[Compiler] fix some cycle_fix_limited usage (#57545)
Recompute some O(n) things a bit less on every statement. Fix an assert
that ensured LimitedAccuracy does not accidentally get preserved when it
should have been deleted: the (local) cache should not contain things
that are marked as dead (RIP), as that was leading to much code not
getting cached when it logically should have. Simplify the computation
of frame_parent when the cycle_parent isn't needed.
