sparc64 vs. gcc 4.8

Hello,

I didn't really notice the switch since all my build scripts had
HAVE_GCC=45 left over from the previous round of updates. Since
removing them I ran into a bunch of problems. Userland seems to be
fine, kernels not so much:
- recent SMP kernels on my U60, built with gcc 4.5 are rock stable. The
  same built with gcc 4.8 ( same hardware, same source tree ) will
  spontaneously reboot ( with nothing in the message buffer so no
  panic message ), virtual console switching won't work right ( console
  just freezes, no updates occur ) and X won't start. I didn't get
  around to investigate in detail but as I said, each and any of these
  issues go away by switching compilers and rebuilding the kernel.
- similar problems seem to exist on the Blade 2500, although it's more
  complicated by other issues that crept in lately. I've seen the
  machine do both deadlocks and spontaneous reboots, still trying to
  figure out which is triggered by what. 

No idea if any of this happens on UP machines, the only one I've got is
off limits for this kind of experiments.

So, is anyone else seeing similar problems?

have fun
Michael