diff --git a/include/llvm/MC/MCAsmInfo.h b/include/llvm/MC/MCAsmInfo.h
index f9486de..b8a0e02 100644
--- a/include/llvm/MC/MCAsmInfo.h
+++ b/include/llvm/MC/MCAsmInfo.h
@@ -117,6 +117,13 @@
     const char *InlineAsmStart;              // Defaults to "#APP\n"
     const char *InlineAsmEnd;                // Defaults to "#NO_APP\n"
 
+    /// Code16Directive, Code32Directive, Code64Directive - These are assembly
+    /// directives that tells the assembler to interpret the following
+    /// instructions differently.
+    const char *Code16Directive;             // Defaults to ".code16"
+    const char *Code32Directive;             // Defaults to ".code32"
+    const char *Code64Directive;             // Defaults to ".code64"
+
     /// AssemblerDialect - Which dialect of an assembler variant to use.
     unsigned AssemblerDialect;               // Defaults to 0
 
@@ -423,6 +430,15 @@
     const char *getInlineAsmEnd() const {
       return InlineAsmEnd;
     }
+    const char *getCode16Directive() const {
+      return Code16Directive;
+    }
+    const char *getCode32Directive() const {
+      return Code32Directive;
+    }
+    const char *getCode64Directive() const {
+      return Code64Directive;
+    }
     unsigned getAssemblerDialect() const {
       return AssemblerDialect;
     }
diff --git a/include/llvm/MC/MCAsmInfoDarwin.h b/include/llvm/MC/MCAsmInfoDarwin.h
index c85aa3d..1f6c499 100644
--- a/include/llvm/MC/MCAsmInfoDarwin.h
+++ b/include/llvm/MC/MCAsmInfoDarwin.h
@@ -18,11 +18,6 @@
 #include "llvm/MC/MCAsmInfo.h"
 
 namespace llvm {
-  class GlobalValue;
-  class GlobalVariable;
-  class Type;
-  class Mangler;
-
   struct MCAsmInfoDarwin : public MCAsmInfo {
     explicit MCAsmInfoDarwin();
   };
diff --git a/include/llvm/MC/MCDirectives.h b/include/llvm/MC/MCDirectives.h
index 1df55dc..9180d1b 100644
--- a/include/llvm/MC/MCDirectives.h
+++ b/include/llvm/MC/MCDirectives.h
@@ -47,8 +47,9 @@
 enum MCAssemblerFlag {
   MCAF_SyntaxUnified,         ///< .syntax (ARM/ELF)
   MCAF_SubsectionsViaSymbols, ///< .subsections_via_symbols (MachO)
-  MCAF_Code16,                ///< .code 16
-  MCAF_Code32                 ///< .code 32
+  MCAF_Code16,                ///< .code16 (X86) / .code 16 (ARM)
+  MCAF_Code32,                ///< .code32 (X86) / .code 32 (ARM)
+  MCAF_Code64                 ///< .code64 (X86)
 };
 
 } // end namespace llvm
diff --git a/lib/MC/MCAsmInfo.cpp b/lib/MC/MCAsmInfo.cpp
index 502b60b..015ccd4 100644
--- a/lib/MC/MCAsmInfo.cpp
+++ b/lib/MC/MCAsmInfo.cpp
@@ -42,6 +42,9 @@
   LinkerPrivateGlobalPrefix = "";
   InlineAsmStart = "APP";
   InlineAsmEnd = "NO_APP";
+  Code16Directive = ".code16";
+  Code32Directive = ".code32";
+  Code64Directive = ".code64";
   AssemblerDialect = 0;
   AllowQuotesInName = false;
   AllowNameToStartWithDigit = false;
diff --git a/lib/MC/MCAsmStreamer.cpp b/lib/MC/MCAsmStreamer.cpp
index c103ea6..40eaf97 100644
--- a/lib/MC/MCAsmStreamer.cpp
+++ b/lib/MC/MCAsmStreamer.cpp
@@ -335,8 +335,9 @@
   default: assert(0 && "Invalid flag!");
   case MCAF_SyntaxUnified:         OS << "\t.syntax unified"; break;
   case MCAF_SubsectionsViaSymbols: OS << ".subsections_via_symbols"; break;
-  case MCAF_Code16:                OS << "\t.code\t16"; break;
-  case MCAF_Code32:                OS << "\t.code\t32"; break;
+  case MCAF_Code16:                OS << '\t'<< MAI.getCode16Directive(); break;
+  case MCAF_Code32:                OS << '\t'<< MAI.getCode32Directive(); break;
+  case MCAF_Code64:                OS << '\t'<< MAI.getCode64Directive(); break;
   }
   EmitEOL();
 }
diff --git a/lib/MC/MCELFStreamer.cpp b/lib/MC/MCELFStreamer.cpp
index 84eab9d..573b3e4 100644
--- a/lib/MC/MCELFStreamer.cpp
+++ b/lib/MC/MCELFStreamer.cpp
@@ -53,8 +53,9 @@
 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
   switch (Flag) {
   case MCAF_SyntaxUnified: return; // no-op here.
-  case MCAF_Code16: return; // no-op here.
-  case MCAF_Code32: return; // no-op here.
+  case MCAF_Code16: return; // Change parsing mode; no-op here.
+  case MCAF_Code32: return; // Change parsing mode; no-op here.
+  case MCAF_Code64: return; // Change parsing mode; no-op here.
   case MCAF_SubsectionsViaSymbols:
     getAssembler().setSubsectionsViaSymbols(true);
     return;
diff --git a/lib/MC/MCMachOStreamer.cpp b/lib/MC/MCMachOStreamer.cpp
index 9312a49..844793b 100644
--- a/lib/MC/MCMachOStreamer.cpp
+++ b/lib/MC/MCMachOStreamer.cpp
@@ -143,8 +143,9 @@
   // Do any generic stuff we need to do.
   switch (Flag) {
   case MCAF_SyntaxUnified: return; // no-op here.
-  case MCAF_Code16: return; // no-op here.
-  case MCAF_Code32: return; // no-op here.
+  case MCAF_Code16: return; // Change parsing mode; no-op here.
+  case MCAF_Code32: return; // Change parsing mode; no-op here.
+  case MCAF_Code64: return; // Change parsing mode; no-op here.
   case MCAF_SubsectionsViaSymbols:
     getAssembler().setSubsectionsViaSymbols(true);
     return;
diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index 62c7dd0..eae1db0 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -1146,7 +1146,7 @@
     if (IDVal == ".include")
       return ParseDirectiveInclude();
 
