diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index d5f3e9c..dda35f6 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -3748,6 +3748,26 @@ SDValue DAGCombiner::visitSHL(SDNode *N) { } } + // fold (shl (zext (srl x, C)), C) -> (zext (shl (srl x, C), C)) + // Only fold this if the inner zext has no other uses to avoid increasing + // the total number of instructions. + if (N1C && N0.getOpcode() == ISD::ZERO_EXTEND && N0.hasOneUse() && + N0.getOperand(0).getOpcode() == ISD::SRL && + isa<ConstantSDNode>(N0.getOperand(0)->getOperand(1))) { + uint64_t c1 = + cast<ConstantSDNode>(N0.getOperand(0)->getOperand(1))->getZExtValue(); + if (c1 < VT.getSizeInBits()) { + uint64_t c2 = N1C->getZExtValue(); + if (c1 == c2) { + SDValue NewOp0 = N0.getOperand(0); + EVT ShiftVT = NewOp0.getValueType(); + SDValue NewSHL = DAG.getNode(ISD::SHL, SDLoc(N), ShiftVT, + NewOp0, DAG.getConstant(c2, ShiftVT)); + return DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N0), VT, NewSHL); + } + } + } + // fold (shl (srl x, c1), c2) -> (and (shl x, (sub c2, c1), MASK) or // (and (srl x, (sub c1, c2), MASK) // Only fold this if the inner shift has no other uses -- if it does, folding |