diff options
Diffstat (limited to 'lib/Target/X86/X86ISelLowering.cpp')
| -rw-r--r-- | lib/Target/X86/X86ISelLowering.cpp | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index 83c357d708..660a1bd0bd 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -8589,6 +8589,22 @@ SDValue X86TargetLowering::LowerSELECT(SDValue Op, SelectionDAG &DAG) const { SDValue Y = isAllOnes(Op2) ? Op1 : Op2; SDValue CmpOp0 = Cmp.getOperand(0); + // further optimization for special cases + // (select (x != 0), -1, 0) -> neg & sbb + // (select (x == 0), 0, -1) -> neg & sbb + if (ConstantSDNode *YC = dyn_cast<ConstantSDNode>(Y)) + if (YC->isNullValue() && + (isAllOnes(Op1) == (CondCode == X86::COND_NE))) { + SDVTList VTs = DAG.getVTList(CmpOp0.getValueType(), MVT::i32); + SDValue Neg = DAG.getNode(ISD::SUB, DL, VTs, + DAG.getConstant(0, CmpOp0.getValueType()), + CmpOp0); + SDValue Res = DAG.getNode(X86ISD::SETCC_CARRY, DL, Op.getValueType(), + DAG.getConstant(X86::COND_B, MVT::i8), + SDValue(Neg.getNode(), 1)); + return Res; + } + Cmp = DAG.getNode(X86ISD::CMP, DL, MVT::i32, CmpOp0, DAG.getConstant(1, CmpOp0.getValueType())); Cmp = ConvertCmpIfNecessary(Cmp, DAG); |