- const SCEV *ShouldBeOne = SE.getMinusSCEV(CIVComparedToSCEV, LatchCount);
- const SCEVConstant *SCEVOne = dyn_cast<SCEVConstant>(ShouldBeOne);
- if (!SCEVOne || SCEVOne->getValue()->getValue() != 1) {
- FailureReason = "unexpected header count in latch";
- return false;
+ ConstantInt *One = ConstantInt::get(IndVarTy, 1);
+ // TODO: generalize the predicates here to also match their unsigned variants.
+ if (IsIncreasing) {
+ bool FoundExpectedPred =
+ (Pred == ICmpInst::ICMP_SLT && LatchBrExitIdx == 1) ||
+ (Pred == ICmpInst::ICMP_SGT && LatchBrExitIdx == 0);
+
+ if (!FoundExpectedPred) {
+ FailureReason = "expected icmp slt semantically, found something else";
+ return None;
+ }
+
+ if (LatchBrExitIdx == 0) {
+ if (CanBeSMax(SE, RightSCEV)) {
+ // TODO: this restriction is easily removable -- we just have to
+ // remember that the icmp was an slt and not an sle.
+ FailureReason = "limit may overflow when coercing sle to slt";
+ return None;
+ }
+
+ IRBuilder<> B(&*Preheader->rbegin());
+ RightValue = B.CreateAdd(RightValue, One);
+ }
+
+ } else {
+ bool FoundExpectedPred =
+ (Pred == ICmpInst::ICMP_SGT && LatchBrExitIdx == 1) ||
+ (Pred == ICmpInst::ICMP_SLT && LatchBrExitIdx == 0);
+
+ if (!FoundExpectedPred) {
+ FailureReason = "expected icmp sgt semantically, found something else";
+ return None;
+ }
+
+ if (LatchBrExitIdx == 0) {
+ if (CanBeSMin(SE, RightSCEV)) {
+ // TODO: this restriction is easily removable -- we just have to
+ // remember that the icmp was an sgt and not an sge.
+ FailureReason = "limit may overflow when coercing sge to sgt";
+ return None;
+ }
+
+ IRBuilder<> B(&*Preheader->rbegin());
+ RightValue = B.CreateSub(RightValue, One);
+ }