diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 046c9e9520c..626dfaea957 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -236,6 +236,7 @@ namespace { SDValue visitSUB(SDNode *N); SDValue visitADDC(SDNode *N); SDValue visitSUBC(SDNode *N); + SDValue visitUSUBO(SDNode *N); SDValue visitADDE(SDNode *N); SDValue visitSUBE(SDNode *N); SDValue visitMUL(SDNode *N); @@ -1400,6 +1401,7 @@ SDValue DAGCombiner::visit(SDNode *N) { case ISD::SUB: return visitSUB(N); case ISD::ADDC: return visitADDC(N); case ISD::SUBC: return visitSUBC(N); + case ISD::USUBO: return visitUSUBO(N); case ISD::ADDE: return visitADDE(N); case ISD::SUBE: return visitSUBE(N); case ISD::MUL: return visitMUL(N); @@ -2133,6 +2135,38 @@ SDValue DAGCombiner::visitSUBC(SDNode *N) { return SDValue(); } +SDValue DAGCombiner::visitUSUBO(SDNode *N) { + SDValue N0 = N->getOperand(0); + SDValue N1 = N->getOperand(1); + EVT VT = N0.getValueType(); + if (VT.isVector()) + return SDValue(); + + EVT CarryVT = N->getValueType(1); + SDLoc DL(N); + + // If the flag result is dead, turn this into an SUB. + if (!N->hasAnyUseOfValue(1)) + return CombineTo(N, DAG.getNode(ISD::SUB, DL, VT, N0, N1), + DAG.getUNDEF(CarryVT)); + + // fold (usubo x, x) -> 0 + no borrow + if (N0 == N1) + return CombineTo(N, DAG.getConstant(0, DL, VT), + DAG.getConstant(0, DL, CarryVT)); + + // fold (usubo x, 0) -> x + no borrow + if (isNullConstant(N1)) + return CombineTo(N, N0, DAG.getConstant(0, DL, CarryVT)); + + // Canonicalize (usubo -1, x) -> ~x, i.e. (xor x, -1) + no borrow + if (isAllOnesConstant(N0)) + return CombineTo(N, DAG.getNode(ISD::XOR, DL, VT, N1, N0), + DAG.getConstant(0, DL, CarryVT)); + + return SDValue(); +} + SDValue DAGCombiner::visitSUBE(SDNode *N) { SDValue N0 = N->getOperand(0); SDValue N1 = N->getOperand(1); |
