Introduce the 'Index' library.

Its purpose is to provide the basic infrastructure for cross-translation-unit analysis like indexing, refactoring, etc.

Currently it is very "primitive" and with no type-names support. It can provide functionality like
"show me all references of this function from these translation units".

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74802 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Index/Program.cpp b/lib/Index/Program.cpp
new file mode 100644
index 0000000..22fad9f
--- /dev/null
+++ b/lib/Index/Program.cpp
@@ -0,0 +1,48 @@
+//===--- Program.h - Entity originator and misc -----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  Storage for Entities and utility functions
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Index/Program.h"
+#include "ProgramImpl.h"
+#include "clang/Index/EntityHandler.h"
+#include "clang/Index/TranslationUnit.h"
+#include "clang/AST/DeclBase.h"
+#include "clang/AST/ASTContext.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace clang;
+using namespace idx;
+
+// Out-of-line to give the virtual tables a home.
+EntityHandler::~EntityHandler() { }
+TranslationUnit::~TranslationUnit() { }
+
+Program::Program() : Impl(new ProgramImpl()) { }
+
+Program::~Program() {
+  delete static_cast<ProgramImpl *>(Impl);
+}
+
+static void FindEntitiesInDC(DeclContext *DC, Program &Prog, EntityHandler *Handler) {
+  for (DeclContext::decl_iterator
+         I = DC->decls_begin(), E = DC->decls_end(); I != E; ++I) {
+    Entity *Ent = Entity::get(*I, Prog);
+    if (Ent)
+      Handler->HandleEntity(Ent);
+    if (DeclContext *SubDC = dyn_cast<DeclContext>(*I))
+      FindEntitiesInDC(SubDC, Prog, Handler);
+  }
+}
+
+/// \brief Traverses the AST and passes all the entities to the Handler.
+void Program::FindEntities(ASTContext &Ctx, EntityHandler *Handler) {
+  FindEntitiesInDC(Ctx.getTranslationUnitDecl(), *this, Handler);
+}