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[flang][OpenMP] Remove ineffective atomic capture validation (issue #161934 deferred) #162884

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[flang][OpenMP] Remove ineffective atomic capture validation (issue #161934 deferred) #162884

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a9f7208
[Flang][OpenMP] Fix overly restrictive atomic capture validation
Oct 10, 2025
ad66daa
[flang][OpenMP] Remove ineffective atomic capture validation
Oct 13, 2025
3c44c16
Apply clang-format and remove unrelated whitespace change
Oct 13, 2025
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16 changes: 16 additions & 0 deletions flang/lib/Semantics/check-omp-atomic.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#include "flang/Evaluate/match.h"
#include "flang/Evaluate/rewrite.h"
#include "flang/Evaluate/tools.h"
#include "flang/Evaluate/traverse.h"
#include "flang/Parser/char-block.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Semantics/openmp-utils.h"
Expand Down Expand Up @@ -692,6 +693,15 @@ OmpStructureChecker::CheckUpdateCapture(
"In ATOMIC UPDATE operation with CAPTURE neither statement could be the update or the capture"_err_en_US);
}};

auto checkSameAtomicLocation{
[&](const evaluate::Assignment &upd, const evaluate::Assignment &cap) {
// For now, this is a placeholder. A complete implementation would need
// to walk the entire expression tree of upd.rhs to find all DataRef
// nodes and compare them structurally with the atomic variable
// (upd.lhs). This is complex and requires proper expression traversal.
// The MLIR verification layer catches these cases as a safety net.
}};

auto makeSelectionFromDet{[&](int det) -> ReturnTy {
// If det != 0, then the checks unambiguously suggest a specific
// categorization.
Expand All @@ -701,6 +711,7 @@ OmpStructureChecker::CheckUpdateCapture(
if (det > 0) {
// as1 is update, as2 is capture
if (isUpdateCapture(as1, as2)) {
checkSameAtomicLocation(as1, as2);
return std::make_pair(/*Update=*/ec1, /*Capture=*/ec2);
} else {
errorCaptureShouldRead(act2.source, as1.lhs.AsFortran());
Expand All @@ -709,6 +720,7 @@ OmpStructureChecker::CheckUpdateCapture(
} else if (det < 0) {
// as2 is update, as1 is capture
if (isUpdateCapture(as2, as1)) {
checkSameAtomicLocation(as2, as1);
return std::make_pair(/*Update=*/ec2, /*Capture=*/ec1);
} else {
errorCaptureShouldRead(act1.source, as2.lhs.AsFortran());
Expand All @@ -722,11 +734,15 @@ OmpStructureChecker::CheckUpdateCapture(
// capture, emit a warning about the ambiguity.
context_.Say(act1.source,
"In ATOMIC UPDATE operation with CAPTURE either statement could be the update and the capture, assuming the first one is the capture statement"_warn_en_US);
checkSameAtomicLocation(as2, as1);
return std::make_pair(/*Update=*/ec2, /*Capture=*/ec1);
}
if (updateFirst != captureFirst) {
const parser::ExecutionPartConstruct *upd{updateFirst ? ec1 : ec2};
const parser::ExecutionPartConstruct *cap{captureFirst ? ec1 : ec2};
const evaluate::Assignment &updAssign{updateFirst ? as1 : as2};
const evaluate::Assignment &capAssign{captureFirst ? as1 : as2};
checkSameAtomicLocation(updAssign, capAssign);
return std::make_pair(upd, cap);
}
assert(!updateFirst && !captureFirst);
Expand Down