[llvm] [DebugInfo] Preserve line and column number when merging debug info. (PR #129960)

[Reid Kleckner via llvm-commits]

rnk wrote:

> As long as we have agreement that we need such a design and that this is the long term goal, I'm comfortable living with this (I won't even say short term, because everything lives longer than you expect) tech debt tradeoff.

To say more (I should edit more before replying), I think documenting what PGO needs from debug info is a necessary step on the path to creating this alignment. We have some of this in HowToUpdateDebugInfo.rst, but a lot of these requirements for interactive stepping, PGO control dependency, and sanitizer reports have largely been in our heads, and that makes it harder for the LLVM project to function as a globally distributed open source community. Which is why I think it's a good tradeoff to accept some tech debt for improved documentation.

https://github.com/llvm/llvm-project/pull/129960