linux-kernel - Re: [PATCH] arch: all: include: asm: bitops: Use bool instead of int for all bit test functions

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Date:   Tue, 30 Aug 2016 05:49:05 +0800
From:   Chen Gang <chengang@...ndsoft.com.cn>
To:     Vineet Gupta <vgupta@...opsys.com>, Arnd Bergmann <arnd@...db.de>
CC:     akpm@...ux-foundation.org, minchan@...nel.org, vbabka@...e.cz,
        gi-oh.kim@...fitbricks.com, iamjoonsoo.kim@....com,
        hillf.zj@...baba-inc.com, mgorman@...hsingularity.net,
        mhocko@...e.com, rientjes@...gle.com, linux-kernel@...r.kernel.org,
        rth@...ddle.net, ink@...assic.park.msu.ru, mattst88@...il.com,
        linux@...linux.org.uk, catalin.marinas@....com,
        will.deacon@....com, hskinnemoen@...il.com, egtvedt@...fundet.no,
        realmz6@...il.com, ysato@...rs.sourceforge.jp, rkuo@...eaurora.org,
        tony.luck@...el.com, fenghua.yu@...el.com, geert@...ux-m68k.org,
        james.hogan@...tec.com, ralf@...ux-mips.org, dhowells@...hat.com,
        deller@....de, benh@...nel.crashing.org, paulus@...ba.org,
        mpe@...erman.id.au, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, dalias@...c.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] arch: all: include: asm: bitops: Use bool instead of
 int for all bit test functions


On 8/30/16 00:48, Vineet Gupta wrote:
> On 08/29/2016 06:03 AM, Arnd Bergmann wrote:
>> On Sunday 28 August 2016, chengang@...ndsoft.com.cn wrote:
>>> From: Chen Gang <chengang@...ndsoft.com.cn>
>>>
>>> Also use the same changing to asm-generic, and also use bool variable
>>> instead of int variable for mips, mn10300, parisc and tile related
>>> functions, and also avoid checkpatch.pl to report ERROR.
>>>
>>> Originally, except powerpc and xtensa, all another architectures intend
>>> to return 0 or 1. After this patch, also let powerpc and xtensa return 0
>>> or 1.
>>>
>>> The patch passes cross building for mips and parisc with default config.
>>> All related contents are found by "grep test_bit, grep test_and" under
>>> arch sub-directory.
>>>
>>> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
>>
>> This seems like a good idea overall, and I'm fine with the asm-generic
>> contents. If there is consensus on changing this, we probably also want
>> to do some other steps:
>>
>> - Change the Documentation/atomic_ops.txt file accordingly
>> - split up the series per architecture (I don't think there are any
>>   interdependencies)
>> - For the architectures on which the definition changes (at least
>>   x86 and ARM), do some more sanity checks and see if there are
>>   noticeable changes in object code, and if so whether it looks
>>   better or worse (I'm guessing it will be better if anything)
> 
> For ARC atleast, it will be slightly worse. As bool is promoted to int in various
> expressions, gcc generates an additional EXTB (extend byte) instruction.
> 

Could you provide the related proof?

Or shall I try to analyze about it and get proof?

Thanks.
-- 
Chen Gang (陈刚)

Managing Natural Environments is the Duty of Human Beings.