performance comparison post

[Jan Hubicka]

> > Any comment on the following?
> > 
> > http://blog.regehr.org/archives/320
> > 
> > 1) is due to lack of non-linear induction variable support

Yep.  We might however also teach unroller to fully unroll the loop if we
improve constant_after_peeling.  This is probably good idea too, since we do
have different kinds of loop carried vars that not always simplify.

> > 5) is the same problem mentioned in pr35363
> > 
> > I have not looked at the details of others -- there are probably
> > related missed-optimization bugs already filed.
> 
> 7) is probably best handled by extending switch conversion pass to discover switches
> written as sequences of ifs and then convert two way switches into bitmask operation.
> This was requested by kernel folks for a while. 

I filled this in as enhancement PR46935.

Honza