diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index b9c560d1215..da63be3a1e1 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -23,9 +23,6 @@ // FIXME: mul (x, const) -> shifts + adds // FIXME: undef values // FIXME: make truncate see through SIGN_EXTEND and AND -// FIXME: (sra (sra x, c1), c2) -> (sra x, c1+c2) -// FIXME: verify that getNode can't return extends with an operand whose type -// is >= to that of the extend. // FIXME: divide by zero is currently left unfolded. do we want to turn this // into an undef? // FIXME: select ne (select cc, 1, 0), 0, true, false -> select cc, true, false @@ -1367,6 +1364,17 @@ SDOperand DAGCombiner::visitSRA(SDNode *N) { return DAG.getNode(ISD::SIGN_EXTEND_INREG, VT, N0.getOperand(0), DAG.getValueType(EVT)); } + + // fold (sra (sra x, c1), c2) -> (sra x, c1+c2) + if (N1C && N0.getOpcode() == ISD::SRA) { + if (ConstantSDNode *C1 = dyn_cast(N0.getOperand(1))) { + unsigned Sum = N1C->getValue() + C1->getValue(); + if (Sum >= MVT::getSizeInBits(VT)) Sum = MVT::getSizeInBits(VT)-1; + return DAG.getNode(ISD::SRA, VT, N0.getOperand(0), + DAG.getConstant(Sum, N1C->getValueType(0))); + } + } + // If the sign bit is known to be zero, switch this to a SRL. if (TLI.MaskedValueIsZero(N0, MVT::getIntVTSignBit(VT))) return DAG.getNode(ISD::SRL, VT, N0, N1);