Re: Make SPEC2000 and the new allocator

[Jan Hubicka <jh at suse dot cz>]

> On Thu, 18 Jul 2002, Jan Hubicka wrote:
> 
> > > 
> > > On Thursday, July 18, 2002, at 12:28  PM, Michael Matz wrote:
> > > 
> > > >Hi,
> > > >
> > > >this fixes a misunderstanding on my side, where the allocator on
> > > >x86 sometimes assignes registers from MMX_REGS to the stack pseudos.
> > > Err, so?
> > > 
> > > Intel's compiler does the same thing.
> > 
> > You can't do that on pre P4 machines as you need femms.
> 
> Ahh.
> At least, however, you should be able to spill to the xmm registers 
> without femms, no?
Yes, but the integer->xmm move is expensive.  You should at least
consult register move cost whether it is cheaper than memory spill.  For
Athlon reg->xmm move is more expensive than int->mem->xmm move and even
for P3/4 I believe int->xmm->int is more expensive than int->mem->int

If I understand it properly the spill registers are supposed to be
spilled by reload, so why to worry at first place?

Honza
> --Dan