Re: Make SPEC2000 and the new allocator

[Michael Matz <matz at suse dot de>]

Hi,

On Thu, 18 Jul 2002, Daniel Berlin wrote:

> > [... not using mmx regs for stack pseudo, idea to use xmm regs ...]
>
> No, we insert spill code, not reload.

Yes, but it's all not that big an issue.  The registers which are now only
based on GENERAL_REGS are the ones I call stack pseudos.  This doesn't
apply to normal spill temporaries.

The stack pseudos really stand for stackslots, i.e. they were produced in
a former pass of allocation instead of a stack slot to hold the value of a
spilled web.  The reason I do not use stack slots is, that I can better
track the lifetime of this thing, when it's a pseudo.  So it later has the
chance (due to other webs also spilled) to become colorable again, so in
the end maybe no stackslot is needed.  But that's a pure optimization
already.  If such stack pseudo doesn't get a color, it will be literally
replaced by a stack slot.  This also means that these stack pseudos are
not spilled again, if they don't get a color.  Basically they are handled
like colorable stackslots, which can be replaced back by registers.

Using a reg class and narrowing it down based on the mode is anyway just
an intermediate solution until we have really constraint based register
set choosing for webs.


Ciao,
Michael.