[02/19] RISC-V: fold redundant code in riscv_ip()

[Jan Beulich]

On 28.04.2026 03:52, Jiawei wrote:
>> The parsing of 'F' and 'O' .insn operands is pretty redundant. Have only a
>> single instance each of common code, with the inner switch()es merely
>> handling the actual value insertion. This in particular simplifies the
>> addition of new sub-forms.
>> ---
>> Since it's entirely internal, can't we rename O4 to either O7 or
>> (describing merely the non-fixed bits) O5? I wonder why O4 was used in the
>> first place ...
>>
> 
> The refactoring looks reasonable overall, but I have one question about the
> O2 case.
> 
> Before this change, O2 rejected values >= 3, so the accepted range was
> 0...2. With the new common check based on 1U << regno, O2 now accepts
> 0...3.
> 
> Is this intended? If O2 is meant to describe a two-bit field, then the new
> range looks natural, but the old code seemed to deliberately reject 3.
I've fixed this.

> The O4 part looks equivalent to me, apart from the split diagnostics. I also
> agree that O4 is a misleading internal name; O7 would make the field width
> clearer if we decide to rename it in a follow-up.

For this I'm rather inclined to insert a patch ahead of this one. Then the
odd

	      /* O4 is a misnomer, really describing a 7-bit field.  */
	      if (regno == 4)
		regno += 3;

won't even need introducing (just to later delete it again).

Jan