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[SCF][PIPELINE] Handle the case when values from the peeled prologue may escape out of the loop #105755

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Aug 23, 2024
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[SCF][PIPELINE] Handle the case when values from the peeled prologue may escape out of the loop #105755

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20 changes: 15 additions & 5 deletions mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -268,7 +268,7 @@ cloneAndUpdateOperands(RewriterBase &rewriter, Operation *op,
}

void LoopPipelinerInternal::emitPrologue(RewriterBase &rewriter) {
// Initialize the iteration argument to the loop initiale values.
// Initialize the iteration argument to the loop initial values.
for (auto [arg, operand] :
llvm::zip(forOp.getRegionIterArgs(), forOp.getInitsMutable())) {
setValueMapping(arg, operand.get(), 0);
Expand Down Expand Up @@ -320,16 +320,26 @@ void LoopPipelinerInternal::emitPrologue(RewriterBase &rewriter) {
if (annotateFn)
annotateFn(newOp, PipeliningOption::PipelinerPart::Prologue, i);
for (unsigned destId : llvm::seq(unsigned(0), op->getNumResults())) {
setValueMapping(op->getResult(destId), newOp->getResult(destId),
i - stages[op]);
Value source = newOp->getResult(destId);
// If the value is a loop carried dependency update the loop argument
// mapping.
for (OpOperand &operand : yield->getOpOperands()) {
if (operand.get() != op->getResult(destId))
continue;
if (predicates[predicateIdx] &&
!forOp.getResult(operand.getOperandNumber()).use_empty()) {
// If the value is used outside the loop, we need to make sure we
// return the correct version of it.
Value prevValue = valueMapping
[forOp.getRegionIterArgs()[operand.getOperandNumber()]]
[i - stages[op]];
source = rewriter.create<arith::SelectOp>(
loc, predicates[predicateIdx], source, prevValue);
}
setValueMapping(forOp.getRegionIterArgs()[operand.getOperandNumber()],
newOp->getResult(destId), i - stages[op] + 1);
source, i - stages[op] + 1);
}
setValueMapping(op->getResult(destId), newOp->getResult(destId),
i - stages[op]);
}
}
}
Expand Down
26 changes: 17 additions & 9 deletions mlir/test/Dialect/SCF/loop-pipelining.mlir
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Expand Up @@ -703,18 +703,26 @@ func.func @distance_1_use(%A: memref<?xf32>, %result: memref<?xf32>) {
// -----

// NOEPILOGUE-LABEL: stage_0_value_escape(
func.func @stage_0_value_escape(%A: memref<?xf32>, %result: memref<?xf32>) {
func.func @stage_0_value_escape(%A: memref<?xf32>, %result: memref<?xf32>, %ub: index) {
%c0 = arith.constant 0 : index
%c1 = arith.constant 1 : index
%c4 = arith.constant 4 : index
%cf = arith.constant 1.0 : f32
// NOEPILOGUE: %[[C3:.+]] = arith.constant 3 : index
// NOEPILOGUE: %[[A:.+]] = arith.addf
// NOEPILOGUE: scf.for %[[IV:.+]] = {{.*}} iter_args(%[[ARG:.+]] = %[[A]],
// NOEPILOGUE: %[[C:.+]] = arith.cmpi slt, %[[IV]], %[[C3]] : index
// NOEPILOGUE: %[[S:.+]] = arith.select %[[C]], %{{.+}}, %[[ARG]] : f32
// NOEPILOGUE: scf.yield %[[S]]
%r = scf.for %i0 = %c0 to %c4 step %c1 iter_args(%arg0 = %cf) -> (f32) {
// NOEPILOGUE: %[[UB:[^,]+]]: index)
// NOEPILOGUE-DAG: %[[C0:.+]] = arith.constant 0 : index
// NOEPILOGUE-DAG: %[[C1:.+]] = arith.constant 1 : index
// NOEPILOGUE-DAG: %[[CF:.+]] = arith.constant 1.000000e+00
// NOEPILOGUE: %[[CND0:.+]] = arith.cmpi sgt, %[[UB]], %[[C0]]
// NOEPILOGUE: scf.if
// NOEPILOGUE: %[[IF:.+]] = scf.if %[[CND0]]
// NOEPILOGUE: %[[A:.+]] = arith.addf
// NOEPILOGUE: scf.yield %[[A]]
// NOEPILOGUE: %[[S0:.+]] = arith.select %[[CND0]], %[[IF]], %[[CF]]
// NOEPILOGUE: scf.for %[[IV:.+]] = {{.*}} iter_args(%[[ARG:.+]] = %[[S0]],
// NOEPILOGUE: %[[UB_1:.+]] = arith.subi %[[UB]], %[[C1]] : index
// NOEPILOGUE: %[[CND1:.+]] = arith.cmpi slt, %[[IV]], %[[UB_1]] : index
// NOEPILOGUE: %[[S1:.+]] = arith.select %[[CND1]], %{{.+}}, %[[ARG]] : f32
// NOEPILOGUE: scf.yield %[[S1]]
%r = scf.for %i0 = %c0 to %ub step %c1 iter_args(%arg0 = %cf) -> (f32) {
%A_elem = memref.load %A[%i0] { __test_pipelining_stage__ = 0, __test_pipelining_op_order__ = 1 } : memref<?xf32>
%A1_elem = arith.addf %A_elem, %arg0 { __test_pipelining_stage__ = 1, __test_pipelining_op_order__ = 0 } : f32
memref.store %A1_elem, %result[%c0] { __test_pipelining_stage__ = 2, __test_pipelining_op_order__ = 2 } : memref<?xf32>
Expand Down
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