diff --git a/src/s390/disasm-s390.cc b/src/s390/disasm-s390.cc
new file mode 100644
index 0000000..5bab604
--- /dev/null
+++ b/src/s390/disasm-s390.cc
@@ -0,0 +1,1421 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// A Disassembler object is used to disassemble a block of code instruction by
+// instruction. The default implementation of the NameConverter object can be
+// overriden to modify register names or to do symbol lookup on addresses.
+//
+// The example below will disassemble a block of code and print it to stdout.
+//
+//   NameConverter converter;
+//   Disassembler d(converter);
+//   for (byte* pc = begin; pc < end;) {
+//     v8::internal::EmbeddedVector<char, 256> buffer;
+//     byte* prev_pc = pc;
+//     pc += d.InstructionDecode(buffer, pc);
+//     printf("%p    %08x      %s\n",
+//            prev_pc, *reinterpret_cast<int32_t*>(prev_pc), buffer);
+//   }
+//
+// The Disassembler class also has a convenience method to disassemble a block
+// of code into a FILE*, meaning that the above functionality could also be
+// achieved by just calling Disassembler::Disassemble(stdout, begin, end);
+
+#include <assert.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+
+#if V8_TARGET_ARCH_S390
+
+#include "src/base/platform/platform.h"
+#include "src/disasm.h"
+#include "src/macro-assembler.h"
+#include "src/s390/constants-s390.h"
+
+namespace v8 {
+namespace internal {
+
+//------------------------------------------------------------------------------
+
+// Decoder decodes and disassembles instructions into an output buffer.
+// It uses the converter to convert register names and call destinations into
+// more informative description.
+class Decoder {
+ public:
+  Decoder(const disasm::NameConverter& converter, Vector<char> out_buffer)
+      : converter_(converter), out_buffer_(out_buffer), out_buffer_pos_(0) {
+    out_buffer_[out_buffer_pos_] = '\0';
+  }
+
+  ~Decoder() {}
+
+  // Writes one disassembled instruction into 'buffer' (0-terminated).
+  // Returns the length of the disassembled machine instruction in bytes.
+  int InstructionDecode(byte* instruction);
+
+ private:
+  // Bottleneck functions to print into the out_buffer.
+  void PrintChar(const char ch);
+  void Print(const char* str);
+
+  // Printing of common values.
+  void PrintRegister(int reg);
+  void PrintDRegister(int reg);
+  void PrintSoftwareInterrupt(SoftwareInterruptCodes svc);
+
+  // Handle formatting of instructions and their options.
+  int FormatRegister(Instruction* instr, const char* option);
+  int FormatFloatingRegister(Instruction* instr, const char* option);
+  int FormatMask(Instruction* instr, const char* option);
+  int FormatDisplacement(Instruction* instr, const char* option);
+  int FormatImmediate(Instruction* instr, const char* option);
+  int FormatOption(Instruction* instr, const char* option);
+  void Format(Instruction* instr, const char* format);
+  void Unknown(Instruction* instr);
+  void UnknownFormat(Instruction* instr, const char* opcname);
+
+  bool DecodeTwoByte(Instruction* instr);
+  bool DecodeFourByte(Instruction* instr);
+  bool DecodeSixByte(Instruction* instr);
+
+  const disasm::NameConverter& converter_;
+  Vector<char> out_buffer_;
+  int out_buffer_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(Decoder);
+};
+
+// Support for assertions in the Decoder formatting functions.
+#define STRING_STARTS_WITH(string, compare_string) \
+  (strncmp(string, compare_string, strlen(compare_string)) == 0)
+
+// Append the ch to the output buffer.
+void Decoder::PrintChar(const char ch) { out_buffer_[out_buffer_pos_++] = ch; }
+
+// Append the str to the output buffer.
+void Decoder::Print(const char* str) {
+  char cur = *str++;
+  while (cur != '\0' && (out_buffer_pos_ < (out_buffer_.length() - 1))) {
+    PrintChar(cur);
+    cur = *str++;
+  }
+  out_buffer_[out_buffer_pos_] = 0;
+}
+
+// Print the register name according to the active name converter.
+void Decoder::PrintRegister(int reg) {
+  Print(converter_.NameOfCPURegister(reg));
+}
+
+// Print the double FP register name according to the active name converter.
+void Decoder::PrintDRegister(int reg) {
+  Print(DoubleRegister::from_code(reg).ToString());
+}
+
+// Print SoftwareInterrupt codes. Factoring this out reduces the complexity of
+// the FormatOption method.
+void Decoder::PrintSoftwareInterrupt(SoftwareInterruptCodes svc) {
+  switch (svc) {
+    case kCallRtRedirected:
+      Print("call rt redirected");
+      return;
+    case kBreakpoint:
+      Print("breakpoint");
+      return;
+    default:
+      if (svc >= kStopCode) {
+        out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d - 0x%x",
+                                    svc & kStopCodeMask, svc & kStopCodeMask);
+      } else {
+        out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", svc);
+      }
+      return;
+  }
+}
+
+// Handle all register based formatting in this function to reduce the
+// complexity of FormatOption.
+int Decoder::FormatRegister(Instruction* instr, const char* format) {
+  DCHECK(format[0] == 'r');
+
+  if (format[1] == '1') {  // 'r1: register resides in bit 8-11
+    RRInstruction* rrinstr = reinterpret_cast<RRInstruction*>(instr);
+    int reg = rrinstr->R1Value();
+    PrintRegister(reg);
+    return 2;
+  } else if (format[1] == '2') {  // 'r2: register resides in bit 12-15
+    RRInstruction* rrinstr = reinterpret_cast<RRInstruction*>(instr);
+    int reg = rrinstr->R2Value();
+    // indicating it is a r0 for displacement, in which case the offset
+    // should be 0.
