Merging r167912: into the 3.2 release branch.

Handle DAG CSE adding new uses during ReplaceAllUsesWith. Fixes PR14333.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_32@168596 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 5416a5c1d7..37d7731aa1 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7728,7 +7728,18 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
       if (StoreNodes[i].MemNode == EarliestOp)
         continue;
       StoreSDNode *St = cast<StoreSDNode>(StoreNodes[i].MemNode);
-      DAG.ReplaceAllUsesOfValueWith(SDValue(St, 0), St->getChain());
+      // ReplaceAllUsesWith will replace all uses that existed when it was
+      // called, but graph optimizations may cause new ones to appear. For
+      // example, the case in pr14333 looks like
+      //
+      //  St's chain -> St -> another store -> X
+      //
+      // And the only difference from St to the other store is the chain.
+      // When we change it's chain to be St's chain they become identical,
+      // get CSEed and the net result is that X is now a use of St.
+      // Since we know that St is redundant, just iterate.
+      while (!St->use_empty())
+        DAG.ReplaceAllUsesWith(SDValue(St, 0), St->getChain());
       removeFromWorkList(St);
       DAG.DeleteNode(St);
     }