diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/TargetLowering.cpp | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp index 6e6fedeb2e..389f2ea5ff 100644 --- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -1367,9 +1367,29 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op, } } - if (SimplifyDemandedBits(Op.getOperand(0), NewMask.lshr(ShAmt), + if (SimplifyDemandedBits(InOp, NewMask.lshr(ShAmt), KnownZero, KnownOne, TLO, Depth+1)) return true; + + // Convert (shl (anyext x, c)) to (anyext (shl x, c)) if the high bits + // are not demanded. This will likely allow the anyext to be folded away. + if (InOp.getNode()->getOpcode() == ISD::ANY_EXTEND) { + SDValue InnerOp = InOp.getNode()->getOperand(0); + EVT InnerVT = InnerOp.getValueType(); + if ((APInt::getHighBitsSet(BitWidth, + BitWidth - InnerVT.getSizeInBits()) & + DemandedMask) == 0 && + isTypeDesirableForOp(ISD::SHL, InnerVT)) { + SDValue NarrowShl = + TLO.DAG.getNode(ISD::SHL, dl, InnerVT, InnerOp, + TLO.DAG.getConstant(ShAmt, InnerVT)); + return + TLO.CombineTo(Op, + TLO.DAG.getNode(ISD::ANY_EXTEND, dl, Op.getValueType(), + NarrowShl)); + } + } + KnownZero <<= SA->getZExtValue(); KnownOne <<= SA->getZExtValue(); // low bits known zero. |