static analyzer: Further reduce the analyzer's memory usage when analyzing sqlite3 by 7-10% by recylcing "uninteresting" ExplodedNodes.

The optimization involves eagerly pruning ExplodedNodes from the ExplodedGraph that contain
practically no difference between the predecessor and successor nodes.  For example, if
the state is different between a predecessor and a node, the node is left in.  Only for
the 'environment' component of the state do we not care if the ExplodedNodes are different.
This paves the way for future optimizations where we can reclaim the environment objects.

llvm-svn: 125154

clang/include/clang/Driver/CC1Options.td

@@ -107,6 +107,8 @@ def analyzer_eagerly_assume : Flag<"-analyzer-eagerly-assume">,
   HelpText<"Eagerly assume the truth/falseness of some symbolic constraints">;
 def analyzer_no_purge_dead : Flag<"-analyzer-no-purge-dead">,
   HelpText<"Don't remove dead symbols, bindings, and constraints before processing a statement">;
+def analyzer_no_eagerly_trim_egraph : Flag<"-analyzer-no-eagerly-trim-egraph">,
+  HelpText<"Don't eagerly remove uninteresting ExplodedNodes from the ExplodedGraph">;
 def trim_egraph : Flag<"-trim-egraph">,
   HelpText<"Only show error-related paths in the analysis graph">;
 def analyzer_viz_egraph_graphviz : Flag<"-analyzer-viz-egraph-graphviz">,

clang/include/clang/Frontend/AnalyzerOptions.h

@@ -80,6 +80,7 @@ public:
   unsigned UnoptimizedCFG : 1;
   unsigned CFGAddImplicitDtors : 1;
   unsigned CFGAddInitializers : 1;
+  unsigned EagerlyTrimEGraph : 1;
 
 public:
   AnalyzerOptions() {
@@ -103,6 +104,7 @@ public:
     UnoptimizedCFG = 0;
     CFGAddImplicitDtors = 0;
     CFGAddInitializers = 0;
+    EagerlyTrimEGraph = 0;
   }
 };
 

clang/include/clang/StaticAnalyzer/PathSensitive/AnalysisManager.h

@@ -69,6 +69,7 @@ class AnalysisManager : public BugReporterData {
   bool EagerlyAssume;
   bool TrimGraph;
   bool InlineCall;
+  bool EagerlyTrimEGraph;
 
 public:
   AnalysisManager(ASTContext &ctx, Diagnostic &diags, 
@@ -79,14 +80,16 @@ public:
                   unsigned maxnodes, unsigned maxvisit,
                   bool vizdot, bool vizubi, bool purge, bool eager, bool trim,
                   bool inlinecall, bool useUnoptimizedCFG,
-                  bool addImplicitDtors, bool addInitializers)
+                  bool addImplicitDtors, bool addInitializers,
+                  bool eagerlyTrimEGraph)
 
     : AnaCtxMgr(useUnoptimizedCFG, addImplicitDtors, addInitializers),
       Ctx(ctx), Diags(diags), LangInfo(lang), PD(pd),
       CreateStoreMgr(storemgr), CreateConstraintMgr(constraintmgr),Idxer(idxer),
       AScope(ScopeDecl), MaxNodes(maxnodes), MaxVisit(maxvisit),
       VisualizeEGDot(vizdot), VisualizeEGUbi(vizubi), PurgeDead(purge),
-      EagerlyAssume(eager), TrimGraph(trim), InlineCall(inlinecall) {}
+      EagerlyAssume(eager), TrimGraph(trim), InlineCall(inlinecall),
+      EagerlyTrimEGraph(eagerlyTrimEGraph) {}
   
   ~AnalysisManager() { FlushDiagnostics(); }
   
@@ -146,6 +149,8 @@ public:
     return VisualizeEGDot || VisualizeEGUbi;
   }
 
+  bool shouldEagerlyTrimExplodedGraph() const { return EagerlyTrimEGraph; }
+
   bool shouldTrimGraph() const { return TrimGraph; }
 
   bool shouldPurgeDead() const { return PurgeDead; }

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

@@ -75,7 +75,7 @@ class ExplodedNode : public llvm::FoldingSetNode {
     ExplodedNode *getNode() const {
       return reinterpret_cast<ExplodedNode*>(getPtr());
     }
-
+    
   public:
     NodeGroup() : P(0) {}
 
@@ -89,6 +89,8 @@ class ExplodedNode : public llvm::FoldingSetNode {
 
     void addNode(ExplodedNode* N, ExplodedGraph &G);
 
+    void replaceNode(ExplodedNode *node);
+
     void setFlag() {
       assert(P == 0);
       P = AuxFlag;
@@ -208,6 +210,10 @@ public:
   };
 
   static void SetAuditor(Auditor* A);
+  
+private:
+  void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
+  void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
 };
 
 // FIXME: Is this class necessary?
@@ -249,6 +255,15 @@ protected:
 
