Re: [PATCH 2/3] powerpc: fix build errors

Nicholas Piggin
2022-02-25T00:23:16Z

Excerpts from Segher Boessenkool's message of February 25, 2022 3:29 am:
> On Thu, Feb 24, 2022 at 09:13:25PM +1000, Nicholas Piggin wrote:
>> Excerpts from Arnd Bergmann's message of February 24, 2022 8:20 pm:
>> > Again, there should be a minimum number of those .machine directives
>> > in inline asm as well, which tends to work out fine as long as the
>> > entire kernel is built with the correct -march= option for the minimum
>> > supported CPU, and stays away from inline asm that requires a higher
>> > CPU level.
>>
>> There's really no advantage to them, and they're ugly and annoying
>> and if we applied the concept consistently for all asm they would grow
>> to a very large number.
>
> The advantage is that you get machine code that *works*. There are
> quite a few mnemonics that translate to different instructions with
> different machine options! We like to get the intended instructions
> instead of something that depends on what assembler options the user
> has passed behind our backs.
>
>> The idea they'll give you good static checking just doesn't really
>> pan out.
>
> That never was a goal of this at all.
>
> -many was very problematical for GCC itself. We no longer use it.

You have the wrong context. We're not talking about -many vs .machine
here.

Thanks,
Nick