diff options
| -rw-r--r-- | lib/Target/X86/X86ISelLowering.cpp | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index bd95c85629..d64ac6ca22 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -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); } |