diff options
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 3 |
1 files changed, 3 insertions, 0 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; |