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Re: [patch] Remove strange case cost code
> > Note that it would make a lot of sense to teach this heuristics predict.c
> > and properly identify chars.
>
> Indeed this would be the proper place to implement this logic.
TO a degree - switch expansion needs more info than it can obtain from edge
profile. Having
switch
case 1,3,5,7,8,9: aaa
case 2,4,6,8,10,12: bbb
to produce well ballanced decision tree, it is not enough to know how
often the value is even and how often it is odd...
Thus there is a need for value histograms.
>
> > Also it is possble to get an historgrams from profile feedback into
> > switch expansion. I always wanted to do that once switch expansion code
> > is cleaned up and moved to gimple level...
>
> Indeed. At least the parts that expand switch stmts to (balanced) trees
> should be moved to the GIMPLE level, retaining only the table-jump-like
> expansions as switch stmts.
Yep.
Honza
>
> >>
> >>
> >> The attached patch removes the heuristic.
> >>
> >> Bootstrapped and tested on powerpc-unknown-linux-gnu. OK for trunk?
>
> Ok.
>
> Thanks,
> Richard.
>
> >> Ciao!
> >> Steven
> >
> >