[llvm] r271733 - Re-apply "SDAG: Update ChainNodesMatched as nodes are deleted"

[Justin Bogner via llvm-commits]

Author: bogner
Date: Fri Jun  3 15:47:40 2016
New Revision: 271733

URL: http://llvm.org/viewvc/llvm-project?rev=271733&view=rev
Log:
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.

Modified:
    llvm/trunk/include/llvm/CodeGen/SelectionDAG.h
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAG.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAG.h?rev=271733&r1=271732&r2=271733&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SelectionDAG.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SelectionDAG.h Fri Jun  3 15:47:40 2016
@@ -249,6 +249,14 @@ public:
     virtual void NodeUpdated(SDNode *N);
   };
 
+  struct DAGNodeDeletedListener : public DAGUpdateListener {
+    std::function<void(SDNode *, SDNode *)> Callback;
+    DAGNodeDeletedListener(SelectionDAG &DAG,
+                           std::function<void(SDNode *, SDNode *)> Callback)
+        : DAGUpdateListener(DAG), Callback(Callback) {}
+    void NodeDeleted(SDNode *N, SDNode *E) override { Callback(N, E); }
+  };
+
   /// When true, additional steps are taken to
   /// ensure that getConstant() and similar functions return DAG nodes that
   /// have legal types. This is important after type legalization since

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp?rev=271733&r1=271732&r2=271733&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp Fri Jun  3 15:47:40 2016
@@ -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(
       } 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);
       }