Re: Make SPEC2000 and the new allocator

[Daniel Berlin <dberlin at dberlin dot org>]

On Thu, 18 Jul 2002, Jan Hubicka wrote:

> > 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?

No, we insert spill code, not reload.

> 
> Honza
> > --Dan
> 
>