[llvm] [DebugInfo] Don't apply is_stmt on MBB branches that preserve lines (PR #108251)

[Paul T Robinson via llvm-commits]

pogo59 wrote:

Stephen wrote this patch at my request; we have code that will now (after the previous patch to set is_stmt on each bb) stop multiple times on the same line, because of a macro that expands to multiple bbs.

Because I asked for it, but it looks more complex than I was hoping, I think other people should review it. Also, can we get some compile-time performance data? It must degrade some.

https://github.com/llvm/llvm-project/pull/108251