Re-apply "SDAG: Update ChainNodesMatched as nodes are deleted"

My first attempt at this had an overly aggressive assert - chain nodes
will only be removed, but we could hit the assert if a non-chain node
was CSE'd (NodeToMatch, for instance).

This reapplies r271706 by reverting r271713 and fixing an assert.

Original message:

Avoid relying on UB by looking into deleted nodes for a marker value.
Instead, update the list of chain nodes as we go.

llvm-svn: 271733

1 files changed, 9 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 359919e14b2..0ae1a95b875 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -2163,10 +2163,8 @@ void SelectionDAGISel::UpdateChains(
     // Replace all the chain results with the final chain we ended up with.
     for (unsigned i = 0, e = ChainNodesMatched.size(); i != e; ++i) {
       SDNode *ChainNode = ChainNodesMatched[i];
-
-      // If this node was already deleted, don't look at it.
-      if (ChainNode->getOpcode() == ISD::DELETED_NODE)
-        continue;
+      assert(ChainNode->getOpcode() != ISD::DELETED_NODE &&
+             "Deleted node left in chain");
 
       // Don't replace the results of the root node if we're doing a
       // MorphNodeTo.
@@ -3368,6 +3366,13 @@ void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
       } else {
         assert(NodeToMatch->getOpcode() != ISD::DELETED_NODE &&
                "NodeToMatch was removed partway through selection");
+        SelectionDAG::DAGNodeDeletedListener NDL(*CurDAG, [&](SDNode *N,
+                                                              SDNode *E) {
+          auto &Chain = ChainNodesMatched;
+          assert((!E || llvm::find(Chain, N) == Chain.end()) &&
+                 "Chain node replaced during MorphNode");
+          Chain.erase(std::remove(Chain.begin(), Chain.end(), N), Chain.end());
+        });
         Res = MorphNode(NodeToMatch, TargetOpc, VTList, Ops, EmitNodeInfo);
       }