In article <3be6c99a@news.povray.org> , Warp <war### [at] tagpovrayorg>  wrote:

>  Nowadays processors have extremely advanced
> loop optimizations in themselves and usually we don't need to "guide" the
> processor in doing it.

Which will still fail when the exit condition of the loop cannot be
determined early enough.  Unless you assume every processor design today
supports speculative execution of both possible branch directions.  And even
more important, speculative execution takes a lot of resources, which not
only adds to the complexity of the processor, but most notably to the power
consumption.  That is why most embedded processors have only minimal (if any
at all) support for branch prediction and other optimizations most of which
a good compiler could have made in the first place (i.e. out of order
execution) thus a very low power consumption.  For those a partial unrolling
of a loop with be a major performance gain at a relatively low cost of
memory.


    Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

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