building on the new CallGraphSCC abstraction, teach CallGraphSCCPassManager

to keep the node entries in scc_iterator up to date instead of dangling as
the SCC mutates.

This is a really terrible problem which was causing -g to affect codegen 
because it would permute the memory image of the compiler process.

Thanks to Dale for expertly hunting it down.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101565 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/SCCIterator.h

@@ -183,6 +183,15 @@ public:
         return true;
     return false;
   }
+                           
+  /// ReplaceNode - This informs the scc_iterator that the specified Old node
+  /// has been deleted, and New is to be used in its place.
+  void ReplaceNode(NodeType *Old, NodeType *New) {
+    assert(!nodeVisitNumbers.count(New) && "New already in scc_iterator?");
+    assert(nodeVisitNumbers.count(Old) && "Old not in scc_iterator?");
+    nodeVisitNumbers[New] = nodeVisitNumbers[Old];
+    nodeVisitNumbers.erase(Old);
+  }
 };
 
 

lib/Analysis/IPA/CallGraphSCCPass.cpp

@@ -417,6 +417,11 @@ void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
     Nodes[i] = New;
     break;
   }
+  
+  // Update the active scc_iterator so that it doesn't contain dangling
+  // pointers to the old CallGraphNode.
+  scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
+  CGI->ReplaceNode(Old, New);
 }