNPARSE: DO i=1_4,10_4
!UNPARSE: !$OMP DO
!UNPARSE: DO j=1_4,10_4
!UNPARSE: 100 CONTINUE
!UNPARSE: END DO
!UNPARSE: END DO
!UNPARSE: END SUBROUTINE

!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> DoConstruct
!PARSE-TREE: | NonLabelDoStmt
!PARSE-TREE: | | LoopControl -> LoopBounds
!PARSE-TREE: | | | Scalar -> Name = 'i'
!PARSE-TREE: | | | Scalar -> Expr = '1_4'
!PARSE-TREE: | | | | LiteralConstant -> IntLiteralConstant = '1'
!PARSE-TREE: | | | Scalar -> Expr = '10_4'
!PARSE-TREE: | | | | LiteralConstant -> IntLiteralConstant = '10'
!PARSE-TREE: | Block
!PARSE-TREE: | | ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPLoopConstruct
!PARSE-TREE: | | | OmpBeginLoopDirective
!PARSE-TREE: | | | | OmpDirectiveName -> llvm::omp::Directive = do
!PARSE-TREE: | | | | OmpClauseList ->
!PARSE-TREE: | | | | Flags = None
!PARSE-TREE: | | | Block
!PARSE-TREE: | | | | ExecutionPartConstruct -> ExecutableConstruct -> DoConstruct
!PARSE-TREE: | | | | | NonLabelDoStmt
!PARSE-TREE: | | | | | | LoopControl -> LoopBounds
!PARSE-TREE: | | | | | | | Scalar -> Name = 'j'
!PARSE-TREE: | | | | | | | Scalar -> Expr = '1_4'
!PARSE-TREE: | | | | | | | | LiteralConstant -> IntLiteralConstant = '1'
!PARSE-TREE: | | | | | | | Scalar -> Expr = '10_4'
!PARSE-TREE: | | | | | | | | LiteralConstant -> IntLiteralConstant = '10'
!PARSE-TREE: | | | | | Block
!PARSE-TREE: | | | | | | ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> ContinueStmt
!PARSE-TREE: | | | | | EndDoStmt ->
!PARSE-TREE: | EndDoStmt ->