-    if (IDVal == ".code16" || IDVal == ".code32" || IDVal == ".code64")
+    if (IDVal == ".code16")
       return TokError(Twine(IDVal) + " not supported yet");
 
     // Look up the handler in the handler table.
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 8eaf95a..b2c14a1 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -2702,13 +2702,15 @@
   Parser.Lex();
 
   if (Val == 16) {
-    if (!isThumb())
+    if (!isThumb()) {
       SwitchMode();
-    getParser().getStreamer().EmitAssemblerFlag(MCAF_Code16);
+      getParser().getStreamer().EmitAssemblerFlag(MCAF_Code16);
+    }
   } else {
-    if (isThumb())
+    if (isThumb()) {
       SwitchMode();
-    getParser().getStreamer().EmitAssemblerFlag(MCAF_Code32);
+      getParser().getStreamer().EmitAssemblerFlag(MCAF_Code32);
+    }
   }
 
   return false;
diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp
index 53b4c95..07e3540 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCAsmInfo.cpp
@@ -52,6 +52,9 @@
   AsmTransCBE = arm_asm_table;
   Data64bitsDirective = 0;
   CommentString = "@";
+  Code16Directive = ".code\t16";
+  Code32Directive = ".code\t32";
+
   SupportsDebugInformation = true;
 
   // Exceptions handling
@@ -64,12 +67,14 @@
 
   Data64bitsDirective = 0;
   CommentString = "@";
-
-  HasLEB128 = true;
   PrivateGlobalPrefix = ".L";
+  Code16Directive = ".code\t16";
+  Code32Directive = ".code\t32";
+
   WeakRefDirective = "\t.weak\t";
   HasLCOMMDirective = true;
 
+  HasLEB128 = true;
   SupportsDebugInformation = true;
 
   // Exceptions handling
diff --git a/lib/Target/X86/AsmParser/X86AsmParser.cpp b/lib/Target/X86/AsmParser/X86AsmParser.cpp
index 298f80a..e4adff6 100644
--- a/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -46,6 +46,7 @@
   X86Operand *ParseMemOperand(unsigned SegReg, SMLoc StartLoc);
 
   bool ParseDirectiveWord(unsigned Size, SMLoc L);
+  bool ParseDirectiveCode(StringRef IDVal, SMLoc L);
 
   bool MatchAndEmitInstruction(SMLoc IDLoc,
                                SmallVectorImpl<MCParsedAsmOperand*> &Operands,
@@ -63,6 +64,10 @@
     // FIXME: Can tablegen auto-generate this?
     return (STI.getFeatureBits() & X86::Mode64Bit) != 0;
   }
+  void SwitchMode() {
+    unsigned FB = ComputeAvailableFeatures(STI.ToggleFeature(X86::Mode64Bit));
+    setAvailableFeatures(FB);
+  }
 
   /// @name Auto-generated Matcher Functions
   /// {
@@ -1094,6 +1099,8 @@
   StringRef IDVal = DirectiveID.getIdentifier();
   if (IDVal == ".word")
     return ParseDirectiveWord(2, DirectiveID.getLoc());
+  else if (IDVal.startswith(".code"))
+    return ParseDirectiveCode(IDVal, DirectiveID.getLoc());
   return true;
 }
 
@@ -1122,7 +1129,27 @@
   return false;
 }
 
+/// ParseDirectiveCode
+///  ::= .code32 | .code64
+bool X86ATTAsmParser::ParseDirectiveCode(StringRef IDVal, SMLoc L) {
+  if (IDVal == ".code32") {
+    Parser.Lex();
+    if (is64BitMode()) {
+      SwitchMode();
+      getParser().getStreamer().EmitAssemblerFlag(MCAF_Code32);
+    }
+  } else if (IDVal == ".code64") {
+    Parser.Lex();
+    if (!is64BitMode()) {
+      SwitchMode();
+      getParser().getStreamer().EmitAssemblerFlag(MCAF_Code64);
+    }
+  } else {
+    return Error(L, "unexpected directive " + IDVal);
+  }
 
+  return false;
+}
 
 
 extern "C" void LLVMInitializeX86AsmLexer();