linux-kernel - Re: [GIT PULL] core/hweight changes for v2.6.35

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Message-ID: <AANLkTikaHsbdM0XSaHH1iE9p8cYE=YFM3an=+xB-JKgZ@mail.gmail.com>
Date:	Fri, 13 Aug 2010 17:59:41 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Borislav Petkov <petkovbb@...glemail.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [GIT PULL] core/hweight changes for v2.6.35

On Fri, Aug 13, 2010 at 17:56, H. Peter Anvin wrote:
> On 08/13/2010 02:42 PM, Mike Frysinger wrote:
>> On Mon, May 17, 2010 at 17:21, Ingo Molnar wrote:
>>>  arch/alpha/include/asm/bitops.h            |   18 +++++----
>>>  arch/ia64/include/asm/bitops.h             |   11 +++--
>>>  arch/sparc/include/asm/bitops_64.h         |   11 +++--
>>>  arch/x86/include/asm/bitops.h              |    4 +-
>>>  include/asm-generic/bitops/arch_hweight.h  |   25 ++++++++++++
>>>  include/asm-generic/bitops/const_hweight.h |   42 ++++++++++++++++++++
>>>  include/asm-generic/bitops/hweight.h       |    8 +---
>>
>> did this miss Blackfin because the original patch was against the
>> 2.6.34 tree ?  just wondering why it now build fails ...
>>
>> doing a simple grep shows that the new "tile" arch may also be broken
>> as it uses "hweight32" ...
>>
>> considering __sw_hweightX only exist when the generic hweight is in
>> play, wouldnt it make sense to have
>> include/asm-generic/bitops/arch_hweight.h not always define things ?
>> then most arches can simply pull in
>> include/asm-generic/bitops/hweight.h without having to worry about the
>> random inner details of hweight cruft.
>>
>
> __sw_hweightX can exist even when generic hweight isn't in use per se,
> because the arch implementation can wrapper the software implementation.
>  This is the case on x86, for example -- most x86 CPUs don't have popcnt
> yet, so on those the x86 implementation end up calling the
> __sw_hweight*() implementations.

but those targets still define CONFIG_GENERIC_HWEIGHT right ?  so at
the least, we should be wrapping the prototypes in linux/bitops.h with
that ...
-mike
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