+    if (format[2] == 'd') {
+      if (reg == 0) return 4;
+      PrintRegister(reg);
+      return 3;
+    } else {
+      PrintRegister(reg);
+      return 2;
+    }
+  } else if (format[1] == '3') {  // 'r3: register resides in bit 16-19
+    RSInstruction* rsinstr = reinterpret_cast<RSInstruction*>(instr);
+    int reg = rsinstr->B2Value();
+    PrintRegister(reg);
+    return 2;
+  } else if (format[1] == '4') {  // 'r4: register resides in bit 20-23
+    RSInstruction* rsinstr = reinterpret_cast<RSInstruction*>(instr);
+    int reg = rsinstr->B2Value();
+    PrintRegister(reg);
+    return 2;
+  } else if (format[1] == '5') {  // 'r5: register resides in bit 24-28
+    RREInstruction* rreinstr = reinterpret_cast<RREInstruction*>(instr);
+    int reg = rreinstr->R1Value();
+    PrintRegister(reg);
+    return 2;
+  } else if (format[1] == '6') {  // 'r6: register resides in bit 29-32
+    RREInstruction* rreinstr = reinterpret_cast<RREInstruction*>(instr);
+    int reg = rreinstr->R2Value();
+    PrintRegister(reg);
+    return 2;
+  } else if (format[1] == '7') {  // 'r6: register resides in bit 32-35
+    SSInstruction* ssinstr = reinterpret_cast<SSInstruction*>(instr);
+    int reg = ssinstr->B2Value();
+    PrintRegister(reg);
+    return 2;
+  }
+
+  UNREACHABLE();
+  return -1;
+}
+
+int Decoder::FormatFloatingRegister(Instruction* instr, const char* format) {
+  DCHECK(format[0] == 'f');
+
+  // reuse 1, 5 and 6 because it is coresponding
+  if (format[1] == '1') {  // 'r1: register resides in bit 8-11
+    RRInstruction* rrinstr = reinterpret_cast<RRInstruction*>(instr);
+    int reg = rrinstr->R1Value();
+    PrintDRegister(reg);
+    return 2;
+  } else if (format[1] == '2') {  // 'f2: register resides in bit 12-15
+    RRInstruction* rrinstr = reinterpret_cast<RRInstruction*>(instr);
+    int reg = rrinstr->R2Value();
+    PrintDRegister(reg);
+    return 2;
+  } else if (format[1] == '3') {  // 'f3: register resides in bit 16-19
+    RRDInstruction* rrdinstr = reinterpret_cast<RRDInstruction*>(instr);
+    int reg = rrdinstr->R1Value();
+    PrintDRegister(reg);
+    return 2;
+  } else if (format[1] == '5') {  // 'f5: register resides in bit 24-28
+    RREInstruction* rreinstr = reinterpret_cast<RREInstruction*>(instr);
+    int reg = rreinstr->R1Value();
+    PrintDRegister(reg);
+    return 2;
+  } else if (format[1] == '6') {  // 'f6: register resides in bit 29-32
+    RREInstruction* rreinstr = reinterpret_cast<RREInstruction*>(instr);
+    int reg = rreinstr->R2Value();
+    PrintDRegister(reg);
+    return 2;
+  }
+  UNREACHABLE();
+  return -1;
+}
+
+// FormatOption takes a formatting string and interprets it based on
+// the current instructions. The format string points to the first
+// character of the option string (the option escape has already been
+// consumed by the caller.)  FormatOption returns the number of
+// characters that were consumed from the formatting string.
+int Decoder::FormatOption(Instruction* instr, const char* format) {
+  switch (format[0]) {
+    case 'o': {
+      if (instr->Bit(10) == 1) {
+        Print("o");
+      }
+      return 1;
+    }
+    case '.': {
+      if (instr->Bit(0) == 1) {
+        Print(".");
+      } else {
+        Print(" ");  // ensure consistent spacing
+      }
+      return 1;
+    }
+    case 'r': {
+      return FormatRegister(instr, format);
+    }
+    case 'f': {
+      return FormatFloatingRegister(instr, format);
+    }
+    case 'i': {  // int16
+      return FormatImmediate(instr, format);
+    }
+    case 'u': {  // uint16
+      int32_t value = instr->Bits(15, 0);
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+      return 6;
+    }
+    case 'l': {
+      // Link (LK) Bit 0
+      if (instr->Bit(0) == 1) {
+        Print("l");
+      }
+      return 1;
+    }
+    case 'a': {
+      // Absolute Address Bit 1
+      if (instr->Bit(1) == 1) {
+        Print("a");
+      }
+      return 1;
+    }
+    case 't': {  // 'target: target of branch instructions
+      // target26 or target16
+      DCHECK(STRING_STARTS_WITH(format, "target"));
+      if ((format[6] == '2') && (format[7] == '6')) {
+        int off = ((instr->Bits(25, 2)) << 8) >> 6;
+        out_buffer_pos_ += SNPrintF(
+            out_buffer_ + out_buffer_pos_, "%+d -> %s", off,
+            converter_.NameOfAddress(reinterpret_cast<byte*>(instr) + off));
+        return 8;
+      } else if ((format[6] == '1') && (format[7] == '6')) {
+        int off = ((instr->Bits(15, 2)) << 18) >> 16;
+        out_buffer_pos_ += SNPrintF(
+            out_buffer_ + out_buffer_pos_, "%+d -> %s", off,
+            converter_.NameOfAddress(reinterpret_cast<byte*>(instr) + off));
+        return 8;
+      }
+      case 'm': {
+        return FormatMask(instr, format);
+      }
+    }
+    case 'd': {  // ds value for offset
+      return FormatDisplacement(instr, format);
+    }
+    default: {
+      UNREACHABLE();
+      break;
+    }
+  }
+
+  UNREACHABLE();
+  return -1;
+}
+
+int Decoder::FormatMask(Instruction* instr, const char* format) {
+  DCHECK(format[0] == 'm');
+  int32_t value = 0;
+  if ((format[1] == '1')) {  // prints the mask format in bits 8-12
+    value = reinterpret_cast<RRInstruction*>(instr)->R1Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "0x%x", value);
+    return 2;
+  } else if (format[1] == '2') {  // mask format in bits 16-19
+    value = reinterpret_cast<RXInstruction*>(instr)->B2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "0x%x", value);
+    return 2;
+  } else if (format[1] == '3') {  // mask format in bits 20-23
+    value = reinterpret_cast<RRFInstruction*>(instr)->M4Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "0x%x", value);
+    return 2;
+  }
+
+  out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+  return 2;
+}
+
+int Decoder::FormatDisplacement(Instruction* instr, const char* format) {
+  DCHECK(format[0] == 'd');
+
+  if (format[1] == '1') {  // displacement in 20-31
+    RSInstruction* rsinstr = reinterpret_cast<RSInstruction*>(instr);
