mainline build failure of powerpc allmodconfig for prom_init_check

[Linus Torvalds]

On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee
<sudipm.mukherjee at gmail.com> wrote:
>
> I was trying to check it. With gcc-11 the assembly code generated is
> not using memset, but using __memset.
> But with gcc-12, I can see the assembly code is using memset. One
> example from the assembly:

You could try making the 'args' array in 'struct prom_args' be marked
'volatile'.

Ie something like this:

  --- a/arch/powerpc/kernel/prom_init.c
  +++ b/arch/powerpc/kernel/prom_init.c
  @@ -115,6 +115,6 @@ struct prom_args {
           __be32 service;
           __be32 nargs;
           __be32 nret;
  -          __be32 args[10];
  +        volatile __be32 args[10];
   };

because I think it's just the compilers turning the small loop over
those fields into a "memset()".

              Linus