#endif
// Pick the smallest positive root value.
if (ConstantInt *CB =
- dyn_cast<ConstantInt>(ConstantExpr::getICmp(ICmpInst::ICMP_ULT,
- R1->getValue(), R2->getValue()))) {
+ dyn_cast<ConstantInt>(ConstantExpr::getICmp(CmpInst::ICMP_ULT,
+ R1->getValue(),
+ R2->getValue()))) {
if (CB->getZExtValue() == false)
std::swap(R1, R2); // R1 is the minimum root now.
const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
+ // If the AddRec is NUW, then (in an unsigned sense) it cannot be counting up
+ // to wrap to 0, it must be counting down to equal 0. Also, while counting
+ // down, it cannot "miss" 0 (which would cause it to wrap), regardless of what
+ // the stride is. As such, NUW addrec's will always become zero in
+ // "start / -stride" steps, and we know that the division is exact.
+ if (AddRec->hasNoUnsignedWrap())
+ return getUDivExpr(Start, getNegativeSCEV(Step));
+
// For now we handle only constant steps.
const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
if (StepC == 0)