[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..

llvm-svn: 154625

1 files changed, 20 insertions, 0 deletions

diff --git a/clang/test/Analysis/check-deserialization.cpp b/clang/test/Analysis/check-deserialization.cpp
new file mode 100644
index 00000000000..2b0bce2b9ad
--- /dev/null
+++ b/clang/test/Analysis/check-deserialization.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -emit-pch -o %t %s
+// RUN: %clang_cc1 -error-on-deserialized-decl S1_method -include-pch %t -analyze -analyzer-checker=core %s
+// RUN: %clang_cc1 -include-pch %t -analyze -analyzer-checker=core -verify %s
+
+#ifndef HEADER
+#define HEADER
+// Header.
+
+void S1_method(); // This should not be deserialized.
+
+
+#else
+// Using the header.
+
+int test() {
+  int x = 0;
+  return 5/x; //expected-warning {{Division by zero}}
+}
+
+#endif