ia64 projects

[Bernd Schmidt]

On Wed, 10 Jan 2001, Jim Wilson wrote:

> In article < OFA91E2757.0853FAB8-ON882569CF.0082A6E5@LocalDomain > you write:
> >Is there an existing wish list of projects for IA-64 code generation
> >and/or optimization?
>
> We don't have a good Itanium hardware description.  There is an improved
> pipeline description scheme that was written by Vladimir Makarov.  However,
> it hasn't been submitted to the FSF yet, and it is unclear when it will be,
> so for now we aren't using it.  When we did try to use it, we didn't get
> any noticable speedup.  It was unclear whether this was due to limitations
> with the scheduler, or whether there was something wrong with the Itanium
> pipeline description.

I think Vlad's Itanium description is actually a bit less accurate than what
we now do via MD_SCHED_REORDER.  I believe it also wasn't as good at placing
stop bits.

> The scheduler
> was creating lots of false dependencies for a while, but that may have been
> fixed already, I'm not sure.

That's mostly fixed.

> We probably need an agressive cross
> block scheduler to get much benefit from any of these areas.  I doubt we want
> to go as far as trace scheduling, but there is probably something intermediate
> that would be useful.

The code I've added to schedule across extended basic blocks seems moderately
effective (maybe 8% on SPEC with the other improvements to reduce false
dependencies).


Bernd