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

[Aleksandar Markovic]

> 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 <ma...@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;
                }

Regards,
Aleksandar