Before this commit, nested loops aren't counted correctly:
-------------
V |
-> A --> B --> C ->
^ |
-------
A is both predecessor and successor of B but A isn't in B's loop.
Instead a block B is in loop header H's block if H is the successor
of B and H dominates B.
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38393>
6535a3b6b3