Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Nov 25, 2025
Merged

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

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
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
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 3 additions & 0 deletions flang/include/flang/Optimizer/Transforms/Passes.h
View file
Open in desktop
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
View file
Open in desktop
Original file line number Diff line number Diff line change
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",
"Allow converting a fir.do_loop with the `unordered` "
"attribute to scf.parallel (experimental).">];
}

def AnnotateConstantOperands : Pass<"annotate-constant"> {
Expand Down
65 changes: 46 additions & 19 deletions flang/lib/Optimizer/Transforms/FIRToSCF.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
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
View file
Open in desktop
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