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.

llvm-svn: 221709

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 7fb7aba00c4..4a83a3f00b5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -687,6 +687,15 @@ void SelectionDAG::DeleteNodeNotInCSEMaps(SDNode *N) {
   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 *N) {
 
   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