Reload bug

[Jan Hubicka]

> > > What you have done is to teach the reload pass to silently transform any
> > > non-accessible part of a multi-word register into the low part.
> >
> > In the case the subreg is undable (ie it is in the SSE), or can this
> > happen in the integer register too?
> 
> Only when the logic should have triggered, i.e with MMX and SSE regs but not 
> with general regs since it doesn't trigger for them.
> 
> > Or we can backport the CANNOT_CHANGE_MODE_PATCH.
> 
> Big patch.
> 
> > I would be happy about any alternative for 3.2
> 
> Well, there aren't too many possibilities:
> - either we prevent such invalid subregs from being created in the first 
> place (but it appears that doing so brings about collateral damages in the 
> form of (subreg:SI xmm:DI 0) being now rejected?),

This is the big patch, so probably not good choice.

> - or we restore the machinery that was able to handle them.

As I tried to explain in the other email, I believe we never had any
working reliably.  For 3.2 it is probably OK to simply revert the patch
after all.  I can do so if maintainer approves that.
I just want to be sure that for 3.3/3.4 it is dealt correct that I am
not quite certain about at this point :((

Honza
> 
> -- 
> Eric Botcazou