   /// NumNodes - The number of nodes in the graph.
   unsigned NumNodes;
+  
+  /// A list of recently allocated nodes that can potentially be recycled.
+  void *recentlyAllocatedNodes;
+  
+  /// A list of nodes that can be reused.
+  void *freeNodes;
+  
+  /// A flag that indicates whether nodes should be recycled.
+  bool reclaimNodes;
 
 public:
   /// getNode - Retrieve the node associated with a (Location,State) pair,
@@ -275,10 +290,10 @@ public:
     return V;
   }
 
-  ExplodedGraph() : NumNodes(0) {}
+  ExplodedGraph() : NumNodes(0), recentlyAllocatedNodes(0), freeNodes(0) {}
-
-  ~ExplodedGraph() {}
 
+  ~ExplodedGraph();
+  
   unsigned num_roots() const { return Roots.size(); }
   unsigned num_eops() const { return EndNodes.size(); }
 
@@ -332,6 +347,14 @@ public:
                               const ExplodedNode* const * NEnd,
                               InterExplodedGraphMap *M,
                     llvm::DenseMap<const void*, const void*> *InverseMap) const;
+
+  /// Enable tracking of recently allocated nodes for potential reclamation
+  /// when calling reclaimRecentlyAllocatedNodes().
+  void enableNodeReclamation() { reclaimNodes = true; }
+
+  /// Reclaim "uninteresting" nodes created since the last time this method
+  /// was called.
+  void reclaimRecentlyAllocatedNodes();
 };
 
 class ExplodedNodeSet {

clang/include/clang/StaticAnalyzer/PathSensitive/GRState.h

@@ -78,6 +78,7 @@ private:
   void operator=(const GRState& R) const; // Do not implement.
 
   friend class GRStateManager;
+  friend class ExplodedGraph;
 
   llvm::PointerIntPair<GRStateManager *, 1, bool> stateMgr;
   Environment Env;           // Maps a Stmt to its current SVal.

clang/lib/Frontend/CompilerInvocation.cpp

@@ -878,6 +878,7 @@ static void ParseAnalyzerArgs(AnalyzerOptions &Opts, ArgList &Args,
   Opts.TrimGraph = Args.hasArg(OPT_trim_egraph);
   Opts.MaxNodes = Args.getLastArgIntValue(OPT_analyzer_max_nodes, 150000,Diags);
   Opts.MaxLoop = Args.getLastArgIntValue(OPT_analyzer_max_loop, 4, Diags);
+  Opts.EagerlyTrimEGraph = !Args.hasArg(OPT_analyzer_no_eagerly_trim_egraph);
   Opts.InlineCall = Args.hasArg(OPT_analyzer_inline_call);
   Opts.IdempotentOps = Args.hasArg(OPT_analysis_WarnIdempotentOps);
   Opts.ObjCSelfInitCheck = Args.hasArg(OPT_analysis_WarnObjCSelfInit);

clang/lib/StaticAnalyzer/Checkers/AnalysisConsumer.cpp

@@ -194,7 +194,8 @@ public:
                                   Opts.PurgeDead, Opts.EagerlyAssume,
                                   Opts.TrimGraph, Opts.InlineCall,
                                   Opts.UnoptimizedCFG, Opts.CFGAddImplicitDtors,
-                                  Opts.CFGAddInitializers));
+                                  Opts.CFGAddInitializers,
+                                  Opts.EagerlyTrimEGraph));
   }
 
   virtual void HandleTranslationUnit(ASTContext &C);

clang/lib/StaticAnalyzer/Checkers/ExprEngine.cpp

@@ -338,6 +338,11 @@ ExprEngine::ExprEngine(AnalysisManager &mgr, TransferFuncs *tf)
   // FIXME: Eventually remove the TF object entirely.
   TF->RegisterChecks(*this);
   TF->RegisterPrinters(getStateManager().Printers);
+  
+  if (mgr.shouldEagerlyTrimExplodedGraph()) {
+    // Enable eager node reclaimation when constructing the ExplodedGraph.  
+    G.enableNodeReclamation();
+  }
 }
 
 ExprEngine::~ExprEngine() {
@@ -573,6 +578,8 @@ void ExprEngine::processCFGElement(const CFGElement E,
 }
 
 void ExprEngine::ProcessStmt(const CFGStmt S, StmtNodeBuilder& builder) {
+  // Reclaim any unnecessary nodes in the ExplodedGraph.
+  G.reclaimRecentlyAllocatedNodes();
   // Recycle any unused states in the GRStateManager.
   StateMgr.recycleUnusedStates();
   

clang/lib/StaticAnalyzer/Core/CoreEngine.cpp

@@ -783,7 +783,8 @@ void CallEnterNodeBuilder::generateNode(const GRState *state) {
                          OldMgr.shouldInlineCall(),
                      OldMgr.getAnalysisContextManager().getUseUnoptimizedCFG(),
                      OldMgr.getAnalysisContextManager().getAddImplicitDtors(),
-                     OldMgr.getAnalysisContextManager().getAddInitializers());
+                     OldMgr.getAnalysisContextManager().getAddInitializers(),
+                     OldMgr.shouldEagerlyTrimExplodedGraph());
     llvm::OwningPtr<TransferFuncs> TF(MakeCFRefCountTF(AMgr.getASTContext(),
                                                          /* GCEnabled */ false,
                                                         AMgr.getLangOptions()));

clang/lib/StaticAnalyzer/Core/ExplodedGraph.cpp

@@ -40,6 +40,94 @@ void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
 #endif
 }
 
