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From: Jeff King <peff@peff.net>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Duy Nguyen" <pclouds@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Git Mailing List" <git@vger.kernel.org>
Subject: Re: [ANNOUNCE] Git v2.19.0-rc0
Date: Wed, 22 Aug 2018 12:59:23 -0400	[thread overview]
Message-ID: <20180822165923.GA14878@sigill.intra.peff.net> (raw)
In-Reply-To: <7ea416cf-b043-1274-e161-85a8780b8e1c@gmail.com>

On Wed, Aug 22, 2018 at 12:49:34PM -0400, Derrick Stolee wrote:

> > Yes, that was what I meant. We actually did switch to that hand-rolled
> > loop, but later we went back to memcmp in 0b006014c8 (hashcmp: use
> > memcmp instead of open-coded loop, 2017-08-09).
> 
> Looking at that commit, I'm surprised the old logic was just a for
> loop, instead of a word-based approach, such as the following:
> [...]
> +struct object_id_20 {
> +       uint64_t data0;
> +       uint64_t data1;
> +       uint32_t data2;
> +};
> +
>  static inline int hashcmp(const unsigned char *sha1, const unsigned char
> *sha2)
>  {
> -       return memcmp(sha1, sha2, the_hash_algo->rawsz);
> +       if (the_hash_algo->rawsz == 20) {
> +               struct object_id_20 *obj1 = (struct object_id_20 *)sha1;
> +               struct object_id_20 *obj2 = (struct object_id_20 *)sha2;

I wonder if you're potentially running afoul of alignment requirements
here.

-Peff

  parent reply	other threads:[~2018-08-22 16:59 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-20 22:13 [ANNOUNCE] Git v2.19.0-rc0 Junio C Hamano
2018-08-20 22:41 ` Stefan Beller
2018-08-20 23:39   ` Jonathan Nieder
2018-08-21  0:27     ` Jonathan Nieder
2018-08-21  0:46       ` Stefan Beller
2018-08-21 20:41 ` Derrick Stolee
2018-08-21 21:29   ` Jeff King
2018-08-22  0:48     ` brian m. carlson
2018-08-22  3:03       ` Jeff King
2018-08-22  3:36         ` Jeff King
2018-08-22 11:11           ` Derrick Stolee
2018-08-22  5:36         ` brian m. carlson
2018-08-22  6:07           ` Jeff King
2018-08-22  7:39             ` Ævar Arnfjörð Bjarmason
2018-08-22 11:14               ` Derrick Stolee
2018-08-22 15:17                 ` Jeff King
2018-08-22 16:08                   ` Duy Nguyen
2018-08-22 16:14                     ` Duy Nguyen
2018-08-22 16:26                       ` Jeff King
2018-08-22 16:49                         ` Derrick Stolee
2018-08-22 16:58                           ` Duy Nguyen
2018-08-22 17:04                             ` Derrick Stolee
2018-08-22 16:59                           ` Jeff King [this message]
2018-08-22 17:02                             ` Junio C Hamano
2018-08-22 15:14               ` Jeff King
2018-08-22 14:28           ` Derrick Stolee
2018-08-22 15:24             ` Jeff King
2018-08-22 12:42         ` Paul Smith
2018-08-22 15:23           ` Jeff King
2018-08-23  1:23             ` Jonathan Nieder
2018-08-23  2:16               ` Jeff King
2018-08-23  2:27                 ` Jonathan Nieder
2018-08-23  5:02                   ` Jeff King
2018-08-23  5:09                     ` brian m. carlson
2018-08-23  5:10                     ` Jonathan Nieder
2018-08-23 13:20                     ` Junio C Hamano
2018-08-23 16:31                       ` wide t/perf output, was " Jeff King
2018-08-23  3:47                 ` brian m. carlson
2018-08-23  5:04                   ` Jeff King
2018-08-23 10:26                     ` Derrick Stolee
2018-08-23 13:16                       ` Junio C Hamano
2018-08-23 16:14                       ` Jeff King
2018-08-23 23:30                         ` Jacob Keller
2018-08-23 23:40                           ` Jeff King
2018-08-24  0:06                             ` Jeff King
2018-08-24  0:16                               ` Jeff King
2018-08-24  2:48                                 ` Jacob Keller
2018-08-24  2:59                                   ` Jeff King
2018-08-24  6:45                                     ` Jeff King
2018-08-24 11:04                                       ` Derrick Stolee
2018-08-27 19:36                                     ` Junio C Hamano
2018-08-23 18:53                       ` Jeff King
2018-08-23 20:59                         ` Derrick Stolee
2018-08-24  6:56                           ` Jeff King
2018-08-24  7:57                             ` Ævar Arnfjörð Bjarmason
2018-08-24 16:45                           ` Derrick Stolee
2018-08-25  8:26                             ` Jeff King
2018-09-02 18:53                       ` Kaartic Sivaraam

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