diff options
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
-rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index f346dcfcdd..98ae4db7ea 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -4592,6 +4592,56 @@ std::pair<SDValue, SDValue> SplitVSETCC(const SDNode *N, SelectionDAG &DAG) { return std::make_pair(Lo, Hi); } +// This function assumes all the vselect's arguments are CONCAT_VECTOR +// nodes and that the condition is a BV of ConstantSDNodes (or undefs). +static SDValue ConvertSelectToConcatVector(SDNode *N, SelectionDAG &DAG) { + SDLoc dl(N); + SDValue Cond = N->getOperand(0); + SDValue LHS = N->getOperand(1); + SDValue RHS = N->getOperand(2); + MVT VT = N->getSimpleValueType(0); + int NumElems = VT.getVectorNumElements(); + assert(LHS.getOpcode() == ISD::CONCAT_VECTORS && + RHS.getOpcode() == ISD::CONCAT_VECTORS && + Cond.getOpcode() == ISD::BUILD_VECTOR); + + // We're sure we have an even number of elements due to the + // concat_vectors we have as arguments to vselect. + // Skip BV elements until we find one that's not an UNDEF + // After we find an UNDEF element, keep looping until we get to half the + // length of the BV and see if all the non-undef nodes are the same. + ConstantSDNode *BottomHalf = nullptr; + for (int i = 0; i < NumElems / 2; ++i) { + if (Cond->getOperand(i)->getOpcode() == ISD::UNDEF) + continue; + + if (BottomHalf == nullptr) + BottomHalf = cast<ConstantSDNode>(Cond.getOperand(i)); + else if (Cond->getOperand(i).getNode() != BottomHalf) + return SDValue(); + } + + // Do the same for the second half of the BuildVector + ConstantSDNode *TopHalf = nullptr; + for (int i = NumElems / 2; i < NumElems; ++i) { + if (Cond->getOperand(i)->getOpcode() == ISD::UNDEF) + continue; + + if (TopHalf == nullptr) + TopHalf = cast<ConstantSDNode>(Cond.getOperand(i)); + else if (Cond->getOperand(i).getNode() != TopHalf) + return SDValue(); + } + + assert(TopHalf && BottomHalf && + "One half of the selector was all UNDEFs and the other was all the " + "same value. This should have been addressed before this function."); + return DAG.getNode( + ISD::CONCAT_VECTORS, dl, VT, + BottomHalf->isNullValue() ? RHS->getOperand(0) : LHS->getOperand(0), + TopHalf->isNullValue() ? RHS->getOperand(1) : LHS->getOperand(1)); +} + SDValue DAGCombiner::visitVSELECT(SDNode *N) { SDValue N0 = N->getOperand(0); SDValue N1 = N->getOperand(1); @@ -4664,6 +4714,17 @@ SDValue DAGCombiner::visitVSELECT(SDNode *N) { if (ISD::isBuildVectorAllZeros(N0.getNode())) return N2; + // The ConvertSelectToConcatVector function is assuming both the above + // checks for (vselect (build_vector all{ones,zeros) ...) have been made + // and addressed. + if (N1.getOpcode() == ISD::CONCAT_VECTORS && + N2.getOpcode() == ISD::CONCAT_VECTORS && + ISD::isBuildVectorOfConstantSDNodes(N0.getNode())) { + SDValue CV = ConvertSelectToConcatVector(N, DAG); + if (CV.getNode()) + return CV; + } + return SDValue(); } |