only for exceptions.
While adding this to exception_save and exception_restore, it was hard
to find a good place to put the instructions. The code sequence was
sufficiently arbitrarily ordered that the density was low (roughly 67%).
No explicit bundling was used.
Thus, I rewrote the functions to optimize for density (close to 80% now),
and added explicit bundles and nop instructions. The immediate operand
on the nop instruction has been incremented with each instance, to make
debugging a bit easier when looking at recurring patterns. Redundant
stops have been removed as much as possible. Future optimizations can
focus more on performance. A well-placed lfetch can make all the
difference here!
Also, the FRAME_Fxx defines in frame.h were mostly bogus. FRAME_F10 to
FRAME_F15 were copied from FRAME_F9 and still had the same index. We
don't use them yet, so nothing was broken.
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