diff options
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 7faf19fd72f..04ccc77b6bb 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -585,7 +585,7 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT, break; case ISD::ZERO_EXTEND: if (Operand.getValueType() == VT) return Operand; // noop extension - if (OpOpcode == ISD::ZERO_EXTEND) + if (OpOpcode == ISD::ZERO_EXTEND) // (zext (zext x)) -> (zext x) return getNode(ISD::ZERO_EXTEND, VT, Operand.Val->getOperand(0)); break; case ISD::TRUNCATE: @@ -1025,6 +1025,18 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT,SDOperand N1, return N1; } + // If we are extending the result of a setcc, and we already know the + // contents of the top bits, eliminate the extension. + if (N1.getOpcode() == ISD::SETCC) + switch (TLI.getSetCCResultContents()) { + case TargetLowering::UndefinedSetCCResult: break; + case TargetLowering::ZeroOrOneSetCCResult: + if (Opcode == ISD::ZERO_EXTEND_INREG) return N1; + break; + case TargetLowering::ZeroOrNegativeOneSetCCResult: + if (Opcode == ISD::SIGN_EXTEND_INREG) return N1; + break; + } break; } |
