Re: RFC: Code size improvement for global alloc

["Vladimir N. Makarov" <vmakarov at redhat dot com>]

David Edelsohn wrote:

> > > > > > Vladimir Makarov writes:
> > > > > >            
>
>  
>
> > Also I am working on more broad allocator improvements. If it will be ok,
> > the patch will be obsolete. But I can tell this only in a few months.
> >    
>
> 	Would you like to share with us what experiment you are trying?
>
>  
My general direction is a better coordination of the old allocator and 
reload to get a decision in choosing 
assigning/coalescing/splitting/rematerialization.   I am trying several 
approaches.  The last thing what I tried is PBQP (partitioned boolean 
quadratic optimization problem). This is a specific form of the 
quadratic assignment problem (QAP).  It is good model to describe 
coalescing and register assignment.  I used a heuristic (and its some 
modifications) from article "/Register allocation for irregular 
architectures"./  Unfortunately I had practically the same result as gcc 
original register allocator on SPECInt2000.

It is hard to describe other details because I am getting ideas 
practically every week or two.  I've got feeling (probably it is obvious 
for somebody) that reload (in current state) is a main obstacle for good 
register allocation.

I don't know a final result. If I get something worth, I'll create a 
branch for this.  It will need debuging and polishing for other 
platforms because my major target platform is x86.  Currently I have 
nothing that is worth and there is a big probability that the project 
will fail.

Vlad