Re: [PATCH 29/72] softfloat: Move pick_nan to softfloat-parts.c.inc

[David Hildenbrand <david@redhat.com>]

On 08.05.21 03:47, Richard Henderson wrote:
> At the same time, convert to pointers, rename to parts$N_pick_nan
> and define a macro for parts_pick_nan using QEMU_GENERIC.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   fpu/softfloat.c           | 62 ++++++++++++++++++++++-----------------
>   fpu/softfloat-parts.c.inc | 25 ++++++++++++++++
>   2 files changed, 60 insertions(+), 27 deletions(-)
> 
> diff --git a/fpu/softfloat.c b/fpu/softfloat.c
> index 5b26696078..77efaedeaa 100644
> --- a/fpu/softfloat.c
> +++ b/fpu/softfloat.c
> @@ -713,10 +713,39 @@ static void parts128_return_nan(FloatParts128 *a, float_status *s);
>   
>   #define parts_return_nan(P, S)     PARTS_GENERIC_64_128(return_nan, P)(P, S)
>   
> +static FloatParts64 *parts64_pick_nan(FloatParts64 *a, FloatParts64 *b,
> +                                      float_status *s);
> +static FloatParts128 *parts128_pick_nan(FloatParts128 *a, FloatParts128 *b,
> +                                        float_status *s);
> +
> +#define parts_pick_nan(A, B, S)    PARTS_GENERIC_64_128(pick_nan, A)(A, B, S)
> +
>   /*
>    * Helper functions for softfloat-parts.c.inc, per-size operations.
>    */
>   
> +#define FRAC_GENERIC_64_128(NAME, P) \
> +    QEMU_GENERIC(P, (FloatParts128 *, frac128_##NAME), frac64_##NAME)
> +
> +static int frac64_cmp(FloatParts64 *a, FloatParts64 *b)
> +{
> +    return a->frac == b->frac ? 0 : a->frac < b->frac ? -1 : 1;
> +}
> +
> +static int frac128_cmp(FloatParts128 *a, FloatParts128 *b)
> +{
> +    uint64_t ta = a->frac_hi, tb = b->frac_hi;
> +    if (ta == tb) {
> +        ta = a->frac_lo, tb = b->frac_lo;
> +        if (ta == tb) {
> +            return 0;
> +        }
> +    }
> +    return ta < tb ? -1 : 1;
> +}
> +
> +#define frac_cmp(A, B)  FRAC_GENERIC_64_128(cmp, A)(A, B)
> +
>   static void frac128_shl(FloatParts128 *a, int c)
>   {
>       shift128Left(a->frac_hi, a->frac_lo, c, &a->frac_hi, &a->frac_lo);
> @@ -918,27 +947,6 @@ static FloatParts64 round_canonical(FloatParts64 p, float_status *s,
>       return p;
>   }
>   
> -static FloatParts64 pick_nan(FloatParts64 a, FloatParts64 b, float_status *s)
> -{
> -    if (is_snan(a.cls) || is_snan(b.cls)) {
> -        float_raise(float_flag_invalid, s);
> -    }
> -
> -    if (s->default_nan_mode) {
> -        parts_default_nan(&a, s);
> -    } else {
> -        if (pickNaN(a.cls, b.cls,
> -                    a.frac > b.frac ||
> -                    (a.frac == b.frac && a.sign < b.sign), s)) {
> -            a = b;
> -        }
> -        if (is_snan(a.cls)) {
> -            parts_silence_nan(&a, s);
> -        }
> -    }
> -    return a;
> -}
> -
>   static FloatParts64 pick_nan_muladd(FloatParts64 a, FloatParts64 b, FloatParts64 c,
>                                     bool inf_zero, float_status *s)
>   {
> @@ -1106,7 +1114,7 @@ static FloatParts64 addsub_floats(FloatParts64 a, FloatParts64 b, bool subtract,
>               return a;
>           }
>           if (is_nan(a.cls) || is_nan(b.cls)) {
> -            return pick_nan(a, b, s);
> +            return *parts_pick_nan(&a, &b, s);
>           }
>           if (a.cls == float_class_inf) {
>               if (b.cls == float_class_inf) {
> @@ -1144,7 +1152,7 @@ static FloatParts64 addsub_floats(FloatParts64 a, FloatParts64 b, bool subtract,
>               return a;
>           }
>           if (is_nan(a.cls) || is_nan(b.cls)) {
> -            return pick_nan(a, b, s);
> +            return *parts_pick_nan(&a, &b, s);
>           }
>           if (a.cls == float_class_inf || b.cls == float_class_zero) {
>               return a;
> @@ -1360,7 +1368,7 @@ static FloatParts64 mul_floats(FloatParts64 a, FloatParts64 b, float_status *s)
>       }
>       /* handle all the NaN cases */
>       if (is_nan(a.cls) || is_nan(b.cls)) {
> -        return pick_nan(a, b, s);
> +        return *parts_pick_nan(&a, &b, s);
>       }
>       /* Inf * Zero == NaN */
>       if ((a.cls == float_class_inf && b.cls == float_class_zero) ||
> @@ -1887,7 +1895,7 @@ static FloatParts64 div_floats(FloatParts64 a, FloatParts64 b, float_status *s)
>       }
>       /* handle all the NaN cases */
>       if (is_nan(a.cls) || is_nan(b.cls)) {
> -        return pick_nan(a, b, s);
> +        return *parts_pick_nan(&a, &b, s);
>       }
>       /* 0/0 or Inf/Inf */
>       if (a.cls == b.cls
> @@ -3295,14 +3303,14 @@ static FloatParts64 minmax_floats(FloatParts64 a, FloatParts64 b, bool ismin,
>                * the invalid exception is raised.
>                */
>               if (is_snan(a.cls) || is_snan(b.cls)) {
> -                return pick_nan(a, b, s);
> +                return *parts_pick_nan(&a, &b, s);
>               } else if (is_nan(a.cls) && !is_nan(b.cls)) {
>                   return b;
>               } else if (is_nan(b.cls) && !is_nan(a.cls)) {
>                   return a;
>               }
>           }
> -        return pick_nan(a, b, s);
> +        return *parts_pick_nan(&a, &b, s);
>       } else {
>           int a_exp, b_exp;
>   
> diff --git a/fpu/softfloat-parts.c.inc b/fpu/softfloat-parts.c.inc
> index 2a3075d6fe..11a71650f7 100644
> --- a/fpu/softfloat-parts.c.inc
> +++ b/fpu/softfloat-parts.c.inc
> @@ -35,3 +35,28 @@ static void partsN(return_nan)(FloatPartsN *a, float_status *s)
>           g_assert_not_reached();
>       }
>   }
> +
> +static FloatPartsN *partsN(pick_nan)(FloatPartsN *a, FloatPartsN *b,
> +                                     float_status *s)
> +{
> +    if (is_snan(a->cls) || is_snan(b->cls)) {
> +        float_raise(float_flag_invalid, s);
> +    }
> +
> +    if (s->default_nan_mode) {
> +        parts_default_nan(a, s);
> +    } else {
> +        int cmp = frac_cmp(a, b);
> +        if (cmp == 0) {
> +            cmp = a->sign < b->sign;
> +        }
> +
> +        if (pickNaN(a->cls, b->cls, cmp > 0, s)) {
> +            a = b;
> +        }
> +        if (is_snan(a->cls)) {
> +            parts_silence_nan(a, s);
> +        }
> +    }
> +    return a;
> +}
> 

I find the "*parts_pick_nan(&a, &b, s);" part a little ugly to read, but 
as long as this function isn't inline there isn't much the compiler 
could optimize when passing by value instead, so

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb