Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/LTO/LTOBackend.h b/linux-x64/clang/include/llvm/LTO/LTOBackend.h
new file mode 100644
index 0000000..d4743f6
--- /dev/null
+++ b/linux-x64/clang/include/llvm/LTO/LTOBackend.h
@@ -0,0 +1,52 @@
+//===-LTOBackend.h - LLVM Link Time Optimizer Backend ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the "backend" phase of LTO, i.e. it performs
+// optimization and code generation on a loaded module. It is generally used
+// internally by the LTO class but can also be used independently, for example
+// to implement a standalone ThinLTO backend.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LTO_LTOBACKEND_H
+#define LLVM_LTO_LTOBACKEND_H
+
+#include "llvm/ADT/MapVector.h"
+#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/IR/ModuleSummaryIndex.h"
+#include "llvm/LTO/LTO.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Target/TargetOptions.h"
+#include "llvm/Transforms/IPO/FunctionImport.h"
+
+namespace llvm {
+
+class BitcodeModule;
+class Error;
+class Module;
+class Target;
+
+namespace lto {
+
+/// Runs a regular LTO backend. The regular LTO backend can also act as the
+/// regular LTO phase of ThinLTO, which may need to access the combined index.
+Error backend(Config &C, AddStreamFn AddStream,
+ unsigned ParallelCodeGenParallelismLevel,
+ std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
+
+/// Runs a ThinLTO backend.
+Error thinBackend(Config &C, unsigned Task, AddStreamFn AddStream, Module &M,
+ const ModuleSummaryIndex &CombinedIndex,
+ const FunctionImporter::ImportMapTy &ImportList,
+ const GVSummaryMapTy &DefinedGlobals,
+ MapVector<StringRef, BitcodeModule> &ModuleMap);
+}
+}
+
+#endif