+//===----------------------------------------------------------------------===//
+// Cleanup.
+//===----------------------------------------------------------------------===//
+
+typedef std::vector<ExplodedNode*> NodeList;
+static inline NodeList*& getNodeList(void *&p) { return (NodeList*&) p; }
+
+ExplodedGraph::~ExplodedGraph() {
+  if (reclaimNodes) {
+    delete getNodeList(recentlyAllocatedNodes);
+    delete getNodeList(freeNodes);
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// Node reclamation.
+//===----------------------------------------------------------------------===//
+
+void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
+  if (!recentlyAllocatedNodes)
+    return;
+  NodeList &nl = *getNodeList(recentlyAllocatedNodes);
+ 
+  // Reclaimn all nodes that match *all* the following criteria:
+  //
+  // (1) 1 predecessor (that has one successor)
+  // (2) 1 successor (that has one predecessor)
+  // (3) The ProgramPoint is for a PostStmt.
+  // (4) There is no 'tag' for the ProgramPoint.
+  // (5) The 'store' is the same as the predecessor.
+  // (6) The 'GDM' is the same as the predecessor.
+  // (7) The LocationContext is the same as the predecessor.
+  // (8) The PostStmt is for a non-CFGElement expression.
+  
+  for (NodeList::iterator i = nl.begin(), e = nl.end() ; i != e; ++i) {
+    ExplodedNode *node = *i;
+    
+    // Conditions 1 and 2.
+    if (node->pred_size() != 1 || node->succ_size() != 1)
+      continue;
+
+    ExplodedNode *pred = *(node->pred_begin());
+    if (pred->succ_size() != 1)
+      continue;
+
+    ExplodedNode *succ = *(node->succ_begin());
+    if (succ->pred_size() != 1)
+      continue;
+
+    // Condition 3.
+    ProgramPoint progPoint = node->getLocation();
+    if (!isa<PostStmt>(progPoint))
+      continue;
+
+    // Condition 4.
+    PostStmt ps = cast<PostStmt>(progPoint);
+    if (ps.getTag() || isa<PostStmtCustom>(ps))
+      continue;
+
+    if (isa<BinaryOperator>(ps.getStmt()))
+      continue;
+
+    // Conditions 5, 6, and 7.
+    const GRState *state = node->getState();
+    const GRState *pred_state = pred->getState();    
+    if (state->St != pred_state->St || state->GDM != pred_state->GDM ||
+        progPoint.getLocationContext() != pred->getLocationContext())
+      continue;
+
+    // Condition 8.
+    if (node->getCFG().isBlkExpr(ps.getStmt()))
+      continue;
+    
+    // If we reach here, we can remove the node.  This means:
+    // (a) changing the predecessors successor to the successor of this node
+    // (b) changing the successors predecessor to the predecessor of this node
+    // (c) Putting 'node' onto freeNodes.
+    pred->replaceSuccessor(succ);
+    succ->replacePredecessor(pred);
+    if (!freeNodes)
+      freeNodes = new NodeList();
+    getNodeList(freeNodes)->push_back(node);
+    Nodes.RemoveNode(node);
+  }
+  
+  nl.clear();
+}
+
 //===----------------------------------------------------------------------===//
 // ExplodedNode.
 //===----------------------------------------------------------------------===//
@@ -57,6 +145,12 @@ void ExplodedNode::addPredecessor(ExplodedNode* V, ExplodedGraph &G) {
 #endif
 }
 
+void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) {
+  assert(getKind() == Size1);
+  P = reinterpret_cast<uintptr_t>(node);
+  assert(getKind() == Size1);
+}
+
 void ExplodedNode::NodeGroup::addNode(ExplodedNode* N, ExplodedGraph &G) {
   assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0);
   assert(!getFlag());
@@ -129,10 +223,24 @@ ExplodedNode *ExplodedGraph::getNode(const ProgramPoint& L,
   NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
 
   if (!V) {
-    // Allocate a new node.
+    if (freeNodes && !getNodeList(freeNodes)->empty()) {
-    V = (NodeTy*) getAllocator().Allocate<NodeTy>();
+      NodeList *nl = getNodeList(freeNodes);
+      V = nl->back();
+      nl->pop_back();
+    }
+    else {
+      // Allocate a new node.
+      V = (NodeTy*) getAllocator().Allocate<NodeTy>();
+    }
+
     new (V) NodeTy(L, State);
 
+    if (reclaimNodes) {
+      if (!recentlyAllocatedNodes)
+        recentlyAllocatedNodes = new NodeList();
+      getNodeList(recentlyAllocatedNodes)->push_back(V);
+    }
+
     // Insert the node into the node set and return it.
     Nodes.InsertNode(V, InsertPos);