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From: "H. Peter Anvin" <hpa@zytor.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Juri Lelli <juri.lelli@gmail.com>
Subject: Re: [RFC][PATCH 0/3] gcc work-around and math128
Date: Tue, 24 Apr 2012 10:22:28 -0700	[thread overview]
Message-ID: <4F96E154.2060100@zytor.com> (raw)
In-Reply-To: <20120424161039.293018424@chello.nl>

On 04/24/2012 09:10 AM, Peter Zijlstra wrote:
> 
> So far its just mult, add and cmp for u128, no divisions quite yet. I realize
> that on 32bit archs mult_u128 will result in like 8 multiplication
> instructions that's still nowhere near the most expensive thing ever.
> 

Please add shifts, at the very least.

	-hpa


  parent reply	other threads:[~2012-04-24 17:22 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-24 16:10 [RFC][PATCH 0/3] gcc work-around and math128 Peter Zijlstra
2012-04-24 16:10 ` [RFC][PATCH 1/3] kernel,sched,time: Clean up gcc work-arounds Peter Zijlstra
2012-04-24 19:39   ` Linus Torvalds
2012-04-25  0:14   ` Stephen Rothwell
2012-04-24 16:10 ` [RFC][PATCH 2/3] math128: Introduce {mult,add,cmp}_u128 Peter Zijlstra
2012-04-24 19:37   ` Linus Torvalds
2012-04-24 19:43     ` Peter Zijlstra
2012-04-24 20:12     ` Måns Rullgård
2012-04-24 21:54     ` Peter Zijlstra
2012-04-25  0:09       ` H. Peter Anvin
2012-04-25  1:46       ` Linus Torvalds
2012-04-25  8:35         ` Peter Zijlstra
2012-04-25 10:13         ` Peter Zijlstra
2012-04-25  0:23   ` Stephen Rothwell
2012-04-25  8:11     ` Peter Zijlstra
2012-04-25 11:23       ` Geert Uytterhoeven
2012-04-25 11:58         ` Peter Zijlstra
2012-04-25 14:35           ` Geert Uytterhoeven
2012-04-25 15:09             ` Peter Zijlstra
2012-04-24 16:10 ` [RFC][PATCH 3/3] math128, x86_64: Implement {mult,add}_u128 in 64bit asm Peter Zijlstra
2012-04-24 16:34   ` H. Peter Anvin
2012-04-24 16:36     ` Peter Zijlstra
2012-04-24 17:17       ` H. Peter Anvin
2012-04-24 17:19         ` Peter Zijlstra
2012-04-24 17:20           ` H. Peter Anvin
2012-04-24 22:00             ` Peter Zijlstra
2012-04-24 22:03               ` H. Peter Anvin
2012-04-24 17:22 ` H. Peter Anvin [this message]
2012-04-24 17:27   ` [RFC][PATCH 0/3] gcc work-around and math128 H. Peter Anvin
2012-04-24 21:15 ` Andy Lutomirski
2012-04-24 21:18   ` Linus Torvalds
2012-04-24 21:32   ` Peter Zijlstra
2012-04-24 21:35     ` Andy Lutomirski
2012-04-24 21:51       ` Peter Zijlstra

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