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Re: [PATCH] Value profile based optimizations, part 1

On Mon, Jun 09, 2003 at 04:51:36PM +0100, Nathan Sidwell wrote:
> Jan Hubicka wrote:
> >There is another related problem - number of optimizations are
> >inaplicable for -O2 by default, but they can be when profile feedback is
> >available.  For instance loop unrolling with profile feedback brings
> >quite small code size growth relative to the speedups. (simply with
> >profile feedback compiler has enought information to decide sanely,
> >while without it it can not).
> >I am not sure wow we want to deal with this, but I would like some of
> >the options otherwise applicable only for -O3 to be enabled by default
> >at -O2 with profile feedback.  Does this sound sane?
> certainly does. Perhaps at -O2 we should look for a .da file, and if found

Yeah, I think this is an excellent idea.  You probably want these if
you're using profile feedback.

> turn on those optimizations, if not found don't. This might be acheived
> by turning them on at -O2 and then silently turn them off if the .da data
> lookup fails (i,e, make the flags tri-valued, off/on/weakly-on).

Don't we normally require an option before searching for a .da file? 
With that option and if a .da file is found, then this seems like a
good idea.

Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

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