+    uint16_t value = rsinstr->D2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+
+    return 2;
+  } else if (format[1] == '2') {  // displacement in 20-39
+    RXYInstruction* rxyinstr = reinterpret_cast<RXYInstruction*>(instr);
+    int32_t value = rxyinstr->D2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '4') {  // SS displacement 2 36-47
+    SSInstruction* ssInstr = reinterpret_cast<SSInstruction*>(instr);
+    uint16_t value = ssInstr->D2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '3') {  // SS displacement 1 20 - 32
+    SSInstruction* ssInstr = reinterpret_cast<SSInstruction*>(instr);
+    uint16_t value = ssInstr->D1Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else {  // s390 specific
+    int32_t value = SIGN_EXT_IMM16(instr->Bits(15, 0) & ~3);
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 1;
+  }
+}
+
+int Decoder::FormatImmediate(Instruction* instr, const char* format) {
+  DCHECK(format[0] == 'i');
+
+  if (format[1] == '1') {  // immediate in 16-31
+    RIInstruction* riinstr = reinterpret_cast<RIInstruction*>(instr);
+    int16_t value = riinstr->I2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '2') {  // immediate in 16-48
+    RILInstruction* rilinstr = reinterpret_cast<RILInstruction*>(instr);
+    int32_t value = rilinstr->I2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '3') {  // immediate in I format
+    IInstruction* iinstr = reinterpret_cast<IInstruction*>(instr);
+    int8_t value = iinstr->IValue();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '4') {  // immediate in 16-31, but outputs as offset
+    RIInstruction* riinstr = reinterpret_cast<RIInstruction*>(instr);
+    int16_t value = riinstr->I2Value() * 2;
+    if (value >= 0)
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*+");
+    else
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*");
+
+    out_buffer_pos_ += SNPrintF(
+        out_buffer_ + out_buffer_pos_, "%d -> %s", value,
+        converter_.NameOfAddress(reinterpret_cast<byte*>(instr) + value));
+    return 2;
+  } else if (format[1] == '5') {  // immediate in 16-31, but outputs as offset
+    RILInstruction* rilinstr = reinterpret_cast<RILInstruction*>(instr);
+    int32_t value = rilinstr->I2Value() * 2;
+    if (value >= 0)
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*+");
+    else
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*");
+
+    out_buffer_pos_ += SNPrintF(
+        out_buffer_ + out_buffer_pos_, "%d -> %s", value,
+        converter_.NameOfAddress(reinterpret_cast<byte*>(instr) + value));
+    return 2;
+  } else if (format[1] == '6') {  // unsigned immediate in 16-31
+    RIInstruction* riinstr = reinterpret_cast<RIInstruction*>(instr);
+    uint16_t value = riinstr->I2UnsignedValue();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '7') {  // unsigned immediate in 16-47
+    RILInstruction* rilinstr = reinterpret_cast<RILInstruction*>(instr);
+    uint32_t value = rilinstr->I2UnsignedValue();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '8') {  // unsigned immediate in 8-15
+    SSInstruction* ssinstr = reinterpret_cast<SSInstruction*>(instr);
+    uint8_t value = ssinstr->Length();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == '9') {  // unsigned immediate in 16-23
+    RIEInstruction* rie_instr = reinterpret_cast<RIEInstruction*>(instr);
+    uint8_t value = rie_instr->I3Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == 'a') {  // unsigned immediate in 24-31
+    RIEInstruction* rie_instr = reinterpret_cast<RIEInstruction*>(instr);
+    uint8_t value = rie_instr->I4Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == 'b') {  // unsigned immediate in 32-39
+    RIEInstruction* rie_instr = reinterpret_cast<RIEInstruction*>(instr);
+    uint8_t value = rie_instr->I5Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == 'c') {  // signed immediate in 8-15
+    SSInstruction* ssinstr = reinterpret_cast<SSInstruction*>(instr);
+    int8_t value = ssinstr->Length();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == 'd') {  // signed immediate in 32-47
+    SILInstruction* silinstr = reinterpret_cast<SILInstruction*>(instr);
+    int16_t value = silinstr->I2Value();
+    out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%d", value);
+    return 2;
+  } else if (format[1] == 'e') {  // immediate in 16-47, but outputs as offset
+    RILInstruction* rilinstr = reinterpret_cast<RILInstruction*>(instr);
+    int32_t value = rilinstr->I2Value() * 2;
+    if (value >= 0)
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*+");
+    else
+      out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "*");
+
+    out_buffer_pos_ += SNPrintF(
+        out_buffer_ + out_buffer_pos_, "%d -> %s", value,
+        converter_.NameOfAddress(reinterpret_cast<byte*>(instr) + value));
+    return 2;
+  }
+
+  UNREACHABLE();
+  return -1;
+}
+
+// Format takes a formatting string for a whole instruction and prints it into
+// the output buffer. All escaped options are handed to FormatOption to be
+// parsed further.
+void Decoder::Format(Instruction* instr, const char* format) {
+  char cur = *format++;
+  while ((cur != 0) && (out_buffer_pos_ < (out_buffer_.length() - 1))) {
+    if (cur == '\'') {  // Single quote is used as the formatting escape.
+      format += FormatOption(instr, format);
+    } else {
+      out_buffer_[out_buffer_pos_++] = cur;
+    }
+    cur = *format++;
+  }
+  out_buffer_[out_buffer_pos_] = '\0';
+}
+
+// The disassembler may end up decoding data inlined in the code. We do not want
+// it to crash if the data does not ressemble any known instruction.
+#define VERIFY(condition) \
+  if (!(condition)) {     \
+    Unknown(instr);       \
+    return;               \
+  }
+
+// For currently unimplemented decodings the disassembler calls Unknown(instr)
+// which will just print "unknown" of the instruction bits.
+void Decoder::Unknown(Instruction* instr) { Format(instr, "unknown"); }
+
+// For currently unimplemented decodings the disassembler calls
+// UnknownFormat(instr) which will just print opcode name of the
+// instruction bits.
