diff options
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index db4b392723..041c5007c5 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -4355,6 +4355,55 @@ SDValue DAGCombiner::visitBRCOND(SDNode *N) { N1.getOperand(0), N1.getOperand(1), N2); } + if (N1.hasOneUse() && N1.getOpcode() == ISD::SRL) { + // Match this pattern so that we can generate simpler code: + // + // %a = ... + // %b = and i32 %a, 2 + // %c = srl i32 %b, 1 + // brcond i32 %c ... + // + // into + // + // %a = ... + // %b = and %a, 2 + // %c = setcc eq %b, 0 + // brcond %c ... + // + // This applies only when the AND constant value has one bit set and the + // SRL constant is equal to the log2 of the AND constant. The back-end is + // smart enough to convert the result into a TEST/JMP sequence. + SDValue Op0 = N1.getOperand(0); + SDValue Op1 = N1.getOperand(1); + + if (Op0.getOpcode() == ISD::AND && + Op0.hasOneUse() && + Op1.getOpcode() == ISD::Constant) { + SDValue AndOp0 = Op0.getOperand(0); + SDValue AndOp1 = Op0.getOperand(1); + + if (AndOp1.getOpcode() == ISD::Constant) { + const APInt &AndConst = cast<ConstantSDNode>(AndOp1)->getAPIntValue(); + + if (AndConst.isPowerOf2() && + cast<ConstantSDNode>(Op1)->getAPIntValue()==AndConst.logBase2()) { + SDValue SetCC = + DAG.getSetCC(N->getDebugLoc(), + TLI.getSetCCResultType(Op0.getValueType()), + Op0, DAG.getConstant(0, Op0.getValueType()), + ISD::SETNE); + + // Replace the uses of SRL with SETCC + DAG.ReplaceAllUsesOfValueWith(N1, SetCC); + removeFromWorkList(N1.getNode()); + DAG.DeleteNode(N1.getNode()); + return DAG.getNode(ISD::BRCOND, N->getDebugLoc(), + MVT::Other, Chain, SetCC, N2); + } + } + } + } + return SDValue(); } |