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Re: Unroller with branch and count patch


> This patch is intended for GCC mainline. It enables the GCC 3.4 new 
> unroller to work with loops ending with an branch and count instruction 
> (this is a frequent case on Power due to the doloop optimization).
> It corrects the regression seen for the GCC 3.4 new unroller on Power 
> platforms for the option -funroll-loops (we intend to submit this patch 
> also to GCC 3.4).

I don't think it is a good idea to include this in mainline (for one
reason, it does not apply any more -- simple loop analysis was rewritten
recently and moved to loop-iv.c); tomorrow I am going to send the
rewrite of the doloop optimization pass, thus making this completely

Considering 3.4, could you please send some performance numbers? I would
be especially interested in seeing differences between

-funroll-loops -fbranch-count-reg without the patch
-funroll-loops -fno-branch-count-reg without the patch


-funroll-loops -fbranch-count-reg with the patch.

on some benchmark.


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