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Re: compiling very large functions.
> Brooks Moses wrote on 11/06/06 17:41:
>
> >Is there a need for any fine-grained control on this knob, though, or
> >would it be sufficient to add an -O4 option that's equivalent to -O3 but
> >with no optimization throttling?
> >
> We need to distinguish two orthogonal issues here: effort and enabled
> transformations. Currently, -O3 means enabling transformations that (a)
> may not result in an optimization improvement, and (b) may change the
> semantics of the program. -O3 will also enable "maximum effort" out of
-O3 enables inlining, unswitching and GCSE after reload. How those
change semantics of the program?
For me -O3 always meant that we enable the code expanding optimization
that usualy speeds up, but the code size cost might not be worth it.
Honza
> every transformation.
>
> In terms of effort, we currently have individual knobs in the form of -f
> and/or --params settings. It should not be hard to introduce a global
> -Oeffort=xxx parameter. But, it will take some tweaking to coordinate
> what -f/--params/-m switches should that enable.