Review Request: Four simple patches for kdecore

[Rolf Eike Beer]

Dawit Alemayehu wrote:
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> 
> I am personally not conveinced the need for changing from usleep to
> nanosleep in this particular instance. IOW, usleep is sufficient in this
> case to warrant a change regardless of when that system call was made
> available...
> 
> 
> /trunk/KDE/kdelibs/kdecore/util/kshareddatacache.cpp
> <http://svn.reviewboard.kde.org/r/5775/#comment8911>
> 
>     Hmm... why do unnecessary calculations in fast loops ? Surely
> "1<<21*10" can be hard coded with a #define.
> 
> 
> 
> /trunk/KDE/kdelibs/kdecore/util/kshareddatacache.cpp
> <http://svn.reviewboard.kde.org/r/5775/#comment8912>
> 
>     And of course if speed is an issue, which seemed to be the case since a
> left shift arithmetic was done above, this can be changed to a equivalent
> left shift operation:
> 
>     usecSleepTime.tv_nsec = usecSleepTime.tv_nsec << 1;

No, please don't do that. That advise is outdated some years. This doesn't get 
any benefit at all since every compiler not completely outdated will generate 
the same code from "a * 2" and "a << 1". They will also do precalculations of 
constants. So this would also make the code unreadable.

See e.g. http://dl.fefe.de/optimizer-isec.pdf for more information on compiler 
optimizations.

Eike
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