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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);
Expand Down
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"> {
Expand Down
65 changes: 46 additions & 19 deletions flang/lib/Optimizer/Transforms/FIRToSCF.cpp
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Expand Up @@ -25,11 +25,18 @@ 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 {
mlir::Location loc = doLoopOp.getLoc();
bool hasFinalValue = doLoopOp.getFinalValue().has_value();
bool isUnordered = doLoopOp.getUnordered().has_value();

// Get loop values from the DoLoopOp
mlir::Value low = doLoopOp.getLowerBound();
Expand All @@ -53,39 +60,54 @@ struct DoLoopConversion : public mlir::OpRewritePattern<fir::DoLoopOp> {
mlir::arith::DivSIOp::create(rewriter, loc, distance, step);
auto zero = mlir::arith::ConstantIndexOp::create(rewriter, loc, 0);
auto one = mlir::arith::ConstantIndexOp::create(rewriter, loc, 1);
auto scfForOp =
mlir::scf::ForOp::create(rewriter, loc, zero, tripCount, one, iterArgs);

// Create the scf.for or scf.parallel operation
mlir::Operation *scfLoopOp = nullptr;
if (isUnordered && parallelUnorderedLoop) {
scfLoopOp = mlir::scf::ParallelOp::create(rewriter, loc, {zero},
{tripCount}, {one}, iterArgs);
} else {
scfLoopOp = mlir::scf::ForOp::create(rewriter, loc, zero, tripCount, one,
iterArgs);
}

// Move the body of the fir.do_loop to the scf.for or scf.parallel
auto &loopOps = doLoopOp.getBody()->getOperations();
auto resultOp =
mlir::cast<fir::ResultOp>(doLoopOp.getBody()->getTerminator());
auto results = resultOp.getOperands();
mlir::Block *loweredBody = scfForOp.getBody();
auto scfLoopLikeOp = mlir::cast<mlir::LoopLikeOpInterface>(scfLoopOp);
mlir::Block &scfLoopBody = scfLoopLikeOp.getLoopRegions().front()->front();

loweredBody->getOperations().splice(loweredBody->begin(), loopOps,
loopOps.begin(),
std::prev(loopOps.end()));
scfLoopBody.getOperations().splice(scfLoopBody.begin(), loopOps,
loopOps.begin(),
std::prev(loopOps.end()));

rewriter.setInsertionPointToStart(loweredBody);
rewriter.setInsertionPointToStart(&scfLoopBody);
mlir::Value iv = mlir::arith::MulIOp::create(
rewriter, loc, scfForOp.getInductionVar(), step);
rewriter, loc, scfLoopLikeOp.getSingleInductionVar().value(), step);
iv = mlir::arith::AddIOp::create(rewriter, loc, low, iv);

if (!results.empty()) {
rewriter.setInsertionPointToEnd(loweredBody);
rewriter.setInsertionPointToEnd(&scfLoopBody);
mlir::scf::YieldOp::create(rewriter, resultOp->getLoc(), results);
}
doLoopOp.getInductionVar().replaceAllUsesWith(iv);
rewriter.replaceAllUsesWith(doLoopOp.getRegionIterArgs(),
hasFinalValue
? scfForOp.getRegionIterArgs().drop_front()
: scfForOp.getRegionIterArgs());

// Copy all the attributes from the old to new op.
scfForOp->setAttrs(doLoopOp->getAttrs());
rewriter.replaceOp(doLoopOp, scfForOp);
rewriter.replaceAllUsesWith(
doLoopOp.getRegionIterArgs(),
hasFinalValue ? scfLoopLikeOp.getRegionIterArgs().drop_front()
: scfLoopLikeOp.getRegionIterArgs());

// Copy loop annotations from the fir.do_loop to scf loop op.
if (auto ann = doLoopOp.getLoopAnnotation())
scfLoopOp->setAttr("loop_annotation", *ann);

rewriter.replaceOp(doLoopOp, scfLoopOp);
return mlir::success();
}

private:
bool parallelUnorderedLoop;
};

struct IterWhileConversion : public mlir::OpRewritePattern<fir::IterWhileOp> {
Expand Down Expand Up @@ -197,10 +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));
}

Expand Down
57 changes: 54 additions & 3 deletions flang/test/Fir/FirToSCF/do-loop.fir
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
// RUN: fir-opt %s --fir-to-scf | 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 @@ -31,6 +32,8 @@ func.func @simple_loop(%arg0: !fir.ref<!fir.array<100xi32>>) {
return
}

// -----

// CHECK-LABEL: func.func @loop_with_negtive_step(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>) {
// CHECK: %[[VAL_0:.*]] = arith.constant 100 : index
Expand Down Expand Up @@ -64,6 +67,8 @@ func.func @loop_with_negtive_step(%arg0: !fir.ref<!fir.array<100xi32>>) {
return
}

