Re: Project RABLET

[Rask Ingemann Lambertsen <rask at sygehus dot dk>]

On Fri, Jun 23, 2006 at 03:23:04PM -0400, Andrew MacLeod wrote:
> A new register allocator written from scratch is a very long term
> project (measured in years), and there is no guarantee after all that
> work that we'd end up with something which is remarkably better. One
> would hope that it is a lot more maintainable, but the generated code is
> a crapshot. It will surely look better but will it really run faster?
> The current plate of spaghetti we call the register allocator has had a
> lot of fine tuning go into it over the years, and it generally generates
> pretty darn good code IF it doesn't have to spill much, which is much of
> the time.

One area where the current register allocator is really lousy is when faced
with pseudos spanning multiple registers. A recent example:
<URL:http://gcc.gnu.org/ml/gcc-help/2006-04/msg00064.html>. And 16-bit
targets suffer from this much of the time. I can only imagine that the AVR
camp must be tearing their hair out in frustration. The register allocater
really needs to be able to allocate subregs independently.

-- 
Rask Ingemann Lambertsen