Implement three-level optimize_for_size predicates

[Jan Hubicka]

> On 10/26/20 3:22 PM, Jan Hubicka wrote:
> > Hi,
> > this patch implements thre two-state optimize_for_size predicates, so with -Os
> > and with profile feedback for never executed code it returns OPTIMIZE_SIZE_MAX
> > while in cases we decide to optimize for size based on branch prediction logic
> > it return OPTIMIZE_SIZE_BALLANCED.
> 
> Hello.
> 
> Do we want to somehow correspondent to -fprofile-partial-training? Or is the
> -fprofile-partial-training option basically dead with your new levels?

partial-training will set counts to guessed 0 instead of absolute 0, so
we will use OPTIMIZE_SIZE_BALLANCED instead of MAX for things that was
not executed.
We will still use MAX for portions with optimize_size and code detected
by safe heuristics, like code just before abort.

Honza
> 
> Thanks,
> Martin