[llvm] [DebugInfo][DWARF] Set is_stmt on first non-line-0 instruction in BB (PR #105524)

[David Blaikie via llvm-commits]

dwblaikie wrote:

We're seeing a pretty significant size regression from this change in self-host builds of clang and some other internal binaries we track.

For an internal debug build (with Split DWARF, compressed debug info sections in object files but uncompressed in the linked binary) we saw a total 3.6% increase in the size of the clang binary, a 12.7% increase in the size of the .debug_line section in object files, and a 18.3% increase in the size of .debug_line in the linked executable.

Might be worth reverting this and reconsidering whether the growth is acceptable or whether there's a more targeted fix that can be made?

https://github.com/llvm/llvm-project/pull/105524