+void Decoder::UnknownFormat(Instruction* instr, const char* name) {
+  char buffer[100];
+  snprintf(buffer, sizeof(buffer), "%s (unknown-format)", name);
+  Format(instr, buffer);
+}
+
+// Disassembles Two Byte S390 Instructions
+// @return true if successfully decoded
+bool Decoder::DecodeTwoByte(Instruction* instr) {
+  // Print the Instruction bits.
+  out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%04x           ",
+                              instr->InstructionBits<TwoByteInstr>());
+
+  Opcode opcode = instr->S390OpcodeValue();
+  switch (opcode) {
+    case AR:
+      Format(instr, "ar\t'r1,'r2");
+      break;
+    case SR:
+      Format(instr, "sr\t'r1,'r2");
+      break;
+    case MR:
+      Format(instr, "mr\t'r1,'r2");
+      break;
+    case DR:
+      Format(instr, "dr\t'r1,'r2");
+      break;
+    case OR:
+      Format(instr, "or\t'r1,'r2");
+      break;
+    case NR:
+      Format(instr, "nr\t'r1,'r2");
+      break;
+    case XR:
+      Format(instr, "xr\t'r1,'r2");
+      break;
+    case LR:
+      Format(instr, "lr\t'r1,'r2");
+      break;
+    case CR:
+      Format(instr, "cr\t'r1,'r2");
+      break;
+    case CLR:
+      Format(instr, "clr\t'r1,'r2");
+      break;
+    case BCR:
+      Format(instr, "bcr\t'm1,'r2");
+      break;
+    case LTR:
+      Format(instr, "ltr\t'r1,'r2");
+      break;
+    case ALR:
+      Format(instr, "alr\t'r1,'r2");
+      break;
+    case SLR:
+      Format(instr, "slr\t'r1,'r2");
+      break;
+    case LNR:
+      Format(instr, "lnr\t'r1,'r2");
+      break;
+    case LCR:
+      Format(instr, "lcr\t'r1,'r2");
+      break;
+    case BASR:
+      Format(instr, "basr\t'r1,'r2");
+      break;
+    case LDR:
+      Format(instr, "ldr\t'f1,'f2");
+      break;
+    case BKPT:
+      Format(instr, "bkpt");
+      break;
+    default:
+      return false;
+  }
+  return true;
+}
+
+// Disassembles Four Byte S390 Instructions
+// @return true if successfully decoded
+bool Decoder::DecodeFourByte(Instruction* instr) {
+  // Print the Instruction bits.
+  out_buffer_pos_ += SNPrintF(out_buffer_ + out_buffer_pos_, "%08x       ",
+                              instr->InstructionBits<FourByteInstr>());
+
+  Opcode opcode = instr->S390OpcodeValue();
+  switch (opcode) {
+    case AHI:
+      Format(instr, "ahi\t'r1,'i1");
+      break;
+    case AGHI:
+      Format(instr, "aghi\t'r1,'i1");
+      break;
+    case LHI:
+      Format(instr, "lhi\t'r1,'i1");
+      break;
+    case LGHI:
+      Format(instr, "lghi\t'r1,'i1");
+      break;
+    case MHI:
+      Format(instr, "mhi\t'r1,'i1");
+      break;
+    case MGHI:
+      Format(instr, "mghi\t'r1,'i1");
+      break;
+    case CHI:
+      Format(instr, "chi\t'r1,'i1");
+      break;
+    case CGHI:
+      Format(instr, "cghi\t'r1,'i1");
+      break;
+    case BRAS:
+      Format(instr, "bras\t'r1,'i1");
+      break;
+    case BRC:
+      Format(instr, "brc\t'm1,'i4");
+      break;
+    case BRCT:
+      Format(instr, "brct\t'r1,'i4");
+      break;
+    case BRCTG:
+      Format(instr, "brctg\t'r1,'i4");
+      break;
+    case IIHH:
+      Format(instr, "iihh\t'r1,'i1");
+      break;
+    case IIHL:
+      Format(instr, "iihl\t'r1,'i1");
+      break;
+    case IILH:
+      Format(instr, "iilh\t'r1,'i1");
+      break;
+    case IILL:
+      Format(instr, "iill\t'r1,'i1");
+      break;
+    case OILL:
+      Format(instr, "oill\t'r1,'i1");
+      break;
+    case TMLL:
+      Format(instr, "tmll\t'r1,'i1");
+      break;
+    case STM:
+      Format(instr, "stm\t'r1,'r2,'d1('r3)");
+      break;
+    case LM:
+      Format(instr, "lm\t'r1,'r2,'d1('r3)");
+      break;
+    case SLL:
+      Format(instr, "sll\t'r1,'d1('r3)");
+      break;
+    case SRL:
+      Format(instr, "srl\t'r1,'d1('r3)");
+      break;
+    case SLA:
+      Format(instr, "sla\t'r1,'d1('r3)");
+      break;
+    case SRA:
+      Format(instr, "sra\t'r1,'d1('r3)");
+      break;
+    case SLDL:
+      Format(instr, "sldl\t'r1,'d1('r3)");
+      break;
+    case AGR:
+      Format(instr, "agr\t'r5,'r6");
+      break;
+    case AGFR:
+      Format(instr, "agfr\t'r5,'r6");
+      break;
+    case ARK:
+      Format(instr, "ark\t'r5,'r6,'r3");
+      break;
+    case AGRK:
+      Format(instr, "agrk\t'r5,'r6,'r3");
