From: "Woodhouse, David" <david.woodhouse@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Kim Phillips <kim.phillips@freescale.com>,
Russell King <linux@arm.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Daniel Santos <daniel.santos@pobox.com>,
David Rientjes <rientjes@google.com>,
Rusty Russell <rusty@rustcorp.com.au>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] arm: use built-in byte swap function
Date: Wed, 30 Jan 2013 10:22:15 +0000 [thread overview]
Message-ID: <1359541333.3529.186.camel@shinybook.infradead.org> (raw)
In-Reply-To: <20130129181046.GC25415@pd.tnic>
[-- Attachment #1: Type: text/plain, Size: 1370 bytes --]
On Tue, 2013-01-29 at 19:10 +0100, Borislav Petkov wrote:
> So, IMHO it sounds to me like we want to explicitly state for each arch
> separately that it is ok to use the __builtin_bswapXX things. This also
> takes care of the case where the compiler is doing something suboptimal
> by excluding the affected versions.
Well, if it really does end up being different for every architecture,
then that means I probably made the wrong decision when I chose to make
it "generic", and override the __arch_swabXX() macros. I could have just
pushed all the architectures to use the builtins in their __arch_swabXX
macros instead, as appropriate.
Let's see how many special cases we actually end up with, and perhaps
we'll end up switching that round. For now, let's just make ARM set
__HAVE_BUILTIN_BSWAPxx__ for the appropriate sizes in <asm/swab.h>,
according to whatever criteria it needs.
It's not entirely clear how much of a win it is on ARM anyway; we don't
have load-and-swap or store-and-swap instructions so there are only a
few added opportunities for optimisation that we get by letting the
compiler see what's going on.
--
Sent with MeeGo's ActiveSync support.
David Woodhouse Open Source Technology Centre
David.Woodhouse@intel.com Intel Corporation
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WARNING: multiple messages have this Message-ID (diff)
From: david.woodhouse@intel.com (Woodhouse, David)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC] arm: use built-in byte swap function
Date: Wed, 30 Jan 2013 10:22:15 +0000 [thread overview]
Message-ID: <1359541333.3529.186.camel@shinybook.infradead.org> (raw)
In-Reply-To: <20130129181046.GC25415@pd.tnic>
On Tue, 2013-01-29 at 19:10 +0100, Borislav Petkov wrote:
> So, IMHO it sounds to me like we want to explicitly state for each arch
> separately that it is ok to use the __builtin_bswapXX things. This also
> takes care of the case where the compiler is doing something suboptimal
> by excluding the affected versions.
Well, if it really does end up being different for every architecture,
then that means I probably made the wrong decision when I chose to make
it "generic", and override the __arch_swabXX() macros. I could have just
pushed all the architectures to use the builtins in their __arch_swabXX
macros instead, as appropriate.
Let's see how many special cases we actually end up with, and perhaps
we'll end up switching that round. For now, let's just make ARM set
__HAVE_BUILTIN_BSWAPxx__ for the appropriate sizes in <asm/swab.h>,
according to whatever criteria it needs.
It's not entirely clear how much of a win it is on ARM anyway; we don't
have load-and-swap or store-and-swap instructions so there are only a
few added opportunities for optimisation that we get by letting the
compiler see what's going on.
--
Sent with MeeGo's ActiveSync support.
David Woodhouse Open Source Technology Centre
David.Woodhouse at intel.com Intel Corporation
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next prev parent reply other threads:[~2013-01-30 10:22 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 1:30 [RFC] arm: use built-in byte swap function Kim Phillips
2013-01-29 1:30 ` Kim Phillips
2013-01-29 8:35 ` Borislav Petkov
2013-01-29 8:35 ` Borislav Petkov
2013-01-29 16:46 ` Woodhouse, David
2013-01-29 16:46 ` Woodhouse, David
2013-01-29 17:42 ` Borislav Petkov
2013-01-29 17:42 ` Borislav Petkov
2013-01-29 17:55 ` Woodhouse, David
2013-01-29 17:55 ` Woodhouse, David
2013-01-29 18:10 ` Borislav Petkov
