------- Comment #5 from rguenther at suse dot de  2009-08-13 15:58 -------
Subject: Re:  invariant address load inside loop
 with -Os.

On Thu, 13 Aug 2009, rahul at icerasemi dot com wrote:

> ------- Comment #4 from rahul at icerasemi dot com  2009-08-13 15:46 -------
> Confirmed. Introducing loop header copy for Os, resolves the problem.
> On our port, this not only helps move the invariant load outside the loop, but
> also correctly uses an auto-increment address mode via the AutoInc patches we
> use. Other examples also confirm that the header copying enables more 
> induction
> variables to be identified and hence post-increment opportunities.
> 
> Does better loop analysis and hence potential for further optimizations
> outweigh the cost of copying the loop header? It would be ideal to relax the
> loop header copy predicate for Os and select an appropriate threshold,
> currently set at 20 insn, a lower value to start with perhaps.

Experimenting with that would be certainly useful.

Richard.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41026

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