clean up some corner cases
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23692 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b58b8ca..efeee07 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1583,14 +1583,18 @@
SDOperand SrcValue = N->getOperand(3);
// If this is a store that kills a previous store, remove the previous store.
- if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr) {
+ if (Chain.getOpcode() == ISD::STORE && Chain.getOperand(2) == Ptr &&
+ Chain.Val->hasOneUse() /* Avoid introducing DAG cycles */) {
// Create a new store of Value that replaces both stores.
SDNode *PrevStore = Chain.Val;
+ if (PrevStore->getOperand(1) == Value) // Same value multiply stored.
+ return Chain;
SDOperand NewStore = DAG.getNode(ISD::STORE, MVT::Other,
PrevStore->getOperand(0), Value, Ptr,
SrcValue);
+ CombineTo(N, NewStore); // Nuke this store.
CombineTo(PrevStore, NewStore); // Nuke the previous store.
- return NewStore; // Replace this store with NewStore.
+ return SDOperand(N, 0);
}
return SDOperand();