[Mesa-dev] [PATCH v2 3/3] util: use faster zlib's CRC32 implementaion

[Marek Olšák]

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Tue, Jan 9, 2018 at 11:58 PM, Grazvydas Ignotas <notasas at gmail.com> wrote:
> zlib provides a faster slice-by-4 CRC32 implementation than the
> traditional single byte lookup one used by mesa. As most supported
> platforms now link zlib unconditionally, we can easily use it.
>
> Improvement for a 1MB buffer (avg MB/s, n=100, zlib 1.2.8):
>
>   i5-6600K                    C2D E4500
> mesa zlib                    mesa zlib
>  443 1443 225% +/- 2.1%       403 1175 191% +/- 0.9%
>
> It has been verified the calculation results stay the same after this
> change.
>
> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
> ---
> v2: drop the size threshold check because size is unlikely to be that
> low of things mesa is typically hashing
>
>  src/util/crc32.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/src/util/crc32.c b/src/util/crc32.c
> index f2e01c6..9edd3e1 100644
> --- a/src/util/crc32.c
> +++ b/src/util/crc32.c
> @@ -31,10 +31,13 @@
>   *
>   * @author Jose Fonseca
>   */
>
>
> +#ifdef HAVE_ZLIB
> +#include <zlib.h>
> +#endif
>  #include "crc32.h"
>
>
>  static const uint32_t
>  util_crc32_table[256] = {
> @@ -112,10 +115,19 @@ uint32_t
>  util_hash_crc32(const void *data, size_t size)
>  {
>     const uint8_t *p = data;
>     uint32_t crc = 0xffffffff;
>
> +#ifdef HAVE_ZLIB
> +   /* zlib's uInt is always "unsigned int" while size_t can be 64bit.
> +    * Since 1.2.9 there's crc32_z that takes size_t, but use the more
> +    * available function to avoid build system complications.
> +    */
> +   if ((uInt)size == size)
> +      return ~crc32(0, data, size);
> +#endif
> +
>     while (size--)
>        crc = util_crc32_table[(crc ^ *p++) & 0xff] ^ (crc >> 8);
>
>     return crc;
>  }
> --
> 2.7.4
>
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