Re: is REG_WAS_0 usable in final pass

[Denis Chertykov <denisc at overta dot ru>]

Bernd Schmidt <bernds@redhat.com> writes:

> On Sat, 2 Jun 2001, Denis Chertykov wrote:
> 
> >
> > Is REG_WAS_0 usable in final pass?
> > (While backend output asm patterns)
> > `bbro' pass can change REG_WAS_0 note, but bbro don't correct it.
> >
> > Denis.
> > PS: Only 3 ports uses REG_WAS_0: vax, tahoe and AVR.
> > PS: vax and tahoe are pretty dead and I'm worry about AVR port.
> 
> I thought the i386 used it as well.  If that's no longer the case, we should
> remove support for it (unless you have a really good argument why the AVR
> needs it).  It costs too much to maintain these notes for no significant gain.

REG_WAS_0 was used by i386 port few times ago.
But now i386 isn't use REG_WAS_0.

AVR port use REG_WAS_0 for effective constant loading.
If I need to load 8 bit constant to register with mode wider than
QImode, then I use REG_WAS_0 and if it is I load only 8 bit (emit only
one command) instead of 16 or 31.

You can run `grep reg_was_0 gcc/config/avr/*' to see how many it's
used.

Please tell me if you want to drop REG_WAS_0 support.