Re: [dpdk-dev] [PATCH v4 1/8] eal: introduce zmm type for AVX 512-bit

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

On Wed, Jul 8, 2020 at 10:17 PM Vladimir Medvedkin
<vladimir.medvedkin@intel.com> wrote:
>
> New data type to manipulate 512 bit AVX values.

The title mentions a "zmm" type that is not added by this patch.

Maybe instead, "eal/x86: introduce AVX 512-bit type"


>
> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---
>  lib/librte_eal/x86/include/rte_vect.h | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/lib/librte_eal/x86/include/rte_vect.h b/lib/librte_eal/x86/include/rte_vect.h
> index df5a60762..ae59126bc 100644
> --- a/lib/librte_eal/x86/include/rte_vect.h
> +++ b/lib/librte_eal/x86/include/rte_vect.h
> @@ -13,6 +13,7 @@
>
>  #include <stdint.h>
>  #include <rte_config.h>
> +#include <rte_common.h>
>  #include "generic/rte_vect.h"
>
>  #if (defined(__ICC) || \
> @@ -90,6 +91,26 @@ __extension__ ({                 \
>  })
>  #endif /* (defined(__ICC) && __ICC < 1210) */
>
> +#ifdef __AVX512F__
> +
> +typedef __m512i __x86_zmm_t;

We don't need this interim type, using the native __m512 is enough afaics.

Looking at the whole applied series:
$ git grep -lw __x86_zmm_t
lib/librte_eal/x86/include/rte_vect.h


> +
> +#define        ZMM_SIZE        (sizeof(__x86_zmm_t))
> +#define        ZMM_MASK        (ZMM_SIZE - 1)

Macros in a public header need a RTE_ prefix + this is x86 specific,
then RTE_X86_.

Looking at the whole applied series:
$ git grep -lw ZMM_SIZE
lib/librte_eal/x86/include/rte_vect.h
$ git grep -lw ZMM_MASK
lib/librte_eal/x86/include/rte_vect.h

So I wonder if we need to export it or we can instead just #undef
after the struct definition.


> +
> +typedef union __rte_x86_zmm  {
> +       __x86_zmm_t      z;
> +       ymm_t    y[ZMM_SIZE / sizeof(ymm_t)];
> +       xmm_t    x[ZMM_SIZE / sizeof(xmm_t)];
> +       uint8_t  u8[ZMM_SIZE / sizeof(uint8_t)];
> +       uint16_t u16[ZMM_SIZE / sizeof(uint16_t)];
> +       uint32_t u32[ZMM_SIZE / sizeof(uint32_t)];
> +       uint64_t u64[ZMM_SIZE / sizeof(uint64_t)];
> +       double   pd[ZMM_SIZE / sizeof(double)];
> +} __rte_aligned(ZMM_SIZE) __rte_x86_zmm_t;

I don't understand this forced alignment statement.
Would not natural alignment be enough, since all fields in this union
have the same size?


-- 
David Marchand