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[mlir][SCF] Fix dynamic loop pipeline peeling for num_stages > total_iters #112418

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Merged
merged 2 commits into from
Oct 15, 2024
Merged

[mlir][SCF] Fix dynamic loop pipeline peeling for num_stages > total_iters #112418

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98e3147
[mlir][SCF] Fix dynamic loop pipeline peeling for num_stages > total_…
Oct 15, 2024
629e9de
* renamed getConst to createConst
Oct 15, 2024
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53 changes: 31 additions & 22 deletions mlir/lib/Dialect/SCF/Transforms/LoopPipelining.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -642,48 +642,57 @@ LogicalResult
LoopPipelinerInternal::emitEpilogue(RewriterBase &rewriter,
llvm::SmallVector<Value> &returnValues) {
Location loc = forOp.getLoc();
Type t = lb.getType();

// Emit different versions of the induction variable. They will be
// removed by dead code if not used.

// bounds_range = ub - lb
// total_iterations = (bounds_range + step - 1) / step
Type t = lb.getType();
Value zero =
rewriter.create<arith::ConstantOp>(loc, rewriter.getIntegerAttr(t, 0));
Value one =
rewriter.create<arith::ConstantOp>(loc, rewriter.getIntegerAttr(t, 1));
Value minusOne =
rewriter.create<arith::ConstantOp>(loc, rewriter.getIntegerAttr(t, -1));
auto getConst = [&](int v) {
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@ThomasRaoux ThomasRaoux Oct 15, 2024

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nit: maybe rename to createConst?

return rewriter.create<arith::ConstantOp>(loc,
rewriter.getIntegerAttr(t, v));
};

// total_iterations = cdiv(range_diff, step);
// - range_diff = ub - lb
// - total_iterations = (range_diff + step + (step < 0 ? 1 : -1)) / step
Value zero = getConst(0);
Value one = getConst(1);
Value stepLessZero = rewriter.create<arith::CmpIOp>(
loc, arith::CmpIPredicate::slt, step, zero);
Value stepDecr =
rewriter.create<arith::SelectOp>(loc, stepLessZero, one, minusOne);
rewriter.create<arith::SelectOp>(loc, stepLessZero, one, getConst(-1));

Value rangeDiff = rewriter.create<arith::SubIOp>(loc, ub, lb);
Value rangeIncrStep = rewriter.create<arith::AddIOp>(loc, rangeDiff, step);
Value rangeDecr =
rewriter.create<arith::AddIOp>(loc, rangeIncrStep, stepDecr);
Value totalIterations = rewriter.create<arith::DivSIOp>(loc, rangeDecr, step);

// If total_iters < max_stage, start the epilogue at zero to match the
// ramp-up in the prologue.
// start_iter = max(0, total_iters - max_stage)
Value iterI =
rewriter.create<arith::SubIOp>(loc, totalIterations, getConst(maxStage));
iterI = rewriter.create<arith::MaxSIOp>(loc, zero, iterI);

// Capture predicates for dynamic loops.
SmallVector<Value> predicates(maxStage + 1);
for (int64_t i = 0; i < maxStage; i++) {
// iterI = total_iters - 1 - i
// May go negative...
Value minusI =
rewriter.create<arith::ConstantOp>(loc, rewriter.getIntegerAttr(t, -i));
Value iterI = rewriter.create<arith::AddIOp>(
loc, rewriter.create<arith::AddIOp>(loc, totalIterations, minusOne),
minusI);

for (int64_t i = 1; i <= maxStage; i++) {
// newLastIter = lb + step * iterI
Value newlastIter = rewriter.create<arith::AddIOp>(
loc, lb, rewriter.create<arith::MulIOp>(loc, step, iterI));

setValueMapping(forOp.getInductionVar(), newlastIter, maxStage - i);
setValueMapping(forOp.getInductionVar(), newlastIter, i);

// increment to next iterI
iterI = rewriter.create<arith::AddIOp>(loc, iterI, one);

if (dynamicLoop) {
// pred = iterI >= 0
predicates[i + 1] = rewriter.create<arith::CmpIOp>(
loc, arith::CmpIPredicate::sge, iterI, zero);
// Disable stages when `i` is greater than total_iters.
// pred = total_iters >= i
predicates[i] = rewriter.create<arith::CmpIOp>(
loc, arith::CmpIPredicate::sge, totalIterations, getConst(i));
}
}