+      break;
+    case SGR:
+      Format(instr, "sgr\t'r5,'r6");
+      break;
+    case SGFR:
+      Format(instr, "sgfr\t'r5,'r6");
+      break;
+    case SRK:
+      Format(instr, "srk\t'r5,'r6,'r3");
+      break;
+    case SGRK:
+      Format(instr, "sgrk\t'r5,'r6,'r3");
+      break;
+    case NGR:
+      Format(instr, "ngr\t'r5,'r6");
+      break;
+    case NRK:
+      Format(instr, "nrk\t'r5,'r6,'r3");
+      break;
+    case NGRK:
+      Format(instr, "ngrk\t'r5,'r6,'r3");
+      break;
+    case NILL:
+      Format(instr, "nill\t'r1,'i1");
+      break;
+    case NILH:
+      Format(instr, "nilh\t'r1,'i1");
+      break;
+    case OGR:
+      Format(instr, "ogr\t'r5,'r6");
+      break;
+    case ORK:
+      Format(instr, "ork\t'r5,'r6,'r3");
+      break;
+    case OGRK:
+      Format(instr, "ogrk\t'r5,'r6,'r3");
+      break;
+    case XGR:
+      Format(instr, "xgr\t'r5,'r6");
+      break;
+    case XRK:
+      Format(instr, "xrk\t'r5,'r6,'r3");
+      break;
+    case XGRK:
+      Format(instr, "xgrk\t'r5,'r6,'r3");
+      break;
+    case CGR:
+      Format(instr, "cgr\t'r5,'r6");
+      break;
+    case CLGR:
+      Format(instr, "clgr\t'r5,'r6");
+      break;
+    case LLGFR:
+      Format(instr, "llgfr\t'r5,'r6");
+      break;
+    case LBR:
+      Format(instr, "lbr\t'r5,'r6");
+      break;
+    case LEDBR:
+      Format(instr, "ledbr\t'f5,'f6");
+      break;
+    case LDEBR:
+      Format(instr, "ldebr\t'f5,'f6");
+      break;
+    case LTGR:
+      Format(instr, "ltgr\t'r5,'r6");
+      break;
+    case LTDBR:
+      Format(instr, "ltdbr\t'f5,'f6");
+      break;
+    case LTEBR:
+      Format(instr, "ltebr\t'f5,'f6");
+      break;
+    case LGR:
+      Format(instr, "lgr\t'r5,'r6");
+      break;
+    case LGDR:
+      Format(instr, "lgdr\t'r5,'f6");
+      break;
+    case LGFR:
+      Format(instr, "lgfr\t'r5,'r6");
+      break;
+    case LTGFR:
+      Format(instr, "ltgfr\t'r5,'r6");
+      break;
+    case LCGR:
+      Format(instr, "lcgr\t'r5,'r6");
+      break;
+    case MSR:
+      Format(instr, "msr\t'r5,'r6");
+      break;
+    case LGBR:
+      Format(instr, "lgbr\t'r5,'r6");
+      break;
+    case LGHR:
+      Format(instr, "lghr\t'r5,'r6");
+      break;
+    case MSGR:
+      Format(instr, "msgr\t'r5,'r6");
+      break;
+    case DSGR:
+      Format(instr, "dsgr\t'r5,'r6");
+      break;
+    case LZDR:
+      Format(instr, "lzdr\t'f5");
+      break;
+    case MLR:
+      Format(instr, "mlr\t'r5,'r6");
+      break;
+    case MLGR:
+      Format(instr, "mlgr\t'r5,'r6");
+      break;
+    case ALCR:
+      Format(instr, "alcr\t'r5,'r6");
+      break;
+    case ALGR:
+      Format(instr, "algr\t'r5,'r6");
+      break;
+    case ALRK:
+      Format(instr, "alrk\t'r5,'r6,'r3");
+      break;
+    case ALGRK:
+      Format(instr, "algrk\t'r5,'r6,'r3");
+      break;
+    case SLGR:
+      Format(instr, "slgr\t'r5,'r6");
+      break;
+    case SLBR:
+      Format(instr, "slbr\t'r5,'r6");
+      break;
+    case DLR:
+      Format(instr, "dlr\t'r5,'r6");
+      break;
+    case DLGR:
+      Format(instr, "dlgr\t'r5,'r6");
+      break;
+    case SLRK:
+      Format(instr, "slrk\t'r5,'r6,'r3");
+      break;
+    case SLGRK:
+      Format(instr, "slgrk\t'r5,'r6,'r3");
+      break;
+    case LHR:
+      Format(instr, "lhr\t'r5,'r6");
+      break;
+    case LLHR:
+      Format(instr, "llhr\t'r5,'r6");
+      break;
+    case LLGHR:
+      Format(instr, "llghr\t'r5,'r6");
+      break;
+    case LNGR:
+      Format(instr, "lngr\t'r5,'r6");
+      break;
+    case A:
+      Format(instr, "a\t'r1,'d1('r2d,'r3)");
+      break;
+    case S:
+      Format(instr, "s\t'r1,'d1('r2d,'r3)");
+      break;
+    case M:
+      Format(instr, "m\t'r1,'d1('r2d,'r3)");
+      break;
+    case D:
+      Format(instr, "d\t'r1,'d1('r2d,'r3)");
+      break;
+    case O:
+      Format(instr, "o\t'r1,'d1('r2d,'r3)");
+      break;
+    case N:
+      Format(instr, "n\t'r1,'d1('r2d,'r3)");
+      break;
+    case L:
+      Format(instr, "l\t'r1,'d1('r2d,'r3)");
+      break;
+    case C:
+      Format(instr, "c\t'r1,'d1('r2d,'r3)");
+      break;
+    case AH:
+      Format(instr, "ah\t'r1,'d1('r2d,'r3)");
+      break;
+    case SH:
+      Format(instr, "sh\t'r1,'d1('r2d,'r3)");
