On 12/10/2013 10:44 AM, Richard Sandiford wrote: > Sorry, I don't understand. I never said it was invalid. I said > (subreg:SF (reg:V4SF X) 1) was invalid if (reg:V4SF X) represents > a single register. On a little-endian target, the offset cannot be > anything other than 0 in that case. > > So the CANNOT_CHANGE_MODE_CLASS code above seems to be checking for > something that is always invalid, regardless of the target. That kind > of situation should be rejected by target-independent code instead.
But, we want to disable the subreg before we know whether or not (reg:V4SF X) will be allocated to a single hard register. That is something that we can't know in target-independent code before register allocation. > In other words I'm arguing against the idea of passing the offset to > CANNOT_CHANGE_MODE_CLASS (which you seemed to be supporting in the > quote above). I think Kirill's patch to remove the i386.c check was > the right way to go. Unless you can figure a way around the above, I think passing the offset to C_C_M_C is probably the way to go. I need to have a look over the patches though... > > There's no need for a separate insn though. Once you allow the subregs > (as per Kirill's patch), the normal move patterns will handle them. Absolutely. r~
