diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 0d3bd7edac0e..76baec7e6948 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -74,14 +74,14 @@ static FrontendAction *CreateFrontendBaseAction(CompilerInstance &CI) {
       if (it->getName() == CI.getFrontendOpts().ActionName) {
         std::unique_ptr<PluginASTAction> P(it->instantiate());
         if (!P->ParseArgs(CI, CI.getFrontendOpts().PluginArgs))
-          return 0;
+          return nullptr;
         return P.release();
       }
     }
 
     CI.getDiagnostics().Report(diag::err_fe_invalid_plugin_name)
       << CI.getFrontendOpts().ActionName;
-    return 0;
+    return nullptr;
   }
 
   case PrintDeclContext:       return new DeclContextPrintAction();
@@ -133,7 +133,7 @@ static FrontendAction *CreateFrontendAction(CompilerInstance &CI) {
   // Create the underlying action.
   FrontendAction *Act = CreateFrontendBaseAction(CI);
   if (!Act)
-    return 0;
+    return nullptr;
 
   const FrontendOptions &FEOpts = CI.getFrontendOpts();
 
@@ -217,7 +217,7 @@ bool clang::ExecuteCompilerInvocation(CompilerInstance *Clang) {
     Args[0] = "clang (LLVM option parsing)";
     for (unsigned i = 0; i != NumArgs; ++i)
       Args[i + 1] = Clang->getFrontendOpts().LLVMArgs[i].c_str();
-    Args[NumArgs + 1] = 0;
+    Args[NumArgs + 1] = nullptr;
     llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get());
   }
 
diff --git a/clang/lib/Index/CommentToXML.cpp b/clang/lib/Index/CommentToXML.cpp
index 891ce8109f9e..a67c806550d8 100644
--- a/clang/lib/Index/CommentToXML.cpp
+++ b/clang/lib/Index/CommentToXML.cpp
@@ -97,7 +97,7 @@ struct FullCommentParts {
 
 FullCommentParts::FullCommentParts(const FullComment *C,
                                    const CommandTraits &Traits) :
-    Brief(NULL), Headerfile(NULL), FirstParagraph(NULL) {
+    Brief(nullptr), Headerfile(nullptr), FirstParagraph(nullptr) {
   for (Comment::child_iterator I = C->child_begin(), E = C->child_end();
        I != E; ++I) {
     const Comment *Child = *I;
@@ -1150,7 +1150,7 @@ void CommentToXMLConverter::convertCommentToHTML(const FullComment *FC,
 void CommentToXMLConverter::convertHTMLTagNodeToText(
     const comments::HTMLTagComment *HTC, SmallVectorImpl<char> &Text,
     const ASTContext &Context) {
-  CommentASTToHTMLConverter Converter(0, Text,
+  CommentASTToHTMLConverter Converter(nullptr, Text,
                                       Context.getCommentCommandTraits());
   Converter.visit(HTC);
 }
diff --git a/clang/lib/Index/SimpleFormatContext.h b/clang/lib/Index/SimpleFormatContext.h
index 99d0d9a1cee0..147323a71051 100644
--- a/clang/lib/Index/SimpleFormatContext.h
+++ b/clang/lib/Index/SimpleFormatContext.h
@@ -52,7 +52,7 @@ public:
     const FileEntry *Entry =
         Files.getVirtualFile(Name, Source->getBufferSize(), 0);
     Sources.overrideFileContents(Entry, Source);
-    assert(Entry != NULL);
+    assert(Entry != nullptr);
     return Sources.createFileID(Entry, SourceLocation(), SrcMgr::C_User);
   }
 
diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
index 15aa87555e03..7554bc65b2ff 100644
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -109,7 +109,7 @@ public:
   bool ShouldGenerateLocation(const NamedDecl *D);
 
   bool isLocal(const NamedDecl *D) {
-    return D->getParentFunctionOrMethod() != 0;
+    return D->getParentFunctionOrMethod() != nullptr;
   }
 
   /// Generate the string component containing the location of the