Expand Down
67 changes: 34 additions & 33 deletions mlir/test/Dialect/SCF/loop-pipelining.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -767,6 +767,7 @@ func.func @stage_0_value_escape(%A: memref<?xf32>, %result: memref<?xf32>, %ub:
// Check for predicated epilogue for dynamic loop.
// CHECK-LABEL: dynamic_loop(
// CHECK-DAG: %[[C1:.*]] = arith.constant 1 : index
// CHECK-DAG: %[[C2:.*]] = arith.constant 2 : index
// CHECK-DAG: %[[C0:.*]] = arith.constant 0 : index
// CHECK-DAG: %[[CM1:.*]] = arith.constant -1 : index
// CHECK: %[[UBM:.*]] = arith.subi %[[UB:.*]], %{{.*}}
Expand All @@ -779,32 +780,32 @@ func.func @stage_0_value_escape(%A: memref<?xf32>, %result: memref<?xf32>, %ub:
// CHECK: scf.yield %[[ADDF_24]], %[[LOAD_27]]
// CHECK: }
// CHECK: %[[CMPI_10:.*]] = arith.cmpi slt, %[[STEP]], %[[C0]]
// CHECK: %[[SEL_10:.*]] = arith.select %[[CMPI_10]], %[[C1]], %[[CM1]]
// CHECK: %[[SUBI_10:.*]] = arith.subi %[[UB]], %[[LB]]
// CHECK: %[[ADDI_11:.*]] = arith.addi %[[SUBI_10]], %[[STEP]]
// CHECK: %[[ADDI_12:.*]] = arith.addi %[[ADDI_11]], %[[SEL_10]]
// CHECK: %[[DIVSI_13:.*]] = arith.divsi %[[ADDI_12]], %[[STEP]]
// CHECK: %[[ADDI_14:.*]] = arith.addi %[[DIVSI_13]], %[[CM1]]
// CHECK: %[[MULI_15:.*]] = arith.muli %{{.*}}, %[[ADDI_14]]
// CHECK: %[[ADDI_16:.*]] = arith.addi %{{.*}}, %[[MULI_15]]
// CHECK: %[[CMPI_17:.*]] = arith.cmpi sge, %[[ADDI_14]], %[[C0]]
// CHECK: %[[ADDI_18:.*]] = arith.addi %[[DIVSI_13]], %{{.*}}-1
// CHECK: %[[ADDI_19:.*]] = arith.addi %[[ADDI_18]], %{{.*}}-1
// CHECK: %[[MULI_20:.*]] = arith.muli %{{.*}}, %[[ADDI_19]]
// CHECK: %[[ADDI_21:.*]] = arith.addi %{{.*}}, %[[MULI_20]]
// CHECK: %[[CMPI_22:.*]] = arith.cmpi sge, %[[ADDI_19]], %[[C0]]
// CHECK: scf.if %[[CMPI_17]] {
// CHECK: memref.store %{{.*}}#0, %{{.*}}[%[[ADDI_21]]]
// CHECK: %[[SELECT_11:.*]] = arith.select %[[CMPI_10]], %[[C1]], %[[CM1]]
// CHECK: %[[SUBI_12:.*]] = arith.subi %[[UB]], %[[LB]]
// CHECK: %[[ADDI_13:.*]] = arith.addi %[[SUBI_12]], %[[STEP]]
// CHECK: %[[ADDI_14:.*]] = arith.addi %[[ADDI_13]], %[[SELECT_11]]
// CHECK: %[[DIVSI_15:.*]] = arith.divsi %[[ADDI_14]], %[[STEP]]
// CHECK: %[[SUBI_17:.*]] = arith.subi %[[DIVSI_15]], %[[C2]]
// CHECK: %[[MAXSI_18:.*]] = arith.maxsi %[[SUBI_17]], %[[C0]]
// CHECK: %[[MULI_19:.*]] = arith.muli %[[STEP]], %[[MAXSI_18]]
// CHECK: %[[ADDI_20:.*]] = arith.addi %[[LB]], %[[MULI_19]]
// CHECK: %[[ADDI_21:.*]] = arith.addi %[[MAXSI_18]], %[[C1]]
// CHECK: %[[CMPI_22:.*]] = arith.cmpi sge, %[[DIVSI_15]], %[[C1]]
// CHECK: %[[MULI_23:.*]] = arith.muli %[[STEP]], %[[ADDI_21]]
// CHECK: %[[ADDI_24:.*]] = arith.addi %[[LB]], %[[MULI_23]]
// CHECK: %[[CMPI_25:.*]] = arith.cmpi sge, %[[DIVSI_15]], %[[C2]]
// CHECK: scf.if %[[CMPI_22]] {
// CHECK: memref.store %{{.*}}#0, %{{.*}}[%[[ADDI_20]]]
// CHECK: } else {
// CHECK: }
// CHECK: %[[IF_23:.*]] = scf.if %[[CMPI_22]] -> (f32) {
