Re: [PATCH v2] hash: fix thash gfni implementation

[David Marchand <david.marchand@redhat.com>]

On Fri, Nov 12, 2021 at 3:17 PM Vladimir Medvedkin
<vladimir.medvedkin@intel.com> wrote:
>
> 1. This patch replaces _mm512_set_epi8 with _mm512_set_epi32
> due to the lack of support by some compilers.

Ok, it was the initial report from Lance.

> 2. This patch checks if AVX512F is supported along with GFNI.
> This is done if the code is built on a platform that supports GFNI,
> but does not support AVX512.

Ok.

> 3. Also this patch fixes compilation problems on 32bit arch due to
> lack of support for _mm_extract_epi64() by implementing XOR folding
> with _mm_extract_epi32() on 32-bit arch.

This code is under a #if defined(__GFNI__) && defined(__AVX512F__).

Does such a 32 bits processor exist, that supports AVX512 and GFNI?


>
> Fixes: 4fd8c4cb0de1 ("hash: add new Toeplitz hash implementation")
> Cc: vladimir.medvedkin@intel.com
>
> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> Acked-by: Lance Richardson <lance.richardson@broadcom.com>
> Acked-by: Ji, Kai <kai.ji@intel.com>
> ---
>  lib/hash/rte_thash_x86_gfni.h | 44 ++++++++++++++++++++---------------
>  1 file changed, 25 insertions(+), 19 deletions(-)
>
> diff --git a/lib/hash/rte_thash_x86_gfni.h b/lib/hash/rte_thash_x86_gfni.h
> index c2889c3734..987dec4988 100644
> --- a/lib/hash/rte_thash_x86_gfni.h
> +++ b/lib/hash/rte_thash_x86_gfni.h
> @@ -18,7 +18,7 @@
>  extern "C" {
>  #endif
>
> -#ifdef __GFNI__
> +#if defined(__GFNI__) && defined(__AVX512F__)

Please update #endif comments accordingly, or remove invalid/obsolete
comment about _GFNI_.


>  #define RTE_THASH_GFNI_DEFINED
>
>  #define RTE_THASH_FIRST_ITER_MSK       0x0f0f0f0f0f0e0c08
> @@ -33,7 +33,6 @@ __rte_thash_xor_reduce(__m512i xor_acc, uint32_t *val_1, uint32_t *val_2)
>  {
>         __m256i tmp_256_1, tmp_256_2;
>         __m128i tmp128_1, tmp128_2;
> -       uint64_t tmp_1, tmp_2;
>
>         tmp_256_1 = _mm512_castsi512_si256(xor_acc);
>         tmp_256_2 = _mm512_extracti32x8_epi32(xor_acc, 1);
> @@ -43,12 +42,24 @@ __rte_thash_xor_reduce(__m512i xor_acc, uint32_t *val_1, uint32_t *val_2)
>         tmp128_2 = _mm256_extracti32x4_epi32(tmp_256_1, 1);
>         tmp128_1 = _mm_xor_si128(tmp128_1, tmp128_2);
>
> +#ifdef RTE_ARCH_X86_64
> +       uint64_t tmp_1, tmp_2;
>         tmp_1 = _mm_extract_epi64(tmp128_1, 0);
>         tmp_2 = _mm_extract_epi64(tmp128_1, 1);
>         tmp_1 ^= tmp_2;
>
>         *val_1 = (uint32_t)tmp_1;
>         *val_2 = (uint32_t)(tmp_1 >> 32);
> +#else
> +       uint32_t tmp_1, tmp_2;
> +       tmp_1 = _mm_extract_epi32(tmp128_1, 0);
> +       tmp_2 = _mm_extract_epi32(tmp128_1, 1);
> +       tmp_1 ^= _mm_extract_epi32(tmp128_1, 2);
> +       tmp_2 ^= _mm_extract_epi32(tmp128_1, 3);
> +
> +       *val_1 = tmp_1;
> +       *val_2 = tmp_2;
> +#endif
>  }
>
>  __rte_internal
> @@ -56,23 +67,18 @@ static inline __m512i
>  __rte_thash_gfni(const uint64_t *mtrx, const uint8_t *tuple,
>         const uint8_t *secondary_tuple, int len)
>  {
> -       __m512i permute_idx = _mm512_set_epi8(7, 6, 5, 4, 7, 6, 5, 4,
> -                                               6, 5, 4, 3, 6, 5, 4, 3,
> -                                               5, 4, 3, 2, 5, 4, 3, 2,
> -                                               4, 3, 2, 1, 4, 3, 2, 1,
> -                                               3, 2, 1, 0, 3, 2, 1, 0,
> -                                               2, 1, 0, -1, 2, 1, 0, -1,
> -                                               1, 0, -1, -2, 1, 0, -1, -2,
> -                                               0, -1, -2, -3, 0, -1, -2, -3);
> -
> -       const __m512i rewind_idx = _mm512_set_epi8(0, 0, 0, 0, 0, 0, 0, 0,
> -                                               0, 0, 0, 0, 0, 0, 0, 0,
> -                                               0, 0, 0, 0, 0, 0, 0, 0,
> -                                               0, 0, 0, 0, 0, 0, 0, 0,
> -                                               0, 0, 0, 0, 0, 0, 0, 0,
> -                                               0, 0, 0, 59, 0, 0, 0, 59,
> -                                               0, 0, 59, 58, 0, 0, 59, 58,
> -                                               0, 59, 58, 57, 0, 59, 58, 57);
> +       __m512i permute_idx = _mm512_set_epi32(0x7060504, 0x7060504,

Nit: it is easier to read fully expanded 32 bits values, like
0x07060504 instead of 0x7060504
Etc...


> +                                               0x6050403, 0x6050403,
> +                                               0x5040302, 0x5040302,
> +                                               0x4030201, 0x4030201,
> +                                               0x3020100, 0x3020100,
> +                                               0x20100FF, 0x20100FF,
> +                                               0x100FFFE, 0x100FFFE,
> +                                               0xFFFEFD, 0xFFFEFD);
> +       const __m512i rewind_idx = _mm512_set_epi32(0, 0, 0, 0, 0, 0, 0, 0,
> +                                                       0, 0, 0x3B, 0x3B,
> +                                                       0x3B3A, 0x3B3A,
> +                                                       0x3B3A39, 0x3B3A39);
>         const __mmask64 rewind_mask = RTE_THASH_REWIND_MSK;
>         const __m512i shift_8 = _mm512_set1_epi8(8);
>         __m512i xor_acc = _mm512_setzero_si512();
> --
> 2.25.1
>


-- 
David Marchand