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SubjectRe: [PATCH 2/2] MIPS: math-emu: Declare ys variable as possibly unused
Aleksandar,

On Tue, Dec 26, 2017 at 4:12 PM, Aleksandar Markovic
<Aleksandar.Markovic@mips.com> wrote:
>> Fix non-fatal warning:
>>
>> arch/mips/math-emu/sp_fdp.c: In function ‘ieee754sp_fdp’:
>> arch/mips/math-emu/ieee754int.h:60:31: warning: variable ‘ys’ set but not used [-Wunused-but-set-variable]
>> unsigned int ym; int ye; int ys; int yc
>> ^
>> arch/mips/math-emu/sp_fdp.c:37:2: note: in expansion of macro ‘COMPYSP’
>> COMPYSP;
>> ^~~~~~~
>>
>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>> ---
>> arch/mips/math-emu/ieee754int.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/mips/math-emu/ieee754int.h b/arch/mips/math-emu/ieee754int.h
>> index 06ac0e2ac7ac..cb8f04cd24bf 100644
>> --- a/arch/mips/math-emu/ieee754int.h
>> +++ b/arch/mips/math-emu/ieee754int.h
>> @@ -57,7 +57,7 @@ static inline int ieee754_class_nan(int xc)
>> unsigned int xm; int xe; int xs __maybe_unused; int xc
>>
>> #define COMPYSP \
>> - unsigned int ym; int ye; int ys; int yc
>> + unsigned int ym; int ye; int ys __maybe_unused; int yc
>>
>> #define COMPZSP \
>> unsigned int zm; int ze; int zs; int zc
>
> This will silence the warning, but will do it for all future cases of unused
> ys too - in other words, it may well silence even useful, valid warnings.
> Also, this introduces an inconsistency among COMPXSP, COMPYSP, and COMPZSP
> macros.
>
> A better solution would be to reduce the scope of ys, so that it is always
> used, if declared. Instead of this code segment (in arch/mips/math-emu/sp_fdp.c):
>
> union ieee754sp ieee754sp_fdp(union ieee754dp x)
> {
> union ieee754sp y;
> u32 rm;
>
> COMPXDP;
> COMPYSP;
>
> EXPLODEXDP;
>
> ieee754_clearcx();
>
> FLUSHXDP;
>
> switch (xc) {
> case IEEE754_CLASS_SNAN:
> x = ieee754dp_nanxcpt(x);
> EXPLODEXDP;
> /* Fall through. */
> case IEEE754_CLASS_QNAN:
> y = ieee754sp_nan_fdp(xs, xm);
> if (!ieee754_csr.nan2008) {
> EXPLODEYSP;
> if (!ieee754_class_nan(yc))
> y = ieee754sp_indef();
> }
> return y;
>
>
> ... should be the following: (COMPYSP is moved to a smaller code block)
>
> union ieee754sp ieee754sp_fdp(union ieee754dp x)
> {
> union ieee754sp y;
> u32 rm;
>
> COMPXDP;
>
> EXPLODEXDP;
>
> ieee754_clearcx();
>
> FLUSHXDP;
>
> switch (xc) {
> case IEEE754_CLASS_SNAN:
> x = ieee754dp_nanxcpt(x);
> EXPLODEXDP;
> /* Fall through. */
> case IEEE754_CLASS_QNAN:
> {
> COMPYSP;
>
> y = ieee754sp_nan_fdp(xs, xm);
> if (!ieee754_csr.nan2008) {
> EXPLODEYSP;
> if (!ieee754_class_nan(yc))
> y = ieee754sp_indef();
> }
> return y;
> }
>


Thanks for the suggestion. However the sign bit is still not used, so
the warning is still there. Just for clarity did you see that:

#define COMPXSP \
unsigned int xm; int xe; int xs __maybe_unused; int xc

I'll try to give it some more thoughts, and come up with something
hopefully working.

-M

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