Re: [PATCH 03/10] target/i386: Avoid using floatx80_infinity global const

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 17/2/25 13:50, Peter Maydell wrote:
> The global const floatx80_infinity is (unlike all the other
> float*_infinity values) target-specific, because whether the explicit
> Integer bit is set or not varies between m68k and i386.  We want to
> be able to compile softfloat once for multiple targets, so we can't
> continue to use a single global whose value needs to be different
> between targets.
> 
> Replace the direct uses of floatx80_infinity in target/i386 with
> calls to the new floatx80_default_inf() function.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/i386/tcg/fpu_helper.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)


> @@ -2358,9 +2358,8 @@ void helper_fscale(CPUX86State *env)
>                   float_raise(float_flag_invalid, &env->fp_status);
>                   ST0 = floatx80_default_nan(&env->fp_status);
>               } else {
> -                ST0 = (floatx80_is_neg(ST0) ?
> -                       floatx80_chs(floatx80_infinity) :
> -                       floatx80_infinity);
> +                ST0 = floatx80_default_inf(floatx80_is_neg(ST0),
> +                                           &env->fp_status);

Which expand to:

{
   .low = floatx80_default_inf_int_bit_is_zero ? 0 : (1ULL << 63),
   .high = (((uint16_t)zSign) << 15) + 0x7fff
}

Effectively equivalent of toggling the sign with floatx80_chs
(the floatx80_chs removal was not obvious, worth mentioning?).

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Review note, as softfloat API methods names are verbose,
float*_chs() could be renamed as _change_sign().

Regards,

Phil.