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Recommit "[ConstraintElim] Simplify cmp after uadd.sat/usub.sat (#135603)" #136467

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Recommit "[ConstraintElim] Simplify cmp after uadd.sat/usub.sat (#135603)" #136467

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16 changes: 16 additions & 0 deletions llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1139,6 +1139,8 @@ void State::addInfoFor(BasicBlock &BB) {
// when simplifying uses of the min/max intrinsics.
[[fallthrough]];
case Intrinsic::abs:
case Intrinsic::uadd_sat:
case Intrinsic::usub_sat:
if (!isGuaranteedNotToBePoison(&I))
break;
WorkList.push_back(FactOrCheck::getInstFact(DT.getNode(&BB), &I));
Expand Down Expand Up @@ -1896,6 +1898,20 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT, LoopInfo &LI,
AddFact(Pred, MinMax, MinMax->getRHS());
continue;
}
if (auto *USatI = dyn_cast<SaturatingInst>(CB.Inst)) {
switch (USatI->getIntrinsicID()) {
default:
llvm_unreachable("Unexpected intrinsic.");
case Intrinsic::uadd_sat:
AddFact(ICmpInst::ICMP_UGE, USatI, USatI->getLHS());
AddFact(ICmpInst::ICMP_UGE, USatI, USatI->getRHS());
break;
case Intrinsic::usub_sat:
AddFact(ICmpInst::ICMP_ULE, USatI, USatI->getLHS());
break;
}
continue;
}
}

Value *A = nullptr, *B = nullptr;
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7 changes: 2 additions & 5 deletions llvm/test/Transforms/ConstraintElimination/uadd-usub-sat.ll
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Expand Up @@ -8,9 +8,7 @@ define i1 @uadd_sat_uge(i64 noundef %a, i64 noundef %b) {
; CHECK-LABEL: define i1 @uadd_sat_uge(
; CHECK-SAME: i64 noundef [[A:%.*]], i64 noundef [[B:%.*]]) {
; CHECK-NEXT: [[ADD_SAT:%.*]] = call i64 @llvm.uadd.sat.i64(i64 [[A]], i64 [[B]])
; CHECK-NEXT: [[CMP1:%.*]] = icmp uge i64 [[ADD_SAT]], [[A]]
; CHECK-NEXT: [[CMP2:%.*]] = icmp uge i64 [[ADD_SAT]], [[B]]
; CHECK-NEXT: [[CMP:%.*]] = and i1 [[CMP1]], [[CMP2]]
; CHECK-NEXT: [[CMP:%.*]] = and i1 true, true
; CHECK-NEXT: ret i1 [[CMP]]
;
%add.sat = call i64 @llvm.uadd.sat.i64(i64 %a, i64 %b)
Expand All @@ -24,8 +22,7 @@ define i1 @usub_sat_ule_lhs(i64 noundef %a, i64 noundef %b) {
; CHECK-LABEL: define i1 @usub_sat_ule_lhs(
; CHECK-SAME: i64 noundef [[A:%.*]], i64 noundef [[B:%.*]]) {
; CHECK-NEXT: [[SUB_SAT:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[A]], i64 [[B]])
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i64 [[SUB_SAT]], [[A]]
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 true
;
%sub.sat = call i64 @llvm.usub.sat.i64(i64 %a, i64 %b)
%cmp = icmp ule i64 %sub.sat, %a
Expand Down
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