It looks like the changes to the SRem logic of SimplifyDemandedUseBits
(fix for PR6165) are needed here too.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94801 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 91e5bc3..f9331e7 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -421,20 +421,29 @@
}
case Instruction::SRem:
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
- APInt RA = Rem->getValue();
- if (RA.isPowerOf2() || (-RA).isPowerOf2()) {
- APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA;
+ APInt RA = Rem->getValue().abs();
+ if (RA.isPowerOf2()) {
+ APInt LowBits = RA - 1;
APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
Depth+1);
- // If the sign bit of the first operand is zero, the sign bit of
- // the result is zero. If the first operand has no one bits below
- // the second operand's single 1 bit, its sign will be zero.
- if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits))
- KnownZero2 |= ~LowBits;
+ // The low bits of the first operand are unchanged by the srem.
+ KnownZero = KnownZero2 & LowBits;
+ KnownOne = KnownOne2 & LowBits;
- KnownZero |= KnownZero2 & Mask;
+ // If the first operand is non-negative or has all low bits zero, then
+ // the upper bits are all zero.
+ if (KnownZero2[BitWidth-1] || ((KnownZero2 & LowBits) == LowBits))
+ KnownZero |= ~LowBits;
+
+ // If the first operand is negative and not all low bits are zero, then
+ // the upper bits are all one.
+ if (KnownOne2[BitWidth-1] && ((KnownOne2 & LowBits) != 0))
+ KnownOne |= ~LowBits;
+
+ KnownZero &= Mask;
+ KnownOne &= Mask;
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
}