+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?");
+
+ bool isKnownNegative = false;
+ bool isKnownNonNegative = false;
+ // If the multiplication is known not to overflow, compute the sign bit.
+ if (Mask.isNegative() &&
+ cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap()) {
+ Value *Op1 = I->getOperand(1), *Op2 = I->getOperand(0);
+ if (Op1 == Op2) {
+ // The product of a number with itself is non-negative.
+ isKnownNonNegative = true;
+ } else {
+ bool isKnownNonNegative1 = KnownZero.isNegative();
+ bool isKnownNonNegative2 = KnownZero2.isNegative();
+ bool isKnownNegative1 = KnownOne.isNegative();
+ bool isKnownNegative2 = KnownOne2.isNegative();
+ // The product of two numbers with the same sign is non-negative.
+ isKnownNonNegative = (isKnownNegative1 && isKnownNegative2) ||
+ (isKnownNonNegative1 && isKnownNonNegative2);
+ // The product of a negative number and a non-negative number is either
+ // negative or zero.
+ if (!isKnownNonNegative)
+ isKnownNegative = (isKnownNegative1 && isKnownNonNegative2 &&
+ isKnownNonZero(Op2, TD, Depth)) ||
+ (isKnownNegative2 && isKnownNonNegative1 &&
+ isKnownNonZero(Op1, TD, Depth));
+ }
+ }
+