return XKnown.isNonZero() ||
isKnownNonZero(I->getOperand(0), DemandedElts, Depth, Q);
- return KnownBits::mul(XKnown, YKnown).isNonZero();
+ // If there exists any subset of X (sX) and subset of Y (sY) s.t sX * sY is
+ // non-zero, then X * Y is non-zero. We can find sX and sY by just taking
+ // the the lowest known One of X and Y. If they are non-zero, the result
+ // must be non-zero. We can check if LSB(X) * LSB(Y) != 0 by doing
+ // X.CountLeadingZeros + Y.CountLeadingZeros < BitWidth.
+ return (XKnown.countMaxTrailingZeros() + YKnown.countMaxTrailingZeros()) <
+ BitWidth;
}
case Instruction::Select:
// (C ? X : Y) != 0 if X != 0 and Y != 0.
define i1 @mul_nonzero_contains_nonzero_mul(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_nonzero_contains_nonzero_mul(
-; CHECK-NEXT: [[XX:%.*]] = or i8 [[X:%.*]], 16
-; CHECK-NEXT: [[YY:%.*]] = or i8 [[Y:%.*]], 8
-; CHECK-NEXT: [[XY:%.*]] = mul i8 [[XX]], [[YY]]
-; CHECK-NEXT: [[NZ:%.*]] = icmp ne i8 [[XY]], 0
-; CHECK-NEXT: ret i1 [[NZ]]
+; CHECK-NEXT: ret i1 true
;
%xx = or i8 %x, 16
%yy = or i8 %y, 8