[clang] [llvm] [Sanitizers] Support sanitizer instrumentation regions in KMSAN, KASAN, KCOV and KCSAN (PR #231374)

[Marco Elver via cfe-commits]

https://github.com/melver commented:

I think this is complex enough that it needs an RFC, esp. since new builtins on both Clang and LLVM IR side are involved.

The feature is clear enough to me and I remember why this was asked, but it adds a ton of complexity. For KASAN and KCSAN, lack of instrumentation is just a blind spot, so that could theoretically be ignored -- but in the interest of completeness and consistency, having support for most sanitizers makes sense as proposed.

But I understand why KMSAN needs it. I just thought there might be a simpler solution, but I think those were all rejected?

https://github.com/llvm/llvm-project/pull/231374