Support multi-byte nop instructions as recommended by

src/ia32/assembler-ia32.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 641 matching lines @@
   // is: should we always use Operands instead of Registers where an
   // Operand is possible, or should we have a Register (overloaded) form
   // instead? We must be careful to make sure that the selected instruction
   // is obvious from the parameters to avoid hard-to-find code generation
   // bugs.
 
   // Insert the smallest number of nop instructions
   // possible to align the pc offset to a multiple
   // of m. m must be a power of 2.
   void Align(int m);
+  void Nop(int bytes = 1);
   // Aligns code to something that's optimal for a jump target for the platform.
   void CodeTargetAlign();
 
   // Stack
   void pushad();
   void popad();
 
   void pushfd();
   void popfd();
 
@@ skipping 401 matching lines @@
   int pc_offset() const { return pc_ - buffer_; }
 
   // Check if there is less than kGap bytes available in the buffer.
   // If this is the case, we need to grow the buffer before emitting
   // an instruction or relocation information.
   inline bool overflow() const { return pc_ >= reloc_info_writer.pos() - kGap; }
 
   // Get the number of bytes available in the buffer.
   inline int available_space() const { return reloc_info_writer.pos() - pc_; }
 
-  static bool IsNop(Address addr) { return *addr == 0x90; }
+  static bool IsNop(Address addr);
 
   PositionsRecorder* positions_recorder() { return &positions_recorder_; }
 
   int relocation_writer_size() {
     return (buffer_ + buffer_size_) - reloc_info_writer.pos();
   }
 
   // Avoid overflows for displacements etc.
   static const int kMaximalBufferSize = 512*MB;
   static const int kMinimalBufferSize = 4*KB;
@@ skipping 106 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_ASSEMBLER_IA32_H_