I don't entirely understand the description. Sorry!

If I'm reading it right, the issue is that the generated checks are checking for the presence of expected lines, but they are not checking for the absence of unexpected lines. Do I understand that correctly?

If I'm reading it right, the issue is that the generated checks are checking
for the presence of expected lines, but they are not checking for the
absence of unexpected lines. Do I understand that correctly?

Yes.

I knocked up a quick prototype that has stricter checking, but currently relies on this (uncommitted) patch: https://reviews.llvm.org/D28896

Obviously, if we go ahead with this, it will require another mass-regeneration of the tests.

Roman/Greg - is this still an issue?

Roman/Greg - is this still an issue?

Yep, still an issue.
You can see it by dropping some block of CHECK + CHECK-NEXT + CHECK-NEXT ... lines

Right. So far I've held off going further with this because I'm scared how big the diff will be if I regenerate multiple lines over every single mca test... :-\

I guess I might just have to bite the bullet and just do it, as the issue is just going to get worse as more tests are committed.