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[ConstraintElim] Use SCEV to check for multiples #76925

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Merged
merged 1 commit into from
Jan 4, 2024
Merged

[ConstraintElim] Use SCEV to check for multiples #76925

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21 changes: 4 additions & 17 deletions llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -968,23 +968,10 @@ void State::addInfoForInductions(BasicBlock &BB) {
return;

if (!StepOffset.isOne()) {
auto *UpperGEP = dyn_cast<GetElementPtrInst>(B);
if (!UpperGEP || UpperGEP->getPointerOperand() != StartValue ||
!UpperGEP->isInBounds())
return;

MapVector<Value *, APInt> UpperVariableOffsets;
APInt UpperConstantOffset(StepOffset.getBitWidth(), 0);
const DataLayout &DL = BB.getModule()->getDataLayout();
if (!UpperGEP->collectOffset(DL, StepOffset.getBitWidth(),
UpperVariableOffsets, UpperConstantOffset))
return;
// All variable offsets and the constant offset have to be a multiple of the
// step.
if (!UpperConstantOffset.urem(StepOffset).isZero() ||
any_of(UpperVariableOffsets, [&StepOffset](const auto &P) {
return !P.second.urem(StepOffset).isZero();
}))
// Check whether B-Start is known to be a multiple of StepOffset.
const SCEV *BMinusStart = SE.getMinusSCEV(SE.getSCEV(B), StartSCEV);
if (isa<SCEVCouldNotCompute>(BMinusStart) ||
!SE.getConstantMultiple(BMinusStart).urem(StepOffset).isZero())
return;
}

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15 changes: 5 additions & 10 deletions llvm/test/Transforms/ConstraintElimination/monotonic-int-phis-multiples.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -13,8 +13,7 @@ define void @multiple_pow2(i64 %count) {
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[EXIT:%.*]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[CMP2_I_I:%.*]] = icmp ult i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP2_I_I]], label [[LOOP]], label [[EXIT]]
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
Expand Down Expand Up @@ -48,8 +47,7 @@ define void @multiple_pow2_larger_than_needed(i64 %count) {
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[EXIT:%.*]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[CMP2_I_I:%.*]] = icmp ult i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP2_I_I]], label [[LOOP]], label [[EXIT]]
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
Expand Down Expand Up @@ -119,8 +117,7 @@ define void @multiple_pow2_start_offset(i64 %count) {
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[EXIT]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[CMP2_I_I:%.*]] = icmp ult i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP2_I_I]], label [[LOOP]], label [[EXIT]]
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
Expand Down Expand Up @@ -194,8 +191,7 @@ define void @multiple_pow2_start_offset_dynamic(i64 %count) {
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[EXIT]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[CMP2_I_I:%.*]] = icmp ult i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP2_I_I]], label [[LOOP]], label [[EXIT]]
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
Expand Down Expand Up @@ -231,8 +227,7 @@ define void @multiple_non_pow2_nuw(i64 %count) {
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[EXIT:%.*]], label [[LOOP_LATCH]]
; CHECK: loop.latch:
; CHECK-NEXT: [[CMP2_I_I:%.*]] = icmp ult i64 [[IV]], [[END]]
; CHECK-NEXT: br i1 [[CMP2_I_I]], label [[LOOP]], label [[EXIT]]
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
Expand Down