[llvm] [DebugCounter] Add support for non-continous ranges. (PR #89470)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

Thank you for making those changes! All the strictly DebugCounter-related changes look good to me, though I just realized that DebugCounter.h is a file header that is obsoleted by your changes so please update that.

I still think the "delta-driver" name is too generic. Yes, it could hypothetically be used for more than just debug counter. On the other hand, `bugpoint` and `llvm-reduce` are also delta debugging tools but don't make as far-reaching a claim to being "delta drivers". So I still think searching for a better name is worth it. I proposed `minimize-debug-counter` previously -- how about `reduce-counter-chunks` or `reduce-indices` or something of that nature? It seems to me that there is inherently something being counted here since the tool is really reducing a set of numbers. What do you think?

Apart from that, there are still two changes that just don't live up to the standards we should expect as far as I can see, and frankly it'd be best to put them in a separate PR because they are logically separate:

* The PassManager changes; there isn't even a test for the new counter, let alone documentation
* The bisector tool is wholly undocumented. Thanks for explaining it a bit more in the PR, but I think it needs some more lasting documentation, if only in a header comment.

The bisector also suffers from problematic naming IMHO. What exactly does it bisect? You may as well have called it "delta-driver", to be honest. After all, its meant for delta debugging and drives the compiler :)

https://github.com/llvm/llvm-project/pull/89470