Re: [PATCH v2 05/27] util/bufferiszero: Use i386 host/cpuinfo.h

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Use cpuinfo_init() during init_accel(), and the variable cpuinfo
> during test_buffer_is_zero_next_accel().  Adjust the logic that
> cycles through the set of accelerators for testing.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  util/bufferiszero.c | 126 ++++++++++++++++----------------------------
>  1 file changed, 45 insertions(+), 81 deletions(-)
>
> diff --git a/util/bufferiszero.c b/util/bufferiszero.c
> index 1886bc5ba4..d3c14320ef 100644
> --- a/util/bufferiszero.c
> +++ b/util/bufferiszero.c
<snip>
> +static unsigned __attribute__((noinline))
> +select_accel_cpuinfo(unsigned info)
>  {
> -    bool (*fn)(const void *, size_t) = buffer_zero_int;
> -    if (cache & CACHE_SSE2) {
> -        fn = buffer_zero_sse2;
> -        length_to_accel = 64;
> -    }
> -#ifdef CONFIG_AVX2_OPT
> -    if (cache & CACHE_SSE4) {
> -        fn = buffer_zero_sse4;
> -        length_to_accel = 64;
> -    }
> -    if (cache & CACHE_AVX2) {
> -        fn = buffer_zero_avx2;
> -        length_to_accel = 128;
> -    }
> -#endif
> +    static const struct {
> +        unsigned bit;
> +        unsigned len;
> +        bool (*fn)(const void *, size_t);
> +    } all[] = {
>  #ifdef CONFIG_AVX512F_OPT
> -    if (cache & CACHE_AVX512F) {
> -        fn = buffer_zero_avx512;
> -        length_to_accel = 256;
> -    }
> +        { CPUINFO_AVX512F, 256, buffer_zero_avx512 },
>  #endif
> -    buffer_accel = fn;
> +#ifdef CONFIG_AVX2_OPT
> +        { CPUINFO_AVX2,    128, buffer_zero_avx2 },
> +        { CPUINFO_SSE4,     64, buffer_zero_sse4 },
> +#endif
> +        { CPUINFO_SSE2,     64, buffer_zero_sse2 },
> +        { CPUINFO_ALWAYS,    0, buffer_zero_int },
> +    };
> +

Arguably we could have a brief one liner saying table in order of
preference.

Anyway:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro