Re: [PATCH 01/10] Fix IRA ICE.

[Andrew Stubbs <ams@codesourcery.com>]

On 21/11/2018 00:47, Jeff Law wrote:
> This seems like a really gross hack and sets an expectation that
> generating registers in the target after IRA has started is OK.  It is
> not OK.  THe fact that this works is, IMHO, likely an accident.

What's the proper test for this? Neither lra_in_progress nor 
reload_in_progress is set here, and can_create_pseudos returns true.

The patterns have the ability to not generate registers, but they don't 
know not to.

Richard Sandiford has stated that it should be OK, but perhaps the other 
architectures also work by accident?

In fact, since we're using LRA (not reload), my understanding is that I 
ought to be able to create new pseudos right up until reload_completed. 
(Although, my experience is that it's easy to get into an infinite loop 
doing that.)

> I think this comes back to the fundamental representational issue with
> the EXEC handling that still needs to be addressed.

Undoubtedly, this makes it worse, but even without that I'd still want 
to expand vector memory moves long before split1, so at least some cases 
have to generate additional registers. (Perhaps IRA doesn't create 
memory moves though? I'm not sure.)

I'm going to investigate how easy it is to fix the EXEC representation 
issues. I've been resisting because I had a deadline to make, and it's 
bound to be an invasive and destabilizing alteration (albeit largely 
mechanical), but if it's going to be a barrier to commit then probably 
it's become time. :-(

Andrew