Re: [PATCH 45/76] target/arm: Implement FPCR.AH semantics for scalar FMIN/FMAX

[Richard Henderson]

On 1/24/25 08:28, Peter Maydell wrote:
> diff --git a/target/arm/tcg/helper-a64.c b/target/arm/tcg/helper-a64.c
> index 05036089dd7..406d76e1129 100644
> --- a/target/arm/tcg/helper-a64.c
> +++ b/target/arm/tcg/helper-a64.c
> @@ -399,6 +399,42 @@ float32 HELPER(fcvtx_f64_to_f32)(float64 a, float_status 
> *fpst)
>       return r;
>   }
>   
> +/*
> + * AH=1 min/max have some odd special cases:
> + * comparing two zeroes (even of different sign), (NaN, anything),
> + * or (anything, NaN) should return the second argument (possibly
> + * squashed to zero).
> + * Also, denormal outputs are not squashed to zero regardless of FZ or FZ16.
> + */
> +#define AH_MINMAX_HELPER(NAME, CTYPE, FLOATTYPE, MINMAX)                \
> +    CTYPE HELPER(NAME)(CTYPE a, CTYPE b, float_status *fpst)            \
> +    {                                                                   \
> +        bool save;                                                      \
> +        CTYPE r;                                                        \
> +        a = FLOATTYPE ## _squash_input_denormal(a, fpst);               \
> +        b = FLOATTYPE ## _squash_input_denormal(b, fpst);               \
> +        if (FLOATTYPE ## _is_zero(a) && FLOATTYPE ## _is_zero(b)) {     \

The comment says "even of different sign", the pseudocode explicitly checks different 
sign.  But of course if they're the same sign a and b are indistinguishable.  Perhaps 
slightly different wording?

Anyway,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~