Re: [PATCH 3/3] opcodes/i386: partially implement disassembler style support

[Jan Beulich <jbeulich@suse.com>]

On 17.02.2022 17:15, Andrew Burgess wrote:
> Jan Beulich via Binutils <binutils@sourceware.org> writes:
>> On 16.02.2022 21:53, Andrew Burgess via Binutils wrote:
>>> @@ -9456,12 +9456,18 @@ print_insn (bfd_vma pc, instr_info *ins)
>>>  	{
>>>  	  name = prefix_name (ins, priv.the_buffer[0], priv.orig_sizeflag);
>>>  	  if (name != NULL)
>>> -	    (*ins->info->fprintf_func) (ins->info->stream, "%s", name);
>>> +	    (*ins->info->fprintf_styled_func)
>>> +	      (ins->info->stream, dis_style_mnemonic, "%s", name);
>>>  	  else
>>>  	    {
>>>  	      /* Just print the first byte as a .byte instruction.  */
>>> -	      (*ins->info->fprintf_func) (ins->info->stream, ".byte 0x%x",
>>> -				     (unsigned int) priv.the_buffer[0]);
>>> +	      (*ins->info->fprintf_styled_func)
>>> +		(ins->info->stream, dis_style_mnemonic, ".byte");
>>
>> Perhaps better have dis_style_directive for this? It's certainly not
>> an insn mnemonic.
> 
> Are you suggesting directive in addition to mnemonic?  Or as a
> replacement for?

In addition to. They're fundamentally different things at the
assembler level. But that's just my view ...

> My goal with the style list was to try and keep the number of styles
> pretty small, an instrution mnemonic like 'add' and a directive like
> '.byte' seemed to have a similar enough function that styling them
> identically felt OK.
> 
>>
>>> +	      (*ins->info->fprintf_styled_func)
>>> +		(ins->info->stream, dis_style_text, " ");
>>> +	      (*ins->info->fprintf_styled_func)
>>> +		(ins->info->stream, dis_style_immediate, "0x%x",
>>> +		 (unsigned int) priv.the_buffer[0]);
>>
>> I wonder if the naming (dis_style_immediate) isn't misleading. As per
>> the comment next to its definition it really appears to mean any kind
>> of number (like is the case here), not just immediate operands of
>> instructions. Hence maybe dis_style_number (as replacement for or in
>> addition to dis_style_immediate)?
> 
> You mentioned this before in the previous thread, and I didn't really
> understand then either.
> 
> Can you give an example of something that's a number, but not an
> immediate?  e.g. I wonder (given the instruction/directive distinction
> you draw above), I wonder if you're conserned about: '.byte 0x4', maybe
> you don't like referring to this 0x4 here as an immediate?

Well, an operand to a directive for example is not an immediate imo,
yes. A "load offset" (as your comment calls it) may also not be an
immediate. E.g. in x86 memory access instructions:

	mov	0x10(%rbx), %eax

the 0x10 isn't an immediate, but a displacement. The difference may
be more relevant in something like

	mov	$0, 0x10(%rbx)

where the $0 is an immediate operand, but the 0x10 isn't (and you
wouldn't want to mix the two).

From that comment it's not clear to me where else you would think
"immediate" applies (or not), but in RISC-V's

	lw	x0, 0x10(x0)

I wouldn't consider the 0x10 an immediate either, albeit this may
be a result of my x86 bias.

Jan