Re: An unusual Performance approach using Synthetic registers

[Andy Walker <ja_walker at earthlink dot net>]

Do you have any idea about how well the new allocator handles two-tiered 
register classes?

Obviously, my specific interest is a small class of general registers coupled 
with a large class of quite restricted registers.

Andy

On Monday 06 January 2003 12:49 am, Daniel Berlin wrote:
> > My goal is that the generated code with Synthetic registers will be
> > significantly better (looking just at the instruction count).  If the
> > fields
> > have individual values, in your example, then Reload imposes an
> > overhead.  It
> > is a two step process: move the spilled data back into a register,
> > then use
> > it.  With a Synthetic, you get to just use it.
>
> If the new allocator determines the data in question is cheaper to
> recalculate than it would be to reload it from memory, it'll do so
> (though it might be a bit limited in what it *can* recalculate right
> now, this is fixable. I don't have numbers on how often it would have
> wanted to remat but couldn't due to these problems). It's known as
> "rematerialization".
> Thus, in the example of vtable pointers, it'll simply recalculate the
> value into the new register, rather than reload it from memory.
>
> > Andy