Clean up multi byte nop support on x64 to more closely match IA32.

src/x64/debug-x64.cc

 // Copyright 2011 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 246 matching lines @@
   // -----------------------------------
   Generate_DebugBreakCallHelper(masm, rdi.bit(), 0, false);
 }
 
 
 void Debug::GenerateSlot(MacroAssembler* masm) {
   // Generate enough nop's to make space for a call instruction.
   Label check_codesize;
   __ bind(&check_codesize);
   __ RecordDebugBreakSlot();
-  for (int i = 0; i < Assembler::kDebugBreakSlotLength; i++) {
-    __ nop();
-  }
+  __ Nop(Assembler::kDebugBreakSlotLength);
   ASSERT_EQ(Assembler::kDebugBreakSlotLength,
             masm->SizeOfCodeGeneratedSince(&check_codesize));
 }
 
 
 void Debug::GenerateSlotDebugBreak(MacroAssembler* masm) {
   // In the places where a debug break slot is inserted no registers can contain
   // object pointers.
   Generate_DebugBreakCallHelper(masm, 0, 0, true);
 }
@@ skipping 31 matching lines @@
 
 const bool Debug::kFrameDropperSupported = true;
 
 #undef __
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64