2013-01-29 18:10 ` Borislav Petkov
2013-01-30 10:22 ` Woodhouse, David [this message]
2013-01-30 10:22 ` Woodhouse, David
2013-01-31 2:09 ` Kim Phillips
2013-01-31 2:09 ` Kim Phillips
2013-01-31 6:44 ` Borislav Petkov
2013-01-31 6:44 ` Borislav Petkov
2013-01-31 9:28 ` Russell King - ARM Linux
2013-01-31 9:28 ` Russell King - ARM Linux
2013-01-31 20:59 ` Kim Phillips
2013-01-31 20:59 ` Kim Phillips
2013-01-31 21:33 ` Borislav Petkov
2013-01-31 21:33 ` Borislav Petkov
2013-01-31 22:11 ` Woodhouse, David
2013-01-31 22:11 ` Woodhouse, David
2013-02-01 0:37 ` [PATCH v4] " Kim Phillips
2013-02-01 0:37 ` Kim Phillips
2013-02-01 10:46 ` Russell King - ARM Linux
2013-02-01 10:46 ` Russell King - ARM Linux
2013-02-01 1:17 ` [RFC] " Russell King - ARM Linux
2013-02-01 1:17 ` Russell King - ARM Linux
2013-02-01 7:33 ` Woodhouse, David
2013-02-01 7:33 ` Woodhouse, David
2013-02-06 3:04 ` Kim Phillips
2013-02-06 3:04 ` Kim Phillips
2013-02-06 9:02 ` Woodhouse, David
2013-02-06 9:02 ` Woodhouse, David
2013-02-07 1:19 ` Kim Phillips
2013-02-07 1:19 ` Kim Phillips
2013-02-07 10:19 ` Will Newton
2013-02-07 10:19 ` Will Newton
2013-02-07 10:43 ` Catalin Marinas
2013-02-07 10:43 ` Catalin Marinas
2013-02-07 18:13 ` Russell King - ARM Linux
2013-02-07 18:13 ` Russell King - ARM Linux
2013-02-08 17:25 ` Woodhouse, David
2013-02-08 17:25 ` Woodhouse, David
2013-02-08 20:04 ` Nicolas Pitre
2013-02-08 20:04 ` Nicolas Pitre
2013-02-08 22:40 ` Woodhouse, David
2013-02-08 22:40 ` Woodhouse, David
2013-02-08 22:47 ` Nicolas Pitre
2013-02-08 22:47 ` Nicolas Pitre
2013-02-09 1:12 ` Kim Phillips
2013-02-09 1:12 ` Kim Phillips
2013-02-09 3:16 ` Nicolas Pitre
2013-02-09 3:16 ` Nicolas Pitre
2013-02-20 2:31 ` Kim Phillips
2013-02-20 2:31 ` Kim Phillips
2013-02-20 2:38 ` Stephen Boyd
2013-02-20 2:38 ` Stephen Boyd
2013-02-20 3:17 ` Nicolas Pitre
2013-02-20 3:17 ` Nicolas Pitre
2013-02-20 10:38 ` Woodhouse, David
2013-02-20 10:38 ` Woodhouse, David
2013-02-20 13:36 ` Nicolas Pitre
2013-02-20 13:36 ` Nicolas Pitre
2013-02-20 13:44 ` Woodhouse, David
2013-02-20 13:44 ` Woodhouse, David
2013-02-20 14:06 ` Nicolas Pitre
2013-02-20 14:06 ` Nicolas Pitre
2013-02-20 14:53 ` Woodhouse, David
2013-02-20 14:53 ` Woodhouse, David
2013-02-20 15:43 ` Nicolas Pitre
2013-02-20 15:43 ` Nicolas Pitre
2013-02-21 3:49 ` Kim Phillips
2013-02-21 3:49 ` Kim Phillips
2013-02-21 4:29 ` Nicolas Pitre
2013-02-21 4:29 ` Nicolas Pitre
2013-02-21 6:52 ` Kim Phillips
2013-02-21 6:52 ` Kim Phillips
2013-02-21 16:40 ` Nicolas Pitre
2013-02-21 16:40 ` Nicolas Pitre
2013-02-22 2:33 ` Kim Phillips
2013-02-22 2:33 ` Kim Phillips
2013-02-22 3:40 ` Nicolas Pitre
2013-02-22 3:40 ` Nicolas Pitre
2013-02-23 1:40 ` [PATCH v6] " Kim Phillips
2013-02-23 1:40 ` Kim Phillips
2013-02-23 2:40 ` Nicolas Pitre
2013-02-23 2:40 ` Nicolas Pitre
2013-02-23 23:20 ` Woodhouse, David
2013-02-23 23:20 ` Woodhouse, David
2013-05-23 16:46 ` [PATCH v7] " Kim Phillips
2013-05-23 16:46 ` Kim Phillips
2013-05-23 20:09 ` Nicolas Pitre
2013-05-23 20:09 ` Nicolas Pitre
2013-05-23 23:13 ` Russell King - ARM Linux
2013-05-23 23:13 ` Russell King - ARM Linux
2013-06-06 22:12 ` Russell King - ARM Linux
2013-06-06 22:12 ` Russell King - ARM Linux
2013-06-06 22:23 ` Borislav Petkov
2013-06-06 22:23 ` Borislav Petkov
2013-06-07 0:03 ` Stephen Rothwell
2013-06-07 0:03 ` Stephen Rothwell
2013-05-26 5:38 ` Dirk Behme
2013-05-26 9:30 ` Woodhouse, David
2013-10-27 2:41 ` Nicolas Pitre
2013-10-27 2:41 ` Nicolas Pitre
2013-11-05 21:45 ` Kim Phillips
2013-11-05 21:45 ` Kim Phillips
2013-02-21 16:37 ` [RFC] " Woodhouse, David
2013-02-21 16:37 ` Woodhouse, David
2013-02-21 17:27 ` Nicolas Pitre
2013-02-21 17:27 ` Nicolas Pitre
2013-03-13 13:35 ` Woodhouse, David
2013-03-13 13:35 ` Woodhouse, David
2013-01-29 14:13 ` Russell King - ARM Linux
2013-01-29 14:13 ` Russell King - ARM Linux
2013-01-29 14:43 ` Woodhouse, David
2013-01-29 14:43 ` Woodhouse, David
2013-01-29 14:53 ` Rob Herring
2013-01-29 14:53 ` Rob Herring
2013-01-29 15:10 ` Woodhouse, David
2013-01-29 15:10 ` Woodhouse, David
2013-01-31 11:44 Woodhouse, David
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