[llvm] [DebugInfo] Don't set prologue_end behind line-zero call insts (PR #156850)

[David Blaikie via llvm-commits]

dwblaikie wrote:

Thanks for all the details - given the rarity, if you just wan to move forward with this as-is, I'm OK with it.

But for argument's sake: What about if we forced the location after the prologue, if it's line zero, to instead have the function's scope start location.

This would mean if you broke inside the function call - you'd see the caller frame as being at the start of the calling function, not line zero, which might be misleading - since that line doesn't necessarily have a function call on it. But maybe isn't /too/ wrong? (it's not bonus coverage, at least - the start of the caller is certainly reached/that is where you're at) - and in many cases, the start of the function scope isn't some other line of code - it's the opening brace, so it'd be maybe a bit clear that we're not trying to describe a specific bit of code... 

It's not super principled, by any means... 

https://github.com/llvm/llvm-project/pull/156850