I can't try it out, since it doesn't apply any more (I guess that's
what happens if you take too long to review something), but it seems
to me that it should have no effect on the behavior of the code at
all, since frame_id_eq actually ignores the PCs of the frame_ids it's
passed, so frame_id's behave just like the frame base addresses the
code used before. Is that right?
Yes, that is correct. The code in frame_id_eq() is intentionally
missing (I've tried adding it but it has zero effect on the i386 test
results -> need more tests :-().