Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/MC/MCLinkerOptimizationHint.h b/linux-x64/clang/include/llvm/MC/MCLinkerOptimizationHint.h
new file mode 100644
index 0000000..f0fd07f
--- /dev/null
+++ b/linux-x64/clang/include/llvm/MC/MCLinkerOptimizationHint.h
@@ -0,0 +1,187 @@
+//===- MCLinkerOptimizationHint.h - LOH interface ---------------*- C++ -*-===//
+//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares some helpers classes to handle Linker Optimization Hint
+// (LOH).
+//
+// FIXME: LOH interface supports only MachO format at the moment.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
+#define LLVM_MC_MCLINKEROPTIMIZATIONHINT_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+
+namespace llvm {
+
+class MachObjectWriter;
+class MCAsmLayout;
+class MCSymbol;
+
+/// Linker Optimization Hint Type.
+enum MCLOHType {
+  MCLOH_AdrpAdrp = 0x1u,      ///< Adrp xY, _v1@PAGE -> Adrp xY, _v2@PAGE.
+  MCLOH_AdrpLdr = 0x2u,       ///< Adrp _v@PAGE -> Ldr _v@PAGEOFF.
+  MCLOH_AdrpAddLdr = 0x3u,    ///< Adrp _v@PAGE -> Add _v@PAGEOFF -> Ldr.
+  MCLOH_AdrpLdrGotLdr = 0x4u, ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF -> Ldr.
+  MCLOH_AdrpAddStr = 0x5u,    ///< Adrp _v@PAGE -> Add _v@PAGEOFF -> Str.
+  MCLOH_AdrpLdrGotStr = 0x6u, ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF -> Str.
+  MCLOH_AdrpAdd = 0x7u,       ///< Adrp _v@PAGE -> Add _v@PAGEOFF.
+  MCLOH_AdrpLdrGot = 0x8u     ///< Adrp _v@GOTPAGE -> Ldr _v@GOTPAGEOFF.
+};
+
+static inline StringRef MCLOHDirectiveName() {
+  return StringRef(".loh");
+}
+
+static inline bool isValidMCLOHType(unsigned Kind) {
+  return Kind >= MCLOH_AdrpAdrp && Kind <= MCLOH_AdrpLdrGot;
+}
+
+static inline int MCLOHNameToId(StringRef Name) {
+#define MCLOHCaseNameToId(Name)     .Case(#Name, MCLOH_ ## Name)
+  return StringSwitch<int>(Name)
+    MCLOHCaseNameToId(AdrpAdrp)
+    MCLOHCaseNameToId(AdrpLdr)
+    MCLOHCaseNameToId(AdrpAddLdr)
+    MCLOHCaseNameToId(AdrpLdrGotLdr)
+    MCLOHCaseNameToId(AdrpAddStr)
+    MCLOHCaseNameToId(AdrpLdrGotStr)
+    MCLOHCaseNameToId(AdrpAdd)
+    MCLOHCaseNameToId(AdrpLdrGot)
+    .Default(-1);
+}
+
+static inline StringRef MCLOHIdToName(MCLOHType Kind) {
+#define MCLOHCaseIdToName(Name)      case MCLOH_ ## Name: return StringRef(#Name);
+  switch (Kind) {
+    MCLOHCaseIdToName(AdrpAdrp);
+    MCLOHCaseIdToName(AdrpLdr);
+    MCLOHCaseIdToName(AdrpAddLdr);
+    MCLOHCaseIdToName(AdrpLdrGotLdr);
+    MCLOHCaseIdToName(AdrpAddStr);
+    MCLOHCaseIdToName(AdrpLdrGotStr);
+    MCLOHCaseIdToName(AdrpAdd);
+    MCLOHCaseIdToName(AdrpLdrGot);
+  }
+  return StringRef();
+}
+
+static inline int MCLOHIdToNbArgs(MCLOHType Kind) {
+  switch (Kind) {
+    // LOH with two arguments
+  case MCLOH_AdrpAdrp:
+  case MCLOH_AdrpLdr:
+  case MCLOH_AdrpAdd:
+  case MCLOH_AdrpLdrGot:
+    return 2;
+    // LOH with three arguments
+  case MCLOH_AdrpAddLdr:
+  case MCLOH_AdrpLdrGotLdr:
+  case MCLOH_AdrpAddStr:
+  case MCLOH_AdrpLdrGotStr:
+    return 3;
+  }
+  return -1;
+}
+
+/// Store Linker Optimization Hint information (LOH).
+class MCLOHDirective {
+  MCLOHType Kind;
+
+  /// Arguments of this directive. Order matters.
+  SmallVector<MCSymbol *, 3> Args;
+
+  /// Emit this directive in \p OutStream using the information available
+  /// in the given \p ObjWriter and \p Layout to get the address of the
+  /// arguments within the object file.
+  void emit_impl(raw_ostream &OutStream, const MachObjectWriter &ObjWriter,
+                 const MCAsmLayout &Layout) const;
+
+public:
+  using LOHArgs = SmallVectorImpl<MCSymbol *>;
+
+  MCLOHDirective(MCLOHType Kind, const LOHArgs &Args)
+      : Kind(Kind), Args(Args.begin(), Args.end()) {
+    assert(isValidMCLOHType(Kind) && "Invalid LOH directive type!");
+  }
+
+  MCLOHType getKind() const { return Kind; }
+
+  const LOHArgs &getArgs() const { return Args; }
+
+  /// Emit this directive as:
+  /// <kind, numArgs, addr1, ..., addrN>
+  void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const;
+
+  /// Get the size in bytes of this directive if emitted in \p ObjWriter with
+  /// the given \p Layout.
+  uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
+                       const MCAsmLayout &Layout) const;
+};
+
+class MCLOHContainer {
+  /// Keep track of the emit size of all the LOHs.
+  mutable uint64_t EmitSize = 0;
+
+  /// Keep track of all LOH directives.
+  SmallVector<MCLOHDirective, 32> Directives;
+
+public:
+  using LOHDirectives = SmallVectorImpl<MCLOHDirective>;
+
+  MCLOHContainer() = default;
+
+  /// Const accessor to the directives.
+  const LOHDirectives &getDirectives() const {
+    return Directives;
+  }
+
+  /// Add the directive of the given kind \p Kind with the given arguments
+  /// \p Args to the container.
+  void addDirective(MCLOHType Kind, const MCLOHDirective::LOHArgs &Args) {
+    Directives.push_back(MCLOHDirective(Kind, Args));
+  }
+
+  /// Get the size of the directives if emitted.
+  uint64_t getEmitSize(const MachObjectWriter &ObjWriter,
+                       const MCAsmLayout &Layout) const {
+    if (!EmitSize) {
+      for (const MCLOHDirective &D : Directives)
+        EmitSize += D.getEmitSize(ObjWriter, Layout);
+    }
+    return EmitSize;
+  }
+
+  /// Emit all Linker Optimization Hint in one big table.
+  /// Each line of the table is emitted by LOHDirective::emit.
+  void emit(MachObjectWriter &ObjWriter, const MCAsmLayout &Layout) const {
+    for (const MCLOHDirective &D : Directives)
+      D.emit(ObjWriter, Layout);
+  }
+
+  void reset() {
+    Directives.clear();
+    EmitSize = 0;
+  }
+};
+
+// Add types for specialized template using MCSymbol.
+using MCLOHArgs = MCLOHDirective::LOHArgs;
+using MCLOHDirectives = MCLOHContainer::LOHDirectives;
+
+} // end namespace llvm
+
+#endif // LLVM_MC_MCLINKEROPTIMIZATIONHINT_H