s390: introduce DUMY opcode for special use.

src/s390/disasm-s390.cc

 // 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.
 //
@@ skipping 1034 matching lines @@
 // 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 DUMY:
+      Format(instr, "dumy\t'r1, 'd2 ( 'r2d, 'r3 )");
+      break;
     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:
@@ skipping 409 matching lines @@
     byte* prev_pc = pc;
     pc += d.InstructionDecode(buffer, pc);
     v8::internal::PrintF(f, "%p    %08x      %s\n", static_cast<void*>(prev_pc),
                          *reinterpret_cast<int32_t*>(prev_pc), buffer.start());
   }
 }
 
 }  // namespace disasm
 
 #endif  // V8_TARGET_ARCH_S390