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 5b1d103..69478e3 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -532,6 +532,10 @@ SDOperand DAGCombiner::visitSUB(SDNode *N) { ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0.Val); ConstantSDNode *N1C = dyn_cast<ConstantSDNode>(N1.Val); + // fold (sub x, x) -> 0 + if (N0 == N1) + return DAG.getConstant(0, N->getValueType(0)); + // fold (sub c1, c2) -> c1-c2 if (N0C && N1C) return DAG.getConstant(N0C->getValue() - N1C->getValue(), |