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[MLIR] Fix SCF loop specialization (peeling) to work on scf.for with non-index type #158707

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Merged
merged 1 commit into from
Sep 16, 2025
Merged

[MLIR] Fix SCF loop specialization (peeling) to work on scf.for with non-index type #158707

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10 changes: 9 additions & 1 deletion mlir/lib/Dialect/SCF/Transforms/LoopSpecialization.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,9 @@ static void specializeForLoopForUnrolling(ForOp op) {

OpBuilder b(op);
IRMapping map;
Value constant = arith::ConstantIndexOp::create(b, op.getLoc(), minConstant);
Value constant = arith::ConstantOp::create(
b, op.getLoc(),
IntegerAttr::get(op.getUpperBound().getType(), minConstant));
Value cond = arith::CmpIOp::create(b, op.getLoc(), arith::CmpIPredicate::eq,
bound, constant);
map.map(bound, constant);
Expand Down Expand Up @@ -150,6 +152,9 @@ static LogicalResult peelForLoop(RewriterBase &b, ForOp forOp,
ValueRange{forOp.getLowerBound(),
forOp.getUpperBound(),
forOp.getStep()});
if (splitBound.getType() != forOp.getLowerBound().getType())
splitBound = b.createOrFold<arith::IndexCastOp>(
loc, forOp.getLowerBound().getType(), splitBound);

// Create ForOp for partial iteration.
b.setInsertionPointAfter(forOp);
Expand Down Expand Up @@ -230,6 +235,9 @@ LogicalResult mlir::scf::peelForLoopFirstIteration(RewriterBase &b, ForOp forOp,
auto loc = forOp.getLoc();
Value splitBound = b.createOrFold<AffineApplyOp>(
loc, ubMap, ValueRange{forOp.getLowerBound(), forOp.getStep()});
if (splitBound.getType() != forOp.getUpperBound().getType())
splitBound = b.createOrFold<arith::IndexCastOp>(
loc, forOp.getUpperBound().getType(), splitBound);

// Peel the first iteration.
IRMapping map;
Expand Down
35 changes: 35 additions & 0 deletions mlir/test/Dialect/SCF/for-loop-peeling.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,41 @@ func.func @fully_static_bounds() -> i32 {

// -----

// CHECK: func @fully_static_bounds_integers(
// CHECK-DAG: %[[C0:.*]] = arith.constant 0 : i32
// CHECK-DAG: %[[C1:.*]] = arith.constant 1 : i32
// CHECK-DAG: %[[C4:.*]] = arith.constant 4 : i32
// CHECK-DAG: %[[C16:.*]] = arith.constant 16 : i32
// CHECK: %[[LOOP:.*]] = scf.for %[[IV:.*]] = %[[C0]] to %[[C16]]
// CHECK-SAME: step %[[C4]] iter_args(%[[ACC:.*]] = %[[C0]]) -> (i32)
// CHECK: %[[MAP:.*]] = affine.min
// CHECK: %[[MAP_CAST:.*]] = arith.index_cast %[[MAP]]
// CHECK: %[[ADD:.*]] = arith.addi %[[ACC]], %[[MAP_CAST]] : i32
// CHECK: scf.yield %[[ADD]]
// CHECK: }
// CHECK: %[[RESULT:.*]] = arith.addi %[[LOOP]], %[[C1]] : i32
// CHECK: return %[[RESULT]]
#map = affine_map<(d0, d1)[s0] -> (s0, d0 - d1)>
func.func @fully_static_bounds_integers() -> i32 {
%c0_i32 = arith.constant 0 : i32
%lb = arith.constant 0 : i32
%step = arith.constant 4 : i32
%ub = arith.constant 17 : i32
%r = scf.for %iv = %lb to %ub step %step
iter_args(%arg = %c0_i32) -> i32 : i32 {
%ub_index = arith.index_cast %ub : i32 to index
%iv_index = arith.index_cast %iv : i32 to index
%step_index = arith.index_cast %step : i32 to index
%s = affine.min #map(%ub_index, %iv_index)[%step_index]
%casted = arith.index_cast %s : index to i32
%0 = arith.addi %arg, %casted : i32
scf.yield %0 : i32
}
return %r : i32
}

// -----

// CHECK-DAG: #[[MAP0:.*]] = affine_map<()[s0] -> ((s0 floordiv 4) * 4)>
// CHECK-DAG: #[[MAP1:.*]] = affine_map<(d0)[s0] -> (-d0 + s0)>
// CHECK: func @dynamic_upper_bound(
Expand Down