Revert "Move ExplodedNode reclaimation out of ExprEngine and into CoreEngine. Also have it based on adding predecessors/successors, not node allocation. No measurable performance change."

llvm-svn: 150722

clang/include/clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h

@@ -25,7 +25,6 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/DenseSet.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/GraphTraits.h"
@@ -241,7 +240,6 @@ public:
 class ExplodedGraph {
 protected:
   friend class CoreEngine;
-  friend class ExplodedNode;
 
   // Type definitions.
   typedef std::vector<ExplodedNode *> NodeVector;
@@ -267,7 +265,7 @@ protected:
   unsigned NumNodes;
   
   /// A list of recently allocated nodes that can potentially be recycled.
-  llvm::DenseSet<ExplodedNode*> ChangedNodes;
+  NodeVector ChangedNodes;
   
   /// A list of nodes that can be reused.
   NodeVector FreeNodes;
@@ -275,6 +273,9 @@ protected:
   /// A flag that indicates whether nodes should be recycled.
   bool reclaimNodes;
   
+  /// Counter to determine when to reclaim nodes.
+  unsigned reclaimCounter;
+
 public:
 
   /// \brief Retrieve the node associated with a (Location,State) pair,
@@ -360,12 +361,12 @@ public:
                     llvm::DenseMap<const void*, const void*> *InverseMap) const;
 
   /// Enable tracking of recently allocated nodes for potential reclamation
-  /// when calling reclaimChangedNodes().
+  /// when calling reclaimRecentlyAllocatedNodes().
   void enableNodeReclamation() { reclaimNodes = true; }
 
   /// Reclaim "uninteresting" nodes created since the last time this method
   /// was called.
-  void reclaimChangedNodes();
+  void reclaimRecentlyAllocatedNodes();
 
 private:
   bool shouldCollect(const ExplodedNode *node);

clang/lib/StaticAnalyzer/Core/CoreEngine.cpp

@@ -192,7 +192,6 @@ bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned Steps,
       --Steps;
     }
 
-    getGraph().reclaimChangedNodes();
     const WorkListUnit& WU = WList->dequeue();
 
     // Set the current block counter.

clang/lib/StaticAnalyzer/Core/ExplodedGraph.cpp

@@ -45,8 +45,10 @@ void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
 // Cleanup.
 //===----------------------------------------------------------------------===//
 
+static const unsigned CounterTop = 1000;
+
 ExplodedGraph::ExplodedGraph()
-  : NumNodes(0), reclaimNodes(false) {}
+  : NumNodes(0), reclaimNodes(false), reclaimCounter(CounterTop) {}
 
 ExplodedGraph::~ExplodedGraph() {}
 
@@ -125,12 +127,19 @@ void ExplodedGraph::collectNode(ExplodedNode *node) {
   node->~ExplodedNode();  
 }
 
-void ExplodedGraph::reclaimChangedNodes() {
+void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
   if (ChangedNodes.empty())
     return;
 
-  for (llvm::DenseSet<ExplodedNode*>::iterator it =
-       ChangedNodes.begin(), et = ChangedNodes.end();
+  // Only periodically relcaim nodes so that we can build up a set of
+  // nodes that meet the reclamation criteria.  Freshly created nodes
+  // by definition have no successor, and thus cannot be reclaimed (see below).
+  assert(reclaimCounter > 0);
+  if (--reclaimCounter != 0)
+    return;
+  reclaimCounter = CounterTop;
+
+  for (NodeVector::iterator it = ChangedNodes.begin(), et = ChangedNodes.end();
        it != et; ++it) {
     ExplodedNode *node = *it;
     if (shouldCollect(node))
@@ -151,12 +160,6 @@ void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) {
   assert (!V->isSink());
   Preds.addNode(V, G);
   V->Succs.addNode(this, G);
-  if (G.reclaimNodes) {
-    if (Succs.size() == 1 && Preds.size() == 1)
-      G.ChangedNodes.insert(this);
-    if (V->Succs.size() == 1 && V->Preds.size() == 1)
-      G.ChangedNodes.insert(V);
-  }  
 #ifndef NDEBUG
   if (NodeAuditor) NodeAuditor->AddEdge(V, this);
 #endif
@@ -253,6 +256,9 @@ ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
 
     new (V) NodeTy(L, State, IsSink);
 
+    if (reclaimNodes)
+      ChangedNodes.push_back(V);
+
     // Insert the node into the node set and return it.
     Nodes.InsertNode(V, InsertPos);
     ++NumNodes;

clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

@@ -239,6 +239,9 @@ static bool shouldRemoveDeadBindings(AnalysisManager &AMgr,
 
 void ExprEngine::ProcessStmt(const CFGStmt S,
                              ExplodedNode *Pred) {
+  // Reclaim any unnecessary nodes in the ExplodedGraph.
+  G.reclaimRecentlyAllocatedNodes();
+  
   currentStmt = S.getStmt();
   PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),
                                 currentStmt->getLocStart(),