On Sat, Feb 9, 2013 at 7:37 AM, Georg-Johann Lay <gjl@xxxxxxxxxxx> wrote: > Ian Lance Taylor schrieb: > >> As far as I know there is no constraint that describes only the even >> registers of the general register set. It would not be very difficult >> to add one to the PPC backend. I can't think of any other way to >> approach this. > > > AFAIK that does not work because the respective register class would have > holes. You cannot have a register class that contains only even registers > and omits the odd ones. Or can IRA / reload handle this now? To the best of my knowledge it always could. Register classes routinely have holes. I'm not sure what sort of problem you are thinking of. > One way would be to use HARD_REGNO_MODE_OK and restrict 64-bit modes to even > registers, but that would be an ABI change... Yeah, don't do that. > From the C level a local register variable could be use, thus it is possible > to describe but the results will be suboptimal because the respective > operand is not available for register allocation. Yes. Ian