// CHECK: %[[ADDF_24:.*]] = arith.addf %{{.*}}#1, %{{.*}}
// CHECK: scf.yield %[[ADDF_24]]
// CHECK: %[[IF_26:.*]] = scf.if %[[CMPI_25]]
// CHECK: %[[ADDF_27:.*]] = arith.addf %{{.*}}#1, %{{.*}}
// CHECK: scf.yield %[[ADDF_27]]
// CHECK: } else {
// CHECK: scf.yield %{{.*}}
// CHECK: }
// CHECK: scf.if %[[CMPI_22]] {
// CHECK: memref.store %[[IF_23]], %{{.*}}[%[[ADDI_16]]]
// CHECK: scf.if %[[CMPI_25]] {
// CHECK: memref.store %[[IF_26]], %{{.*}}[%[[ADDI_24]]]
// CHECK: } else {
// CHECK: }
// CHECK: return
Expand Down Expand Up @@ -842,6 +843,7 @@ func.func @dynamic_loop(%A: memref<?xf32>, %result: memref<?xf32>, %lb: index, %
// CHECK-DAG: %[[C1:.*]] = arith.constant 1 : index
// CHECK-DAG: %[[C0:.*]] = arith.constant 0 : index
// CHECK-DAG: %[[CM1:.*]] = arith.constant -1 : index
// CHECK-DAG: %[[CF0:.*]] = arith.constant 0.000000e+00
// CHECK: %[[UBM:.*]] = arith.subi %[[UB:.*]], %{{.*}}
// CHECK: %{{.*}}:2 = scf.for %[[ARG5:.*]] = %[[LB:.*]] to %[[UBM]] step %[[STEP:.*]] iter_args(%[[ARG6:.*]] = %{{.*}}, %[[ARG7:.*]] = %{{.*}})
// CHECK: %[[ADDF_13:.*]] = arith.addf %[[ARG7]], %[[ARG6]]
Expand All @@ -856,22 +858,21 @@ func.func @dynamic_loop(%A: memref<?xf32>, %result: memref<?xf32>, %lb: index, %
// CHECK: %[[ADDI_7:.*]] = arith.addi %[[SUBI_6]], %[[STEP]]
// CHECK: %[[ADDI_8:.*]] = arith.addi %[[ADDI_7]], %[[SELECT_5]]
// CHECK: %[[DIVSI_9:.*]] = arith.divsi %[[ADDI_8]], %[[STEP]]
// CHECK: %[[ADDI_10:.*]] = arith.addi %[[DIVSI_9]], %[[CM1]]
// CHECK: %[[CMPI_11:.*]] = arith.cmpi sge, %[[ADDI_10]], %[[C0]]
// CHECK: %[[IF_10:.*]] = scf.if %[[CMPI_11]]
// CHECK: %[[ADDF_13:.*]] = arith.addf %{{.*}}#1, %{{.*}}#0
// CHECK: scf.yield %[[ADDF_13]]
// CHECK: %[[CMPI_10:.*]] = arith.cmpi sge, %[[DIVSI_9]], %[[C1]]
// CHECK: %[[IF_11:.*]] = scf.if %[[CMPI_10]]
// CHECK: %[[ADDF_14:.*]] = arith.addf %{{.*}}#1, %{{.*}}#0
// CHECK: scf.yield %[[ADDF_14]]
// CHECK: } else {
// CHECK: scf.yield %{{.*}}
// CHECK: scf.yield %[[CF0]]
// CHECK: }
// CHECK: %[[IF_11:.*]] = scf.if %[[CMPI_11]]
// CHECK: %[[MULF_13:.*]] = arith.mulf %[[IF_10]], %{{.*}}
// CHECK: scf.yield %[[MULF_13]]
// CHECK: %[[IF_12:.*]] = scf.if %[[CMPI_10]]
// CHECK: %[[MULF_14:.*]] = arith.mulf %[[IF_11]], %{{.*}}
// CHECK: scf.yield %[[MULF_14]]
// CHECK: } else {
// CHECK: scf.yield %{{.*}}
// CHECK: scf.yield %[[CF0]]
// CHECK: }
// CHECK: %[[SELECT_12:.*]] = arith.select %[[CMPI_11]], %[[IF_11]], %{{.*}}#0
// CHECK: memref.store %[[SELECT_12]], %{{.*}}[%{{.*}}]
// CHECK: %[[SELECT_13:.*]] = arith.select %[[CMPI_10]], %[[IF_12]], %{{.*}}#0
// CHECK: memref.store %[[SELECT_13]], %{{.*}}[%[[C0]]]
func.func @dynamic_loop_result(%A: memref<?xf32>, %result: memref<?xf32>, %lb: index, %ub: index, %step: index) {
%cf0 = arith.constant 1.0 : f32
%cf1 = arith.constant 33.0 : f32
Expand Down
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