[llvm] r221709 - Totally forget deallocated SDNodes in SDDbgInfo.

[Frederic Riss]

Author: friss
Date: Tue Nov 11 15:21:08 2014
New Revision: 221709

URL: http://llvm.org/viewvc/llvm-project?rev=221709&view=rev
Log:
Totally forget deallocated SDNodes in SDDbgInfo.

What would happen before that commit is that the SDDbgValues associated with
a deallocated SDNode would be marked Invalidated, but SDDbgInfo would keep
a map entry keyed by the SDNode pointer pointing to this list of invalidated
SDDbgNodes. As the memory gets reused, the list might get wrongly associated
with another new SDNode. As the SDDbgValues are cloned when they are transfered,
this can lead to an exponential number of SDDbgValues being produced during
DAGCombine like in http://llvm.org/bugs/show_bug.cgi?id=20893

Note that the previous behavior wasn't really buggy as the invalidation made
sure that the SDDbgValues won't be used. This commit can be considered a
memory optimization and as such is really hard to validate in a unit-test.

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

Modified: llvm/trunk/include/llvm/CodeGen/SelectionDAG.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/SelectionDAG.h?rev=221709&r1=221708&r2=221709&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/SelectionDAG.h (original)
+++ llvm/trunk/include/llvm/CodeGen/SelectionDAG.h Tue Nov 11 15:21:08 2014
@@ -128,6 +128,10 @@ public:
       DbgValMap[Node].push_back(V);
   }
 
+  /// \brief Invalidate all DbgValues attached to the node and remove
+  /// it from the Node-to-DbgValues map.
+  void erase(const SDNode *Node);
+
   void clear() {
     DbgValMap.clear();
     DbgValues.clear();

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=221709&r1=221708&r2=221709&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Tue Nov 11 15:21:08 2014
@@ -687,6 +687,15 @@ void SelectionDAG::DeleteNodeNotInCSEMap
   DeallocateNode(N);
 }
 
+void SDDbgInfo::erase(const SDNode *Node) {
+  DbgValMapType::iterator I = DbgValMap.find(Node);
+  if (I == DbgValMap.end())
+    return;
+  for (auto &Val: I->second)
+    Val->setIsInvalidated();
+  DbgValMap.erase(I);
+}
+
 void SelectionDAG::DeallocateNode(SDNode *N) {
   if (N->OperandsNeedDelete)
     delete[] N->OperandList;
@@ -697,10 +706,9 @@ void SelectionDAG::DeallocateNode(SDNode
 
   NodeAllocator.Deallocate(AllNodes.remove(N));
 
-  // If any of the SDDbgValue nodes refer to this SDNode, invalidate them.
-  ArrayRef<SDDbgValue*> DbgVals = DbgInfo->getSDDbgValues(N);
-  for (unsigned i = 0, e = DbgVals.size(); i != e; ++i)
-    DbgVals[i]->setIsInvalidated();
+  // If any of the SDDbgValue nodes refer to this SDNode, invalidate
+  // them and forget about that node.
+  DbgInfo->erase(N);
 }
 
 #ifndef NDEBUG