A64: Don't use a 'debug' instruction to implement the 'trace_sim' option.

src/a64/code-stubs-a64.cc

 // Copyright 2013 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 2891 matching lines @@
 //   x1: function.
 //   x2: receiver.
 //   x3: argc.
 //   x4: argv.
 // Output:
 //   x0: result.
 void JSEntryStub::GenerateBody(MacroAssembler* masm, bool is_construct) {
   ASSERT(jssp.Is(__ StackPointer()));
   Register code_entry = x0;
 
-  // TODO(all): We shouldn't emit debug instructions unconditionally since they
-  // will not work outside the simulator. We need to rethink how these commands
-  // interact with --trace-sim. For now, though, this turns on instruction
-  // tracing _if_ --trace-sim is specified.
-  __ Debug("TRACE ENTRY", 0, TRACE_ENABLE | LOG_ALL);
-
   // Enable instruction instrumentation. This only works on the simulator, and
   // will have no effect on the model or real hardware.
   __ EnableInstrumentation();
 
   Label invoke, handler_entry, exit;
 
   // Push callee-saved registers and synchronize the system stack pointer (csp)
   // and the JavaScript stack pointer (jssp).
   //
   // We must not write to jssp until after the PushCalleeSavedRegisters()
@@ skipping 4330 matching lines @@
   __ Bind(&fast_elements_case);
   GenerateCase(masm, FAST_ELEMENTS);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_A64