[llvm] [DebugInfo] Merge partially matching chains of textual inclusions (PR #125780)

[Anton Korobeynikov via llvm-commits]

asl wrote:

Just few side notes: while the testcase in https://github.com/llvm/llvm-project/issues/122846 was in C++, the original one was not. It was created from a non C++ source. The particular feature there is that inlining is done in (non-LLVM / non-clang) frontend, so we are losing all information similar to `inlinedAt`. 

Essentially, from the LLVM standpoint the output of this inlining procedure is similar to that of full textual inclusion by a C/C++ preprocessor (testcase in https://github.com/llvm/llvm-project/issues/122846 was created to emulate the original behavior via preprocessor). And it is important not to loose the location information for something inlined this way. But certainly it should be correct, and not something broekn `getMergedLocation` currently returns :)

https://github.com/llvm/llvm-project/pull/125780