// Compute the two solutions for the quadratic formula.
// The divisions must be performed as signed divisions.
APInt NegB(-B);
- APInt TwoA( A << 1 );
+ APInt TwoA(A << 1);
if (TwoA.isMinValue()) {
const SCEV *CNC = SE.getCouldNotCompute();
return std::make_pair(CNC, CNC);
return std::make_pair(SE.getConstant(Solution1),
SE.getConstant(Solution2));
- } // end APIntOps namespace
+ } // end APIntOps namespace
}
/// HowFarToZero - Return the number of times a backedge comparing the specified
// Handle unitary steps, which cannot wraparound.
// 1*N = -Start; -1*N = Start (mod 2^BW), so:
// N = Distance (as unsigned)
- if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue())
- return Distance;
+ if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
+ ConstantRange CR = getUnsignedRange(Start);
+ const SCEV *MaxBECount;
+ if (!CountDown && CR.getUnsignedMin().isMinValue())
+ // When counting up, the worst starting value is 1, not 0.
+ MaxBECount = CR.getUnsignedMax().isMinValue()
+ ? getConstant(APInt::getMinValue(CR.getBitWidth()))
+ : getConstant(APInt::getMaxValue(CR.getBitWidth()));
+ else
+ MaxBECount = getConstant(CountDown ? CR.getUnsignedMax()
+ : -CR.getUnsignedMin());
+ return ExitLimit(Distance, MaxBECount);
+ }
// If the recurrence is known not to wraparound, unsigned divide computes the
// back edge count. We know that the value will either become zero (and thus