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List:       wine-devel
Subject:    Re: Const Function Parameters?
From:       Joseph Garvin <k04jg02 () kzoo ! edu>
Date:       2005-07-28 22:06:03
Message-ID: 42E956CB.6000206 () kzoo ! edu
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Has anyone checked if the performance improvement stays if only the
pointers are set to const?

I'd also suggest running the test multiple times and averaging.

Felix Nawothnig wrote:

> Andreas Mohr wrote:
>
>> While I'm not too convinced in this case (1.5% improvement sounds like
>> within statistic noise), it should be a good idea to mark things in Wine
>> const whenever possible (objdump -x helps here), since it improves 
>> reliability
>
>
> Huh? He did stuff like...
>
> -void foo(int i)
> +void foo(const int i)
>
> This will most likely not improve reliability. He also changed some 
> pointers to const which is wanted and will ofcourse improve reliability.
>
> Assuming that gcc has a pretty good optimizer the only reason I can 
> think of (besides a GCC bug :-) why performance increased is that gcc 
> doesn't have to perform aliasing-analysis and can be sure that the dst 
> pointer will never point into local parameters (constifying local 
> variables could speed up things slightly more).
>
> I'm not sure about the "restrict" semantics but maybe it could be used 
> instead of constifying "int i" to archieve the same effects?
>
> Felix
>



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