// -----

// CHECK-LABEL: func.func @loop_with_results(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>,
// CHECK-SAME: %[[ARG1:.*]]: !fir.ref<i32>) {
Expand Down Expand Up @@ -102,6 +107,8 @@ func.func @loop_with_results(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !fir.r
return
}

// -----

// CHECK-LABEL: func.func @loop_with_final_value(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>,
// CHECK-SAME: %[[ARG1:.*]]: !fir.ref<i32>) {
Expand Down Expand Up @@ -146,6 +153,45 @@ func.func @loop_with_final_value(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !f
return
}

// -----

// CHECK-LABEL: func.func @loop_with_unordered_attr(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>) {
// CHECK: %[[CONSTANT_0:.*]] = arith.constant 1 : index
// CHECK: %[[CONSTANT_1:.*]] = arith.constant 100 : index
// CHECK: %[[SHAPE_0:.*]] = fir.shape %[[CONSTANT_1]] : (index) -> !fir.shape<1>
// CHECK: %[[CONSTANT_2:.*]] = arith.constant 1 : i32
// CHECK: %[[SUBI_0:.*]] = arith.subi %[[CONSTANT_1]], %[[CONSTANT_0]] : index
// CHECK: %[[ADDI_0:.*]] = arith.addi %[[SUBI_0]], %[[CONSTANT_0]] : index
// CHECK: %[[DIVSI_0:.*]] = arith.divsi %[[ADDI_0]], %[[CONSTANT_0]] : index
// CHECK: %[[CONSTANT_3:.*]] = arith.constant 0 : index
// CHECK: %[[CONSTANT_4:.*]] = arith.constant 1 : index
// 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>
// PARALLEL: scf.reduce
// CHECK: }
// CHECK: return
// CHECK: }
func.func @loop_with_unordered_attr(%arg0: !fir.ref<!fir.array<100xi32>>) {
%c1 = arith.constant 1 : index
%c100 = arith.constant 100 : index
%0 = fir.shape %c100 : (index) -> !fir.shape<1>
%c1_i32 = arith.constant 1 : i32
fir.do_loop %arg1 = %c1 to %c100 step %c1 unordered {
%1 = fir.array_coor %arg0(%0) %arg1 : (!fir.ref<!fir.array<100xi32>>, !fir.shape<1>, index) -> !fir.ref<i32>
fir.store %c1_i32 to %1 : !fir.ref<i32>
}
return
}

// -----

// CHECK: #[[$ATTR_0:.+]] = #llvm.loop_vectorize<disable = false>
// CHECK: #[[$ATTR_1:.+]] = #llvm.loop_annotation<vectorize = #[[$ATTR_0]]>
// CHECK-LABEL: func.func @loop_with_attribute(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100xi32>>,
// CHECK-SAME: %[[ARG1:.*]]: !fir.ref<i32>) {
Expand All @@ -167,16 +213,19 @@ func.func @loop_with_final_value(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !f
// CHECK: %[[VAL_15:.*]] = fir.load %[[VAL_3]] : !fir.ref<i32>
// CHECK: %[[VAL_16:.*]] = arith.addi %[[VAL_15]], %[[VAL_14]] : i32
// CHECK: fir.store %[[VAL_16]] to %[[VAL_3]] : !fir.ref<i32>
// CHECK: } {operandSegmentSizes = array<i32: 1, 1, 1, 1, 0>, reduceAttrs = [#fir.reduce_attr<add>]}
// CHECK: } {loop_annotation = #[[$ATTR_1]]}
// CHECK: return
// CHECK: }

#loop_vectorize = #llvm.loop_vectorize<disable = false>
#loop_annotation = #llvm.loop_annotation<vectorize = #loop_vectorize>
func.func @loop_with_attribute(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !fir.ref<i32>) {
%c1 = arith.constant 1 : index
%c0_i32 = arith.constant 0 : i32
%c100 = arith.constant 100 : index
%0 = fir.alloca i32
%1 = fir.shape %c100 : (index) -> !fir.shape<1>
fir.do_loop %arg2 = %c1 to %c100 step %c1 reduce(#fir.reduce_attr<add> -> %0 : !fir.ref<i32>) {
fir.do_loop %arg2 = %c1 to %c100 step %c1 attributes {loopAnnotation = #loop_annotation} {
%2 = fir.array_coor %arg0(%1) %arg2 : (!fir.ref<!fir.array<100xi32>>, !fir.shape<1>, index) -> !fir.ref<i32>
%3 = fir.load %2 : !fir.ref<i32>
%4 = fir.load %0 : !fir.ref<i32>
Expand All @@ -187,6 +236,8 @@ func.func @loop_with_attribute(%arg0: !fir.ref<!fir.array<100xi32>>, %arg1: !fir
return
}

// -----

// CHECK-LABEL: func.func @nested_loop(
// CHECK-SAME: %[[ARG0:.*]]: !fir.ref<!fir.array<100x100xi32>>) {
// CHECK: %[[VAL_0:.*]] = arith.constant 1 : index
Expand Down