Re: [PATCH] powerpc: sstep: Mark variable `rc` as unused in function 'analyse_instr'

From: Mathieu Malaterre
Date: Wed Mar 13 2019 - 16:12:30 EST


On Tue, Mar 12, 2019 at 10:26 PM Christophe Leroy
<christophe.leroy@xxxxxx> wrote:
>
>
>
> Le 12/03/2019 Ã 22:12, Mathieu Malaterre a Ãcrit :
> > On Tue, Mar 12, 2019 at 9:56 PM Christophe Leroy
> > <christophe.leroy@xxxxxx> wrote:
> >>
> >>
> >>
> >> Le 12/03/2019 Ã 21:20, Mathieu Malaterre a Ãcrit :
> >>> 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@xxxxxxxxxx>
> >>> ---
> >>> 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;
> >>>