Current implementation of LI verifier isn't ideal and fails to detect
some cases when LI is incorrect. For instance, it checks that all
recorded loops are in a correct form, but it has no way to check if
there are no more other (unrecorded in LI) loops in the function. This
patch adds a way to detect such bugs.
Examples of potential use:
- In PR28888 loop-unroll breaks LI, but we don't detect it (with this patch we will).
- IRCE breaks LI in IRCE/with-parent-loops.ll test. I'm xfail-ing this test for now (I'll file a separate PR for it).