RFC: allowing fwprop to propagate subregs

[Paolo Bonzini]

On 09/14/2011 05:44 PM, Richard Sandiford wrote:
>> >  A SUBREG may not be REG nor CONSTANT. Don't you need
>> >  to check REG_P/CONSTANT_P on SUBREG?
>
> Yeah, good point.  There should be a "&&  REG_P (SUBREG_REG (new_rtx))"
> in there.  Probably also worth checking for non-paradoxical subregs.

I was going to suggest the former.

Paradoxical subregs are already handled elsewhere in fwprop, but it also 
shouldn't hurt to include them.

Paolo