[analyzer] PCH deserialization optimization.

We should not deserialize unused declarations from the PCH file. Achieve
this by storing the top level declarations during parsing
(HandleTopLevelDecl ASTConsumer callback) and analyzing/building a call
graph only for those.

Tested the patch on a sample ObjC file that uses PCH. With the patch, 
 the analyzes is 17.5% faster and clang consumes 40% less memory.
Got about 10% overall build/analyzes time decrease on a large Objective
C project.

A bit of CallGraph refactoring/cleanup as well..

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154625 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 32 insertions, 61 deletions

diff --git a/lib/Analysis/CallGraph.cpp b/lib/Analysis/CallGraph.cpp
index 01d6c41f91..96a16c3afe 100644
--- a/lib/Analysis/CallGraph.cpp
+++ b/lib/Analysis/CallGraph.cpp
@@ -14,35 +14,12 @@
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
-#include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/StmtVisitor.h"
 
 #include "llvm/Support/GraphWriter.h"
 
 using namespace clang;
 
-/// Determine if a declaration should be included in the graph.
-static bool includeInGraph(const Decl *D) {
-  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
-    // We skip function template definitions, as their semantics is
-    // only determined when they are instantiated.
-    if (!FD->isThisDeclarationADefinition() ||
-        FD->isDependentContext())
-      return false;
-
-    IdentifierInfo *II = FD->getIdentifier();
-    if (II && II->getName().startswith("__inline"))
-      return false;
-  }
-
-  if (const ObjCMethodDecl *ID = dyn_cast<ObjCMethodDecl>(D)) {
-    if (!ID->isThisDeclarationADefinition())
-      return false;
-  }
-
-  return true;
-}
-
 namespace {
 /// A helper class, which walks the AST and locates all the call sites in the
 /// given function body.
@@ -60,8 +37,8 @@ public:
   void VisitCallExpr(CallExpr *CE) {
     // TODO: We need to handle ObjC method calls as well.
     if (FunctionDecl *CalleeDecl = CE->getDirectCallee())
-      if (includeInGraph(CalleeDecl)) {
-        CallGraphNode *CalleeNode = G->getOrInsertFunction(CalleeDecl);
+      if (G->includeInGraph(CalleeDecl)) {
+        CallGraphNode *CalleeNode = G->getOrInsertNode(CalleeDecl);
         CallerNode->addCallee(CalleeNode, G);
       }
   }
@@ -73,38 +50,10 @@ public:
   }
 };
 
-/// A helper class which walks the AST declarations.
-// TODO: We might want to specialize the visitor to shrink the call graph.
-// For example, we might not want to include the inline methods from header
-// files.
-class CGDeclVisitor : public RecursiveASTVisitor<CGDeclVisitor> {
-  CallGraph *CG;
-
-public:
-  CGDeclVisitor(CallGraph * InCG) : CG(InCG) {}
-
-  bool VisitFunctionDecl(FunctionDecl *FD) {
-    // We skip function template definitions, as their semantics is
-    // only determined when they are instantiated.
-    if (includeInGraph(FD))
-      // If this function has external linkage, anything could call it.
-      // Note, we are not precise here. For example, the function could have
-      // its address taken.
-      CG->addToCallGraph(FD, FD->isGlobal());
-    return true;
-  }
-
-  bool VisitObjCMethodDecl(ObjCMethodDecl *MD) {
-    if (includeInGraph(MD))
-      CG->addToCallGraph(MD, true);
-    return true;
-  }
-};
-
 } // end anonymous namespace
 
 CallGraph::CallGraph() {
-  Root = getOrInsertFunction(0);
+  Root = getOrInsertNode(0);
 }
 
 CallGraph::~CallGraph() {
@@ -116,10 +65,36 @@ CallGraph::~CallGraph() {
   }
 }
 
-void CallGraph::addToCallGraph(Decl* D, bool IsGlobal) {
+bool CallGraph::includeInGraph(const Decl *D) {
+  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    // We skip function template definitions, as their semantics is
+    // only determined when they are instantiated.
+    if (!FD->isThisDeclarationADefinition() ||
+        FD->isDependentContext())
+      return false;
+
+    IdentifierInfo *II = FD->getIdentifier();
+    if (II && II->getName().startswith("__inline"))
+      return false;
+  }
+
+  if (const ObjCMethodDecl *ID = dyn_cast<ObjCMethodDecl>(D)) {
+    if (!ID->isThisDeclarationADefinition())
+      return false;
+  }
+
+  return true;
+}
+
+void CallGraph::addNodeForDecl(Decl* D, bool IsGlobal) {
   assert(D);
-  CallGraphNode *Node = getOrInsertFunction(D);
 
+  // Do nothing if the node already exists.
+  if (FunctionMap.find(D) != FunctionMap.end())
+    return;
+
+  // Allocate a new node, mark it as root, and process it's calls.
+  CallGraphNode *Node = getOrInsertNode(D);
   if (IsGlobal)
     Root->addCallee(Node, this);
 
@@ -129,17 +104,13 @@ void CallGraph::addToCallGraph(Decl* D, bool IsGlobal) {
     builder.Visit(Body);
 }
 
-void CallGraph::addToCallGraph(TranslationUnitDecl *TU) {
-  CGDeclVisitor(this).TraverseDecl(TU);
-}
-
 CallGraphNode *CallGraph::getNode(const Decl *F) const {
   FunctionMapTy::const_iterator I = FunctionMap.find(F);
   if (I == FunctionMap.end()) return 0;
   return I->second;
 }
 
-CallGraphNode *CallGraph::getOrInsertFunction(Decl *F) {
+CallGraphNode *CallGraph::getOrInsertNode(Decl *F) {
   CallGraphNode *&Node = FunctionMap[F];
   if (Node)
     return Node;