diff options
Diffstat (limited to 'lib/CodeGen')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 3 | ||||
| -rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 7 |
2 files changed, 9 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 2229743b92..e24a2942dd 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2119,6 +2119,9 @@ SDOperand DAGCombiner::visitXOR(SDNode *N) { if (FoldedVOp.Val) return FoldedVOp; } + // fold (xor undef, undef) -> 0. This is a common idiom (misuse). + if (N0.getOpcode() == ISD::UNDEF && N1.getOpcode() == ISD::UNDEF) + return DAG.getConstant(0, VT); // fold (xor x, undef) -> undef if (N0.getOpcode() == ISD::UNDEF) return N0; diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 05f7edb47c..ed564b2b7b 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -2245,6 +2245,12 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT, // Fold a bunch of operators when the RHS is undef. if (N2.getOpcode() == ISD::UNDEF) { switch (Opcode) { + case ISD::XOR: + if (N1.getOpcode() == ISD::UNDEF) + // Handle undef ^ undef -> 0 special case. This is a common + // idiom (misuse). + return getConstant(0, VT); + // fallthrough case ISD::ADD: case ISD::ADDC: case ISD::ADDE: @@ -2258,7 +2264,6 @@ SDOperand SelectionDAG::getNode(unsigned Opcode, MVT::ValueType VT, case ISD::SDIV: case ISD::UREM: case ISD::SREM: - case ISD::XOR: return N2; // fold op(arg1, undef) -> undef case ISD::MUL: case ISD::AND: |