diff options
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index cfaacd7..0c16bbc 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -4821,8 +4821,9 @@ ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) { #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. @@ -4856,6 +4857,14 @@ ScalarEvolution::HowFarToZero(const SCEV *V, const Loop *L) { 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) |