+      break;
+    case MH:
+      Format(instr, "mh\t'r1,'d1('r2d,'r3)");
+      break;
+    case AL:
+      Format(instr, "al\t'r1,'d1('r2d,'r3)");
+      break;
+    case SL:
+      Format(instr, "sl\t'r1,'d1('r2d,'r3)");
+      break;
+    case LA:
+      Format(instr, "la\t'r1,'d1('r2d,'r3)");
+      break;
+    case CH:
+      Format(instr, "ch\t'r1,'d1('r2d,'r3)");
+      break;
+    case CL:
+      Format(instr, "cl\t'r1,'d1('r2d,'r3)");
+      break;
+    case CLI:
+      Format(instr, "cli\t'd1('r3),'i8");
+      break;
+    case TM:
+      Format(instr, "tm\t'd1('r3),'i8");
+      break;
+    case BC:
+      Format(instr, "bc\t'm1,'d1('r2d,'r3)");
+      break;
+    case BCT:
+      Format(instr, "bct\t'r1,'d1('r2d,'r3)");
+      break;
+    case ST:
+      Format(instr, "st\t'r1,'d1('r2d,'r3)");
+      break;
+    case STC:
+      Format(instr, "stc\t'r1,'d1('r2d,'r3)");
+      break;
+    case IC_z:
+      Format(instr, "ic\t'r1,'d1('r2d,'r3)");
+      break;
+    case LD:
+      Format(instr, "ld\t'f1,'d1('r2d,'r3)");
+      break;
+    case LE:
+      Format(instr, "le\t'f1,'d1('r2d,'r3)");
+      break;
+    case LDGR:
+      Format(instr, "ldgr\t'f5,'r6");
+      break;
+    case STE:
+      Format(instr, "ste\t'f1,'d1('r2d,'r3)");
+      break;
+    case STD:
+      Format(instr, "std\t'f1,'d1('r2d,'r3)");
+      break;
+    case CFDBR:
+      Format(instr, "cfdbr\t'r5,'m2,'f6");
+      break;
+    case CDFBR:
+      Format(instr, "cdfbr\t'f5,'m2,'r6");
+      break;
+    case CFEBR:
+      Format(instr, "cfebr\t'r5,'m2,'f6");
+      break;
+    case CEFBR:
+      Format(instr, "cefbr\t'f5,'m2,'r6");
+      break;
+    case CGEBR:
+      Format(instr, "cgebr\t'r5,'m2,'f6");
+      break;
+    case CGDBR:
+      Format(instr, "cgdbr\t'r5,'m2,'f6");
+      break;
+    case CEGBR:
+      Format(instr, "cegbr\t'f5,'m2,'r6");
+      break;
+    case CDGBR:
+      Format(instr, "cdgbr\t'f5,'m2,'r6");
+      break;
+    case CDLFBR:
+      Format(instr, "cdlfbr\t'f5,'m2,'r6");
+      break;
+    case CDLGBR:
+      Format(instr, "cdlgbr\t'f5,'m2,'r6");
+      break;
+    case CELGBR:
+      Format(instr, "celgbr\t'f5,'m2,'r6");
+      break;
+    case CLFDBR:
+      Format(instr, "clfdbr\t'r5,'m2,'f6");
+      break;
+    case CLGDBR:
+      Format(instr, "clgdbr\t'r5,'m2,'f6");
+      break;
+    case AEBR:
+      Format(instr, "aebr\t'f5,'f6");
+      break;
+    case SEBR:
+      Format(instr, "sebr\t'f5,'f6");
+      break;
+    case MEEBR:
+      Format(instr, "meebr\t'f5,'f6");
+      break;
+    case DEBR:
+      Format(instr, "debr\t'f5,'f6");
+      break;
+    case ADBR:
+      Format(instr, "adbr\t'f5,'f6");
+      break;
+    case SDBR:
+      Format(instr, "sdbr\t'f5,'f6");
+      break;
+    case MDBR:
+      Format(instr, "mdbr\t'f5,'f6");
+      break;
+    case DDBR:
+      Format(instr, "ddbr\t'f5,'f6");
+      break;
+    case CDBR:
+      Format(instr, "cdbr\t'f5,'f6");
+      break;
+    case CEBR:
+      Format(instr, "cebr\t'f5,'f6");
+      break;
+    case SQDBR:
+      Format(instr, "sqdbr\t'f5,'f6");
+      break;
+    case SQEBR:
+      Format(instr, "sqebr\t'f5,'f6");
+      break;
+    case LCDBR:
+      Format(instr, "lcdbr\t'f5,'f6");
+      break;
+    case STH:
+      Format(instr, "sth\t'r1,'d1('r2d,'r3)");
+      break;
+    case SRDA:
+      Format(instr, "srda\t'r1,'d1('r3)");
+      break;
+    case SRDL:
+      Format(instr, "srdl\t'r1,'d1('r3)");
+      break;
+    case MADBR:
+      Format(instr, "madbr\t'f3,'f5,'f6");
+      break;
+    case MSDBR:
+      Format(instr, "msdbr\t'f3,'f5,'f6");
+      break;
+    case FLOGR:
+      Format(instr, "flogr\t'r5,'r6");
+      break;
+    case FIEBRA:
+      Format(instr, "fiebra\t'f5,'m2,'f6,'m3");
+      break;
+    case FIDBRA:
+      Format(instr, "fidbra\t'f5,'m2,'f6,'m3");
+      break;
+    // TRAP4 is used in calling to native function. it will not be generated
+    // in native code.
+    case TRAP4: {
+      Format(instr, "trap4");
+      break;
+    }
+    default:
+      return false;
+  }
+  return true;
+}
+
+// Disassembles Six Byte S390 Instructions
+// @return true if successfully decoded
+bool Decoder::DecodeSixByte(Instruction* instr) {
+  // Print the Instruction bits.
