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

Chen Gang
2016-08-29T21:47:54Z

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@emindsoft.com.cn wrote:
>>> From: Chen Gang <chengang@emindsoft.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@gmail.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)

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