diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp
index 8f66d4c..16d2ea9 100644
--- a/lib/Frontend/ASTUnit.cpp
+++ b/lib/Frontend/ASTUnit.cpp
@@ -327,7 +327,13 @@
   CompilerInvocation CI;
   CompilerInvocation::CreateFromArgs(CI, (const char**) CCArgs.data(),
                                      (const char**) CCArgs.data()+CCArgs.size(),
-                                     Argv0, MainAddr, Diags);
+                                     Diags);
+
+  // Infer the builtin include path if unspecified.
+  if (CI.getHeaderSearchOpts().UseBuiltinIncludes &&
+      CI.getHeaderSearchOpts().BuiltinIncludePath.empty())
+    CI.getHeaderSearchOpts().BuiltinIncludePath =
+      CompilerInvocation::GetBuiltinIncludePath(Argv0, MainAddr);
 
   CI.getFrontendOpts().DisableFree = UseBumpAllocator;
   return LoadFromCompilerInvocation(CI, Diags, OnlyLocalDecls);
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 61995b4..102bbe2 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -951,8 +951,8 @@
   return DashX;
 }
 
-static std::string GetBuiltinIncludePath(const char *Argv0,
-                                         void *MainAddr) {
+std::string CompilerInvocation::GetBuiltinIncludePath(const char *Argv0,
+                                                      void *MainAddr) {
   llvm::sys::Path P = llvm::sys::Path::GetMainExecutable(Argv0, MainAddr);
 
   if (!P.isEmpty()) {
@@ -969,16 +969,16 @@
   return P.str();
 }
 
-static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args,
-                                  const char *Argv0, void *MainAddr) {
+static void ParseHeaderSearchArgs(HeaderSearchOptions &Opts, ArgList &Args) {
   using namespace cc1options;
   Opts.Sysroot = getLastArgValue(Args, OPT_isysroot, "/");
   Opts.Verbose = Args.hasArg(OPT_v);
+  Opts.UseBuiltinIncludes = !Args.hasArg(OPT_nobuiltininc);
   Opts.UseStandardIncludes = !Args.hasArg(OPT_nostdinc);
+  // Filled in by clients.
+  //
+  // FIXME: Elimate this.
   Opts.BuiltinIncludePath = "";
-  // FIXME: Add an option for this, its a slow call.
-  if (!Args.hasArg(OPT_nobuiltininc))
-    Opts.BuiltinIncludePath = GetBuiltinIncludePath(Argv0, MainAddr);
 
   // Add -I... and -F... options in order.
   for (arg_iterator it = Args.filtered_begin(OPT_I, OPT_F),
@@ -1262,8 +1262,6 @@
 void CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
                                         const char **ArgBegin,
                                         const char **ArgEnd,
-                                        const char *Argv0,
-                                        void *MainAddr,
                                         Diagnostic &Diags) {
   // Parse the arguments.
   llvm::OwningPtr<OptTable> Opts(createCC1OptTable());
@@ -1287,8 +1285,7 @@
   ParseDiagnosticArgs(Res.getDiagnosticOpts(), *Args, Diags);
   FrontendOptions::InputKind DashX =
     ParseFrontendArgs(Res.getFrontendOpts(), *Args, Diags);
-  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), *Args,
-                        Argv0, MainAddr);
+  ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), *Args);
   if (DashX != FrontendOptions::IK_AST)
     ParseLangArgs(Res.getLangOpts(), *Args, DashX, Diags);
   ParsePreprocessorArgs(Res.getPreprocessorOpts(), *Args, Diags);
diff --git a/lib/Frontend/InitHeaderSearch.cpp b/lib/Frontend/InitHeaderSearch.cpp
index 9825d0a..f5c9c74 100644
--- a/lib/Frontend/InitHeaderSearch.cpp
+++ b/lib/Frontend/InitHeaderSearch.cpp
@@ -730,7 +730,7 @@
   else
     Init.AddDelimitedPaths(HSOpts.CEnvIncPath);
 
-  if (!HSOpts.BuiltinIncludePath.empty()) {
+  if (HSOpts.UseBuiltinIncludes) {
     // Ignore the sys root, we *always* look for clang headers relative to
     // supplied path.
     Init.AddPath(HSOpts.BuiltinIncludePath, System,