[llvm] [DLCov][NFC] Annotate intentionally-blank DebugLocs in existing code (PR #136192)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

> Will there be a patch coming to update the/some new getDroppeds to dropLocation?

There could be: for what it's worth, `dropLocation()` only differs from `DebugLoc::getDropped()` for instructions that may be lowered to calls, while for any other instruction they are identical. It may still be worthwhile keeping the API usage consistent, although technically using `dropLocation()` means wasting a little time checking whether the instruction is a call (when at the places where I've used it, we know that it is not).

> Just checking as I've forgotten a bit of context - is the difference between dropped/compilerGenerated relevant only for stat-collection purposes? i.e., if we mistakenly use one rather than the other, it's only going to slightly skew some stats?

Technically there's no difference between any of the annotation location types yet, but in time we can/will check numbers for each individually. There is also the possibility of validating certain annotations - the most obvious one being that we could detect if we attempt to emit any Temporary DebugLocs into the line table.

https://github.com/llvm/llvm-project/pull/136192