+  out_buffer_pos_ +=
+      SNPrintF(out_buffer_ + out_buffer_pos_, "%012" PRIx64 "   ",
+               instr->InstructionBits<SixByteInstr>());
+
+  Opcode opcode = instr->S390OpcodeValue();
+  switch (opcode) {
+    case LLILF:
+      Format(instr, "llilf\t'r1,'i7");
+      break;
+    case LLIHF:
+      Format(instr, "llihf\t'r1,'i7");
+      break;
+    case AFI:
+      Format(instr, "afi\t'r1,'i7");
+      break;
+    case ASI:
+      Format(instr, "asi\t'd2('r3),'ic");
+      break;
+    case AGSI:
+      Format(instr, "agsi\t'd2('r3),'ic");
+      break;
+    case ALFI:
+      Format(instr, "alfi\t'r1,'i7");
+      break;
+    case AHIK:
+      Format(instr, "ahik\t'r1,'r2,'i1");
+      break;
+    case AGHIK:
+      Format(instr, "aghik\t'r1,'r2,'i1");
+      break;
+    case CLGFI:
+      Format(instr, "clgfi\t'r1,'i7");
+      break;
+    case CLFI:
+      Format(instr, "clfi\t'r1,'i7");
+      break;
+    case CFI:
+      Format(instr, "cfi\t'r1,'i2");
+      break;
+    case CGFI:
+      Format(instr, "cgfi\t'r1,'i2");
+      break;
+    case BRASL:
+      Format(instr, "brasl\t'r1,'ie");
+      break;
+    case BRCL:
+      Format(instr, "brcl\t'm1,'i5");
+      break;
+    case IIHF:
+      Format(instr, "iihf\t'r1,'i7");
+      break;
+    case IILF:
+      Format(instr, "iilf\t'r1,'i7");
+      break;
+    case XIHF:
+      Format(instr, "xihf\t'r1,'i7");
+      break;
+    case XILF:
+      Format(instr, "xilf\t'r1,'i7");
+      break;
+    case SLLK:
+      Format(instr, "sllk\t'r1,'r2,'d2('r3)");
+      break;
+    case SLLG:
+      Format(instr, "sllg\t'r1,'r2,'d2('r3)");
+      break;
+    case RLL:
+      Format(instr, "rll\t'r1,'r2,'d2('r3)");
+      break;
+    case RLLG:
+      Format(instr, "rllg\t'r1,'r2,'d2('r3)");
+      break;
+    case SRLK:
+      Format(instr, "srlk\t'r1,'r2,'d2('r3)");
+      break;
+    case SRLG:
+      Format(instr, "srlg\t'r1,'r2,'d2('r3)");
+      break;
+    case SLAK:
+      Format(instr, "slak\t'r1,'r2,'d2('r3)");
+      break;
+    case SLAG:
+      Format(instr, "slag\t'r1,'r2,'d2('r3)");
+      break;
+    case SRAK:
+      Format(instr, "srak\t'r1,'r2,'d2('r3)");
+      break;
+    case SRAG:
+      Format(instr, "srag\t'r1,'r2,'d2('r3)");
+      break;
+    case RISBG:
+      Format(instr, "risbg\t'r1,'r2,'i9,'ia,'ib");
+      break;
+    case RISBGN:
+      Format(instr, "risbgn\t'r1,'r2,'i9,'ia,'ib");
+      break;
+    case LMY:
+      Format(instr, "lmy\t'r1,'r2,'d2('r3)");
+      break;
+    case LMG:
+      Format(instr, "lmg\t'r1,'r2,'d2('r3)");
+      break;
+    case STMY:
+      Format(instr, "stmy\t'r1,'r2,'d2('r3)");
+      break;
+    case STMG:
+      Format(instr, "stmg\t'r1,'r2,'d2('r3)");
+      break;
+    case LT:
+      Format(instr, "lt\t'r1,'d2('r2d,'r3)");
+      break;
+    case LTG:
+      Format(instr, "ltg\t'r1,'d2('r2d,'r3)");
+      break;
+    case ML:
+      Format(instr, "ml\t'r1,'d2('r2d,'r3)");
+      break;
+    case AY:
+      Format(instr, "ay\t'r1,'d2('r2d,'r3)");
+      break;
+    case SY:
+      Format(instr, "sy\t'r1,'d2('r2d,'r3)");
+      break;
+    case NY:
+      Format(instr, "ny\t'r1,'d2('r2d,'r3)");
+      break;
+    case OY:
+      Format(instr, "oy\t'r1,'d2('r2d,'r3)");
+      break;
+    case XY:
+      Format(instr, "xy\t'r1,'d2('r2d,'r3)");
+      break;
+    case CY:
+      Format(instr, "cy\t'r1,'d2('r2d,'r3)");
+      break;
+    case AHY:
+      Format(instr, "ahy\t'r1,'d2('r2d,'r3)");
+      break;
+    case SHY:
+      Format(instr, "shy\t'r1,'d2('r2d,'r3)");
+      break;
+    case LGH:
+      Format(instr, "lgh\t'r1,'d2('r2d,'r3)");
+      break;
+    case AG:
+      Format(instr, "ag\t'r1,'d2('r2d,'r3)");
+      break;
+    case AGF:
+      Format(instr, "agf\t'r1,'d2('r2d,'r3)");
+      break;
+    case SG:
+      Format(instr, "sg\t'r1,'d2('r2d,'r3)");
+      break;
+    case NG:
+      Format(instr, "ng\t'r1,'d2('r2d,'r3)");
+      break;
+    case OG:
+      Format(instr, "og\t'r1,'d2('r2d,'r3)");
+      break;
+    case XG:
+      Format(instr, "xg\t'r1,'d2('r2d,'r3)");
+      break;
+    case CG:
+      Format(instr, "cg\t'r1,'d2('r2d,'r3)");
+      break;
+    case LB:
+      Format(instr, "lb\t'r1,'d2('r2d,'r3)");
+      break;
+    case LG:
+      Format(instr, "lg\t'r1,'d2('r2d,'r3)");
+      break;
+    case LGF:
+      Format(instr, "lgf\t'r1,'d2('r2d,'r3)");
+      break;
+    case LLGF:
+      Format(instr, "llgf\t'r1,'d2('r2d,'r3)");
+      break;
+    case LY:
+      Format(instr, "ly\t'r1,'d2('r2d,'r3)");
+      break;
+    case ALY:
+      Format(instr, "aly\t'r1,'d2('r2d,'r3)");
+      break;
+    case ALG:
+      Format(instr, "alg\t'r1,'d2('r2d,'r3)");
+      break;
+    case SLG:
+      Format(instr, "slg\t'r1,'d2('r2d,'r3)");
+      break;
+    case SGF:
+      Format(instr, "sgf\t'r1,'d2('r2d,'r3)");
+      break;
+    case SLY:
+      Format(instr, "sly\t'r1,'d2('r2d,'r3)");
+      break;
+    case LLH:
+      Format(instr, "llh\t'r1,'d2('r2d,'r3)");
+      break;
+    case LLGH:
+      Format(instr, "llgh\t'r1,'d2('r2d,'r3)");
+      break;
+    case LLC:
+      Format(instr, "llc\t'r1,'d2('r2d,'r3)");
+      break;
+    case LLGC:
+      Format(instr, "llgc\t'r1,'d2('r2d,'r3)");
