Teach ValueTracking to look at the dividend when determining the sign bit of an
srem instruction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126637 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 1060bc5..fac0407 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -460,6 +460,18 @@
assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
}
}
+ if (Mask.isNegative()) { // We're looking for the sign bit.
+ APInt Mask2 = APInt::getSignBit(BitWidth);
+ KnownZero2 = 0;
+ KnownOne2 = 0;
+ ComputeMaskedBits(I->getOperand(0), Mask2, KnownZero2, KnownOne2, TD,
+ Depth+1);
+ if (KnownOne2[BitWidth-1])
+ KnownOne |= Mask2;
+ if (KnownZero2[BitWidth-1])
+ KnownZero |= Mask2;
+ assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?");
+ }
break;
case Instruction::URem: {
if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {