On Tue, Mar 19, 2013 at 7:31 PM, Jeff Law wrote: > On 03/19/2013 11:58 AM, Ian Lance Taylor wrote: >> >> On Tue, Mar 19, 2013 at 8:33 AM, David Miller wrote: >>> >>> >>> So this patch tries to rework the semantics of hard register classes, >>> such that if a hard register is present in the set it is implied that >>> the rest of the registers in a multi-register group are present as >>> well. So we can add a register class called EVEN_REGS and only have >>> to set the even register bits. >> >> >> I haven't really looked at your patch, but I just want to say that I >> think this is the right way to go. > > Likewise. I've certainly worked on ports where this would have been helpful > in the past.
It could also help simplify existing ports. rs6000 has a few places where this could be useful (dfp). At least arm (VFP_REGNO_OK_FOR_DOUBLE), avr, and h8300, too. And ISTR s390 plays funny subreg tricks to get this right. Finally, it's been discussed on the gcc@ mailing list for out-of-tree ports a few times in recent history. So yes, great if this can be done! Ciao! Steven