+      break;
+    case LDEB:
+      Format(instr, "ldeb\t'f1,'d2('r2d,'r3)");
+      break;
+    case LAY:
+      Format(instr, "lay\t'r1,'d2('r2d,'r3)");
+      break;
+    case LARL:
+      Format(instr, "larl\t'r1,'i5");
+      break;
+    case LGB:
+      Format(instr, "lgb\t'r1,'d2('r2d,'r3)");
+      break;
+    case CHY:
+      Format(instr, "chy\t'r1,'d2('r2d,'r3)");
+      break;
+    case CLY:
+      Format(instr, "cly\t'r1,'d2('r2d,'r3)");
+      break;
+    case CLIY:
+      Format(instr, "cliy\t'd2('r3),'i8");
+      break;
+    case TMY:
+      Format(instr, "tmy\t'd2('r3),'i8");
+      break;
+    case CLG:
+      Format(instr, "clg\t'r1,'d2('r2d,'r3)");
+      break;
+    case BCTG:
+      Format(instr, "bctg\t'r1,'d2('r2d,'r3)");
+      break;
+    case STY:
+      Format(instr, "sty\t'r1,'d2('r2d,'r3)");
+      break;
+    case STG:
+      Format(instr, "stg\t'r1,'d2('r2d,'r3)");
+      break;
+    case ICY:
+      Format(instr, "icy\t'r1,'d2('r2d,'r3)");
+      break;
+    case MVC:
+      Format(instr, "mvc\t'd3('i8,'r3),'d4('r7)");
+      break;
+    case MVHI:
+      Format(instr, "mvhi\t'd3('r3),'id");
+      break;
+    case MVGHI:
+      Format(instr, "mvghi\t'd3('r3),'id");
+      break;
+    case ALGFI:
+      Format(instr, "algfi\t'r1,'i7");
+      break;
+    case SLGFI:
+      Format(instr, "slgfi\t'r1,'i7");
+      break;
+    case SLFI:
+      Format(instr, "slfi\t'r1,'i7");
+      break;
+    case NIHF:
+      Format(instr, "nihf\t'r1,'i7");
+      break;
+    case NILF:
+      Format(instr, "nilf\t'r1,'i7");
+      break;
+    case OIHF:
+      Format(instr, "oihf\t'r1,'i7");
+      break;
+    case OILF:
+      Format(instr, "oilf\t'r1,'i7");
+      break;
+    case MSFI:
+      Format(instr, "msfi\t'r1,'i7");
+      break;
+    case MSGFI:
+      Format(instr, "msgfi\t'r1,'i7");
+      break;
+    case LDY:
+      Format(instr, "ldy\t'f1,'d2('r2d,'r3)");
+      break;
+    case LEY:
+      Format(instr, "ley\t'f1,'d2('r2d,'r3)");
+      break;
+    case STEY:
+      Format(instr, "stey\t'f1,'d2('r2d,'r3)");
+      break;
+    case STDY:
+      Format(instr, "stdy\t'f1,'d2('r2d,'r3)");
+      break;
+    case ADB:
+      Format(instr, "adb\t'r1,'d1('r2d, 'r3)");
+      break;
+    case SDB:
+      Format(instr, "sdb\t'r1,'d1('r2d, 'r3)");
+      break;
+    case MDB:
+      Format(instr, "mdb\t'r1,'d1('r2d, 'r3)");
+      break;
+    case DDB:
+      Format(instr, "ddb\t'r1,'d1('r2d, 'r3)");
+      break;
+    case SQDB:
+      Format(instr, "sqdb\t'r1,'d1('r2d, 'r3)");
+      break;
+    default:
+      return false;
+  }
+  return true;
+}
+
+#undef VERIFIY
+
+// Disassemble the instruction at *instr_ptr into the output buffer.
+int Decoder::InstructionDecode(byte* instr_ptr) {
+  Instruction* instr = Instruction::At(instr_ptr);
+  int instrLength = instr->InstructionLength();
+
+  if (2 == instrLength)
+    DecodeTwoByte(instr);
+  else if (4 == instrLength)
+    DecodeFourByte(instr);
+  else
+    DecodeSixByte(instr);
+
+  return instrLength;
+}
+
+}  // namespace internal
+}  // namespace v8
+
+//------------------------------------------------------------------------------
+
+namespace disasm {
+
+const char* NameConverter::NameOfAddress(byte* addr) const {
+  v8::internal::SNPrintF(tmp_buffer_, "%p", addr);
+  return tmp_buffer_.start();
+}
+
+const char* NameConverter::NameOfConstant(byte* addr) const {
+  return NameOfAddress(addr);
+}
+
+const char* NameConverter::NameOfCPURegister(int reg) const {
+  return v8::internal::Register::from_code(reg).ToString();
+}
+
+const char* NameConverter::NameOfByteCPURegister(int reg) const {
+  UNREACHABLE();  // S390 does not have the concept of a byte register
+  return "nobytereg";
+}
+
+const char* NameConverter::NameOfXMMRegister(int reg) const {
+  // S390 does not have XMM register
+  // TODO(joransiu): Consider update this for Vector Regs
+  UNREACHABLE();
+  return "noxmmreg";
+}
+
+const char* NameConverter::NameInCode(byte* addr) const {
+  // The default name converter is called for unknown code. So we will not try
+  // to access any memory.
+  return "";
+}
+
+//------------------------------------------------------------------------------
+
+Disassembler::Disassembler(const NameConverter& converter)
+    : converter_(converter) {}
+
+Disassembler::~Disassembler() {}
+
+int Disassembler::InstructionDecode(v8::internal::Vector<char> buffer,
+                                    byte* instruction) {
+  v8::internal::Decoder d(converter_, buffer);
+  return d.InstructionDecode(instruction);
+}
+
+// The S390 assembler does not currently use constant pools.
+int Disassembler::ConstantPoolSizeAt(byte* instruction) { return -1; }
+
+void Disassembler::Disassemble(FILE* f, byte* begin, byte* end) {
+  NameConverter converter;
+  Disassembler d(converter);
+  for (byte* pc = begin; pc < end;) {
+    v8::internal::EmbeddedVector<char, 128> buffer;
+    buffer[0] = '\0';
+    byte* prev_pc = pc;
+    pc += d.InstructionDecode(buffer, pc);
+    v8::internal::PrintF(f, "%p    %08x      %s\n", prev_pc,
+                         *reinterpret_cast<int32_t*>(prev_pc), buffer.start());
+  }
+}
+
+}  // namespace disasm
+
+#endif  // V8_TARGET_ARCH_S390