diff --git a/lib/Frontend/FrontendOptions.cpp b/lib/Frontend/FrontendOptions.cpp
new file mode 100644
index 0000000..bd91638
--- /dev/null
+++ b/lib/Frontend/FrontendOptions.cpp
@@ -0,0 +1,31 @@
+//===--- FrontendOptions.cpp ----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/FrontendOptions.h"
+#include "llvm/ADT/StringSwitch.h"
+using namespace clang;
+
+FrontendOptions::InputKind
+FrontendOptions::getInputKindForExtension(llvm::StringRef Extension) {
+  return llvm::StringSwitch<InputKind>(Extension)
+    .Case("ast", IK_AST)
+    .Case("c", IK_C)
+    .Cases("S", "s", IK_Asm)
+    .Case("i", IK_PreprocessedC)
+    .Case("ii", IK_PreprocessedCXX)
+    .Case("m", IK_ObjC)
+    .Case("mi", IK_PreprocessedObjC)
+    .Cases("mm", "M", IK_ObjCXX)
+    .Case("mii", IK_PreprocessedObjCXX)
+    .Case("C", IK_CXX)
+    .Cases("C", "cc", "cp", IK_CXX)
+    .Cases("cpp", "CPP", "c++", "cxx", "hpp", IK_CXX)
+    .Case("cl", IK_OpenCL)
+    .Default(IK_C);
+}