Can the "ATTRIBUTE_UNUSED" macro be removed if the paramter has being used in fact

[Hu, Jiangping]

Hi, 

I find there are many "ATTRIBUTE_UNUSED" macros in the function parameter lists,
but some of the parameters are used in the function bodies in fact.  E.g.

  @@gcc/final.c
  void
  output_operand (rtx x, int code ATTRIBUTE_UNUSED)
  {
    if (x && GET_CODE (x) == SUBREG)
      x = alter_subreg (&x, true);

    /* X must not be a pseudo reg.  */
    if (!targetm.no_register_allocation)
      gcc_assert (!x || !REG_P (x) || REGNO (x) < FIRST_PSEUDO_REGISTER);

    targetm.asm_out.print_operand (asm_out_file, x, code);

    if (x == NULL_RTX)
      return;

    mark_symbol_refs_as_used (x);
  }

I know there are no compile issues for the code above, and if we read the body,
it will not cause too much trouble to readers.
So I don't know if can I make a patch to remove that? If it is approved, 
can I just firstly change the files I encountered, because I think many files 
may have this situation, it's hard to address all of them in 1 patch.

Regards!
Hujp