Ulrich Weigand wrote: > Georg-Johann Lay wrote: > >> Thanks, it works. > > OK, thanks for testing! > >> std Y+2,r31 ; 30 *movphi/3 [length = 7] >> std Y+1,r30 > > I'm actually not seeing those (maybe I'm using a different code > base than you were using ...) > > But I still see that the frame is created. The problem is that IRA > thinks it needs to allocate a pseudo on the stack, and creates a > stack slot for it. But then reload goes and just reloads the > pseudo into a hard register anyway, and simply doesn't need the > stack slot ... but it was already allocated and accounted for > such that get_frame_size () no longer returns 0.
The stack slot is an IRA hog because there are plenty of hard regs. >> I frequently see IRA doing a very bad job for small register classes >> like here. Maybe it's better to take it completely away from IRA >> and write the load as >> >> (set (reg:HI) >> (unspec:HI (post_inc:PHI (reg:PHI Z)))) >> >> Loading from __pgm is actually an unspec, i.e. reading two times from >> the same address will yield the same result. > > This really seems to be a problem in IRA somewhere, but I'd guess it > would be better to fix in there instead of working around it. Maybe > you should open a bug an get in touch with the IRA maintainers ... It surely is an IRA issue. However, it's extremely unlikely that anyone cares for SSA/RTL optimization flaws that just show up on AVR or are reported against AVR. And if a patch turns out to overcharge IRA like, e.g. in http://gcc.gnu.org/ml/gcc-patches/2011-07/msg02655.html the patch won't be integrated. Moreover, this one is hard to reproduce because it needs you patch, my patch and is for a "irrelevant" target. Johann > Bye, > Ulrich
