linux-kernel - Re: [PATCH] powerpc: sstep: Mark variable `rc` as unused in function 'analyse

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Message-ID: <CA+7wUsw+pmeS-oG5MMMjKB34R98vqHf1jxT=Fmx5oxiGLnYzBQ@mail.gmail.com>
Date:   Wed, 13 Mar 2019 21:12:15 +0100
From:   Mathieu Malaterre <malat@...ian.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc: sstep: Mark variable `rc` as unused in function 'analyse_instr'

On Tue, Mar 12, 2019 at 10:26 PM Christophe Leroy
<christophe.leroy@....fr> wrote:
>
>
>
> Le 12/03/2019 à 22:12, Mathieu Malaterre a écrit :
> > On Tue, Mar 12, 2019 at 9:56 PM Christophe Leroy
> > <christophe.leroy@....fr> wrote:
> >>
> >>
> >>
> >> Le 12/03/2019 à 21:20, Mathieu Malaterre a écrit :
> >>> Add gcc attribute unused for `rc` variable.
> >>>
> >>> Fix warnings treated as errors with W=1:
> >>>
> >>>     arch/powerpc/lib/sstep.c:1172:31: error: variable 'rc' set but not used [-Werror=unused-but-set-variable]
> >>>
> >>> Signed-off-by: Mathieu Malaterre <malat@...ian.org>
> >>> ---
> >>>    arch/powerpc/lib/sstep.c | 2 +-
> >>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> >>> index 3d33fb509ef4..32d092f62ae0 100644
> >>> --- a/arch/powerpc/lib/sstep.c
> >>> +++ b/arch/powerpc/lib/sstep.c
> >>> @@ -1169,7 +1169,7 @@ static nokprobe_inline int trap_compare(long v1, long v2)
> >>>    int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
> >>>                  unsigned int instr)
> >>>    {
> >>> -     unsigned int opcode, ra, rb, rc, rd, spr, u;
> >>> +     unsigned int opcode, ra, rb, rc __maybe_unused, rd, spr, u;
> >>
> >> I think it would be better to enclose 'rc' inside a #ifdef CONFIG_PPC64
> >
> > Hum odd, I would have bet you would have suggested me to use
> > IS_ENABLED with some crazy scheme (I was not able to mix it with the
> > switch case nicely).
>
> Well I guess yes, you could also get rid of the #ifdef __powerpc64__ and
> instead add the following just after the 'case 4:'
>
> if (!IS_ENABLED(CONFIG_64))
>         break;
>
> That's less uggly than adding two #ifdef/#endif

So you mean changing:

#ifdef __powerpc64__
  case 4:
    if (!cpu_has_feature(CPU_FTR_ARCH_300))
      return -1;

into:

  case 4:
    if (!IS_ENABLED(CONFIG_PPC64))
      break;
    if (!cpu_has_feature(CPU_FTR_ARCH_300))
      return -1;

So suddenly case label '4' becomes visible for ppc32, is that really
what you wanted ?

> Christophe
>
> >
> > Anyway I'll try your suggestion and post a v2.
> >
> >> Christophe
> >>
> >>>        unsigned long int imm;
> >>>        unsigned long int val, val2;
> >>>        unsigned int mb, me, sh;
> >>>