This might be slightly faster since we're doing one read rather than two before we decide to skip. The more important reason, however, is because no_spill prevents us from re-spilling spill registers. In the new world in which we don't re-calculate liveness every spill, we may not have valid liveness for spill registers so we shouldn't even look their live ranges up.
- Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110825
- Fixes: e99081e7 "intel/fs/ra: Spill without destroying the..."