diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 6ac549b..dc59006 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2887,6 +2887,10 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) { if (SCC.Val) return SCC; } + // fold (sext x) -> (zext x) if the sign bit is known zero. + if (DAG.SignBitIsZero(N0)) + return DAG.getNode(ISD::ZERO_EXTEND, VT, N0); + return SDOperand(); } |