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Fix a bug in the code which determines when it's safe to use the

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bt instruction, which was exposed by r106263.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106718 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-06-24 02:07:59 +00:00
parent 37106afe02
commit 6b13cbca61
1 changed files with 13 additions and 7 deletions
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20
lib/Target/X86/X86ISelLowering.cpp
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@ -6175,15 +6175,21 @@ SDValue X86TargetLowering::LowerToBT(SDValue And, ISD::CondCode CC,
Op1 = Op1.getOperand(0);
SDValue LHS, RHS;
if (Op1.getOpcode() == ISD::SHL) {
if (ConstantSDNode *And10C = dyn_cast<ConstantSDNode>(Op1.getOperand(0)))
if (And10C->getZExtValue() == 1) {
LHS = Op0;
RHS = Op1.getOperand(1);
}
} else if (Op0.getOpcode() == ISD::SHL) {
if (Op1.getOpcode() == ISD::SHL)
std::swap(Op0, Op1);
if (Op0.getOpcode() == ISD::SHL) {
if (ConstantSDNode *And00C = dyn_cast<ConstantSDNode>(Op0.getOperand(0)))
if (And00C->getZExtValue() == 1) {
// If we looked past a truncate, check that it's only truncating away
// known zeros.
unsigned BitWidth = Op0.getValueSizeInBits();
unsigned AndBitWidth = And.getValueSizeInBits();
if (BitWidth > AndBitWidth) {
APInt Mask = APInt::getAllOnesValue(BitWidth), Zeros, Ones;
DAG.ComputeMaskedBits(Op0, Mask, Zeros, Ones);
if (Zeros.countLeadingOnes() < BitWidth - AndBitWidth)
return SDValue();
}
LHS = Op1;
RHS = Op0.getOperand(1);
}