From: Linus Torvalds <torvalds@linux-foundation.org>
To: Artur Skawina <art.08.09@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: [PATCH 0/7] block-sha1: improved SHA1 hashing
Date: Thu, 6 Aug 2009 15:33:45 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.01.0908061531310.3390@localhost.localdomain> (raw)
In-Reply-To: <alpine.LFD.2.01.0908061502570.3390@localhost.localdomain>
On Thu, 6 Aug 2009, Linus Torvalds wrote:
>
> Anyway, on P4 I think you have two double-speed integer issue ports (ie
> max four ops per cycle), but only one of them takes a rotate, and only in
> the first half of the cycle (ie just one shift per cycle).
>
> And afaik, that is actually the _improved_ state in Prescott. The older
> P4's didn't have a full shifter unit at all, iirc: shifts were "complex
> instructions" in Northwood and weren't even single-clock.
Yeah, verified. Google for
northwood "barrel shifter"
and you'll find a lot of it.
Basically, older P4's will I think shift one bit at a time. So while even
Prescott is relatively weak in the shifter department, pre-prescott
(Willamette and Northwood) are _really_ weak. If your P4 is one of those,
you really shouldn't use it to decide on optimizations.
Linus
next prev parent reply other threads:[~2009-08-06 22:34 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-06 15:13 [PATCH 0/7] block-sha1: improved SHA1 hashing Linus Torvalds
2009-08-06 15:15 ` [PATCH 1/7] block-sha1: add new optimized C 'block-sha1' routines Linus Torvalds
2009-08-06 15:16 ` [PATCH 2/7] block-sha1: try to use rol/ror appropriately Linus Torvalds
2009-08-06 15:18 ` [PATCH 3/7] block-sha1: make the 'ntohl()' part of the first SHA1 loop Linus Torvalds
2009-08-06 15:20 ` [PATCH 4/7] block-sha1: re-use the temporary array as we calculate the SHA1 Linus Torvalds
2009-08-06 15:22 ` [PATCH 5/7] block-sha1: macroize the rounds a bit further Linus Torvalds
2009-08-06 15:24 ` [PATCH 6/7] block-sha1: Use '(B&C)+(D&(B^C))' instead of '(B&C)|(D&(B|C))' in round 3 Linus Torvalds
2009-08-06 15:25 ` [PATCH 7/7] block-sha1: get rid of redundant 'lenW' context Linus Torvalds
2009-08-06 18:25 ` [PATCH 2/7] block-sha1: try to use rol/ror appropriately Bert Wesarg
2009-08-06 17:22 ` [PATCH 0/7] block-sha1: improved SHA1 hashing Artur Skawina
2009-08-06 18:09 ` Linus Torvalds
2009-08-06 19:10 ` Artur Skawina
2009-08-06 19:41 ` Linus Torvalds
2009-08-06 20:08 ` Artur Skawina
2009-08-06 20:53 ` Linus Torvalds
2009-08-06 21:24 ` Linus Torvalds
2009-08-06 21:39 ` Artur Skawina
2009-08-06 21:52 ` Artur Skawina
2009-08-06 22:27 ` Linus Torvalds
2009-08-06 22:33 ` Linus Torvalds [this message]
2009-08-06 23:19 ` Artur Skawina
2009-08-06 23:42 ` Linus Torvalds
2009-08-06 22:55 ` Artur Skawina
2009-08-06 23:04 ` Linus Torvalds
2009-08-06 23:25 ` Linus Torvalds
2009-08-07 0:13 ` Linus Torvalds
2009-08-07 1:30 ` Artur Skawina
2009-08-07 1:55 ` Linus Torvalds
2009-08-07 0:53 ` Artur Skawina
2009-08-07 2:23 ` Linus Torvalds
2009-08-07 4:16 ` Artur Skawina
[not found] ` <alpine.LFD.2.01.0908071614310.3288@localhost.localdomain>
[not found] ` <4A7CBD28.6070306@gmail.com>
[not found] ` <4A7CBF47.9000903@gmail.com>
[not found] ` <alpine.LFD.2.01.0908071700290.3288@localhost.localdomain>
[not found] ` <4A7CC380.3070008@gmail.com>
2009-08-08 4:16 ` Linus Torvalds
2009-08-08 5:34 ` Artur Skawina
2009-08-08 17:10 ` Linus Torvalds
2009-08-08 18:12 ` Artur Skawina
2009-08-08 22:58 ` Artur Skawina
2009-08-08 23:36 ` Artur Skawina
-- strict thread matches above, loose matches on Subject: below --
2009-08-07 7:36 George Spelvin
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