diff options
Diffstat (limited to 'llvm/lib/CodeGen')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 30 |
1 files changed, 28 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 06123487f50..3b480377dfc 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -8902,6 +8902,7 @@ static SDValue tryToFoldExtendOfConstant(SDNode *N, const TargetLowering &TLI, unsigned Opcode = N->getOpcode(); SDValue N0 = N->getOperand(0); EVT VT = N->getValueType(0); + SDLoc DL(N); assert((Opcode == ISD::SIGN_EXTEND || Opcode == ISD::ZERO_EXTEND || Opcode == ISD::ANY_EXTEND || Opcode == ISD::SIGN_EXTEND_VECTOR_INREG || @@ -8912,7 +8913,33 @@ static SDValue tryToFoldExtendOfConstant(SDNode *N, const TargetLowering &TLI, // fold (zext c1) -> c1 // fold (aext c1) -> c1 if (isa<ConstantSDNode>(N0)) - return DAG.getNode(Opcode, SDLoc(N), VT, N0); + return DAG.getNode(Opcode, DL, VT, N0); + + // fold (sext (select cond, c1, c2)) -> (select cond, sext c1, sext c2) + // fold (zext (select cond, c1, c2)) -> (select cond, zext c1, zext c2) + // fold (aext (select cond, c1, c2)) -> (select cond, sext c1, sext c2) + if (N0->getOpcode() == ISD::SELECT) { + SDValue Op1 = N0->getOperand(1); + SDValue Op2 = N0->getOperand(2); + if (isa<ConstantSDNode>(Op1) && isa<ConstantSDNode>(Op2) && + (Opcode != ISD::ZERO_EXTEND || !TLI.isZExtFree(N0.getValueType(), VT))) { + // For any_extend, choose sign extension of the constants to allow a + // possible further transform to sign_extend_inreg.i.e. + // + // t1: i8 = select t0, Constant:i8<-1>, Constant:i8<0> + // t2: i64 = any_extend t1 + // --> + // t3: i64 = select t0, Constant:i64<-1>, Constant:i64<0> + // --> + // t4: i64 = sign_extend_inreg t3 + unsigned FoldOpc = Opcode; + if (FoldOpc == ISD::ANY_EXTEND) + FoldOpc = ISD::SIGN_EXTEND; + return DAG.getSelect(DL, VT, N0->getOperand(0), + DAG.getNode(FoldOpc, DL, VT, Op1), + DAG.getNode(FoldOpc, DL, VT, Op2)); + } + } // fold (sext (build_vector AllConstants) -> (build_vector AllConstants) // fold (zext (build_vector AllConstants) -> (build_vector AllConstants) @@ -8927,7 +8954,6 @@ static SDValue tryToFoldExtendOfConstant(SDNode *N, const TargetLowering &TLI, unsigned EVTBits = N0->getValueType(0).getScalarSizeInBits(); SmallVector<SDValue, 8> Elts; unsigned NumElts = VT.getVectorNumElements(); - SDLoc DL(N); // For zero-extensions, UNDEF elements still guarantee to have the upper // bits set to zero. |
