[llvm] [MC/DC] Introduce `class TestVector` with a pair of `BitVector` (PR #82174)

[NAKAMURA Takumi via llvm-commits]

https://github.com/chapuni commented:

I would like to wait for both @MaskRay and @evodius96 , since they are authors of the current impl.

https://github.com/llvm/llvm-project/pull/82174