Re: [patches] Re: limited register renaming at -O2

[Jan Hubicka <jh at suse dot cz>]

> 
> > This patch changes register renamer to not rename user variables unless
> > new flag messy-debugging is set.  Then I can enable it at -O2 (and get
> > most of benefit done).
> 
> I'm not too happy about this approach.  I'd prefer if the debugging output
> could be changed to deal with the effects of renaming.
> 
Even I would love to see that (and in fact I want to implement it in future),
but to my understanding, on some formats it is impossible (slabs) and we have
other places in compiler where we supress some optimizaions because of
debugging.

I am not sure what the politic is, if the target use slabs.  Would we just keep
the info unusable, or disable register renaming when slabs are used.
How we choose on thargets that use multiple outputs, like i386?

Thats why it looked to me like introducing -fmessy-debugging can be usefull
thing to do.

Honza
> 
> Bernd