diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 9d8850b59f5..656334b3dba 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -7616,6 +7616,32 @@ SDValue DAGCombiner::visitSRA(SDNode *N) { } } + // We convert trunc/ext to opposing shifts in IR, but casts may be cheaper. + // sra (add (shl X, N1C), AddC), N1C --> + // sext (add (trunc X to (width - N1C)), AddC') + if (!LegalOperations && N0.getOpcode() == ISD::ADD && N0.hasOneUse() && N1C && + N0.getOperand(0).getOpcode() == ISD::SHL && + N0.getOperand(0).getOperand(1) == N1 && N0.getOperand(0).hasOneUse()) { + if (ConstantSDNode *AddC = isConstOrConstSplat(N0.getOperand(1))) { + SDValue Shl = N0.getOperand(0); + // Determine what the truncate's type would be and ask the target if that + // is a free operation. + LLVMContext &Ctx = *DAG.getContext(); + unsigned ShiftAmt = N1C->getZExtValue(); + EVT TruncVT = EVT::getIntegerVT(Ctx, OpSizeInBits - ShiftAmt); + if (VT.isVector()) + TruncVT = EVT::getVectorVT(Ctx, TruncVT, VT.getVectorNumElements()); + if (TLI.isTruncateFree(VT, TruncVT)) { + SDLoc DL(N); + SDValue Trunc = DAG.getZExtOrTrunc(Shl.getOperand(0), DL, TruncVT); + SDValue ShiftC = DAG.getConstant(AddC->getAPIntValue().lshr(ShiftAmt). + trunc(TruncVT.getScalarSizeInBits()), DL, TruncVT); + SDValue Add = DAG.getNode(ISD::ADD, DL, TruncVT, Trunc, ShiftC); + return DAG.getSExtOrTrunc(Add, DL, VT); + } + } + } + // fold (sra x, (trunc (and y, c))) -> (sra x, (and (trunc y), (trunc c))). if (N1.getOpcode() == ISD::TRUNCATE && N1.getOperand(0).getOpcode() == ISD::AND) { |
