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[flang][fir] Convert fir.do_loop with the unordered attribute to scf.parallel. #168510

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Merged
NexMing merged 4 commits into from
Nov 25, 2025
Merged

[flang][fir] Convert fir.do_loop with the unordered attribute to scf.parallel. #168510

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316714c
[flang][fir] Convert `fir.do_loop` with the unordered attribute to `s…
NexMing Nov 18, 2025
45a330f
Only keep attributes that are valid for scf loop op.
NexMing Nov 18, 2025
1446f96
Add an option to control this conversion.
NexMing Nov 21, 2025
4cb2853
[NFC] Update comments.
NexMing Nov 25, 2025
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3 changes: 3 additions & 0 deletions flang/include/flang/Optimizer/Transforms/Passes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,9 @@ std::unique_ptr<mlir::Pass> createVScaleAttrPass();
std::unique_ptr<mlir::Pass>
createVScaleAttrPass(std::pair<unsigned, unsigned> vscaleAttr);

void populateFIRToSCFRewrites(mlir::RewritePatternSet &patterns,
bool parallelUnordered = false);

void populateCfgConversionRewrites(mlir::RewritePatternSet &patterns,
bool forceLoopToExecuteOnce = false,
bool setNSW = true);
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4 changes: 4 additions & 0 deletions flang/include/flang/Optimizer/Transforms/Passes.td
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Expand Up @@ -85,6 +85,10 @@ def FIRToSCFPass : Pass<"fir-to-scf"> {
let dependentDialects = [
"fir::FIROpsDialect", "mlir::scf::SCFDialect"
];
let options = [Option<"parallelUnordered", "parallel-unordered", "bool",
/*default=*/"false",
"Whether to convert `fir.do_loop` with the unordered "
"attribute to `scf.parallel`. Defaults to false.">];
}

def AnnotateConstantOperands : Pass<"annotate-constant"> {
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20 changes: 17 additions & 3 deletions flang/lib/Optimizer/Transforms/FIRToSCF.cpp
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Expand Up @@ -25,6 +25,12 @@ class FIRToSCFPass : public fir::impl::FIRToSCFPassBase<FIRToSCFPass> {
struct DoLoopConversion : public mlir::OpRewritePattern<fir::DoLoopOp> {
using OpRewritePattern<fir::DoLoopOp>::OpRewritePattern;

DoLoopConversion(mlir::MLIRContext *context,
bool parallelUnorderedLoop = false,
mlir::PatternBenefit benefit = 1)
: OpRewritePattern<fir::DoLoopOp>(context, benefit),
parallelUnorderedLoop(parallelUnorderedLoop) {}

mlir::LogicalResult
matchAndRewrite(fir::DoLoopOp doLoopOp,
mlir::PatternRewriter &rewriter) const override {
Expand Down Expand Up @@ -57,7 +63,7 @@ struct DoLoopConversion : public mlir::OpRewritePattern<fir::DoLoopOp> {

// Create the scf.for or scf.parallel operation
mlir::Operation *scfLoopOp = nullptr;
if (isUnordered) {
if (isUnordered && parallelUnorderedLoop) {
scfLoopOp = mlir::scf::ParallelOp::create(rewriter, loc, {zero},
{tripCount}, {one}, iterArgs);
} else {
Expand Down Expand Up @@ -99,6 +105,9 @@ struct DoLoopConversion : public mlir::OpRewritePattern<fir::DoLoopOp> {
rewriter.replaceOp(doLoopOp, scfLoopOp);
return mlir::success();
}

private:
bool parallelUnorderedLoop;
};

struct IterWhileConversion : public mlir::OpRewritePattern<fir::IterWhileOp> {
Expand Down Expand Up @@ -210,10 +219,15 @@ struct IfConversion : public mlir::OpRewritePattern<fir::IfOp> {
};
} // namespace

void fir::populateFIRToSCFRewrites(mlir::RewritePatternSet &patterns,
bool parallelUnordered) {
patterns.add<IterWhileConversion, IfConversion>(patterns.getContext());
patterns.add<DoLoopConversion>(patterns.getContext(), parallelUnordered);
}

void FIRToSCFPass::runOnOperation() {
mlir::RewritePatternSet patterns(&getContext());
patterns.add<DoLoopConversion, IterWhileConversion, IfConversion>(
patterns.getContext());
fir::populateFIRToSCFRewrites(patterns, parallelUnordered);
walkAndApplyPatterns(getOperation(), std::move(patterns));
}

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8 changes: 5 additions & 3 deletions flang/test/Fir/FirToSCF/do-loop.fir
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@@ -1,4 +1,5 @@
// RUN: fir-opt %s --fir-to-scf --split-input-file | FileCheck %s
// RUN: fir-opt %s --fir-to-scf --split-input-file | FileCheck %s --check-prefixes=CHECK,NO-PARALLEL
// RUN: fir-opt %s --fir-to-scf='parallel-unordered' --split-input-file | FileCheck %s --check-prefixes=CHECK,PARALLEL

// CHECK-LABEL: func.func @simple_loop(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>) {
Expand Down Expand Up @@ -165,12 +166,13 @@ func.func @loop_with_final_value(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !f
// CHECK: %[[DIVSI_0:.*]] = arith.divsi %[[ADDI_0]], %[[CONSTANT_0]] : index
// CHECK: %[[CONSTANT_3:.*]] = arith.constant 0 : index
// CHECK: %[[CONSTANT_4:.*]] = arith.constant 1 : index
// CHECK: scf.parallel (%[[VAL_0:.*]]) = (%[[CONSTANT_3]]) to (%[[DIVSI_0]]) step (%[[CONSTANT_4]]) {
// PARALLEL: scf.parallel (%[[VAL_0:.*]]) = (%[[CONSTANT_3]]) to (%[[DIVSI_0]]) step (%[[CONSTANT_4]]) {
// NO-PARALLEL: scf.for %[[VAL_0:.*]] = %[[CONSTANT_3]] to %[[DIVSI_0]] step %[[CONSTANT_4]] {
// CHECK: %[[MULI_0:.*]] = arith.muli %[[VAL_0]], %[[CONSTANT_0]] : index
// CHECK: %[[ADDI_1:.*]] = arith.addi %[[CONSTANT_0]], %[[MULI_0]] : index
// CHECK: %[[ARRAY_COOR_0:.*]] = fir.array_coor %[[ARG0]](%[[SHAPE_0]]) %[[ADDI_1]] : (!fir.ref<!fir.array<100xi32>>, !fir.shape<1>, index) -> !fir.ref<i32>
// CHECK: fir.store %[[CONSTANT_2]] to %[[ARRAY_COOR_0]] : !fir.ref<i32>
// CHECK: scf.reduce
// PARALLEL: scf.reduce
// CHECK: }
// CHECK: return
// CHECK: }
Expand Down