Re: [PATCH v4 08/10] util/bufferiszero: Simplify test_buffer_is_zero_next_accel

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

On 15/2/24 09:14, Richard Henderson wrote:
> Because the three alternatives are monotonic, we don't
> need to keep a couple of bitmasks, just identify the
> strongest alternative at startup.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   util/bufferiszero.c | 56 ++++++++++++++++++---------------------------
>   1 file changed, 22 insertions(+), 34 deletions(-)

enum {
   ACCEL_DEFAULT,
   ACCEL_SSE2,
   ACCEL_AVX2,
};

> +static biz_accel_fn const accel_table[] = {

   [ACCEL_DEFAULT] =

> +    buffer_is_zero_int_ge256,

   [ACCEL_SSE2] =

> +    buffer_zero_sse2,
>   #ifdef CONFIG_AVX2_OPT

   [ACCEL_AVX2] =

> +    buffer_zero_avx2,
>   #endif


> +static unsigned accel_index;
>   
>   static void __attribute__((constructor)) init_accel(void)
>   {
> -    used_accel = select_accel_cpuinfo(cpuinfo_init());
> +    unsigned info = cpuinfo_init();
> +    unsigned index = (info & CPUINFO_SSE2 ? 1 : 0);

   ... ? ACCEL_SSE2 : ACCEL_DEFAULT;

> +
> +#ifdef CONFIG_AVX2_OPT
> +    if (info & CPUINFO_AVX2) {
> +        index = 2;

   ... = ACCEL_AVX2

> +    }
> +#endif
> +
> +    accel_index = index;
> +    buffer_is_zero_accel = accel_table[index];
>   }
Preferably introducing accel enum:
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>