[clang] [llvm] [clang][Inliner] Add opt-in inliner hints for lambdas and implementation-file functions (PR #228074)

[Kuba Mracek via llvm-commits]

kubamracek wrote:

> LLVM is also supposed to be generic infrastructure for multiple frontends. This means metadata should also be general purpose and not specific to clang (or at least not named clang-* even if clang is the only emitter in practice).

I agree, that makes sense. The general phrasing of the same concept is "header files" vs "implementation files". This distinction exists in multiple frontends/languages (but not all), and where it exists, the same idea of boosting inlineability/optimizatibility of implementation-file content should apply the same way. Languages without header files  don't suffer from this problem in the first place (no over-used linkonce_odr linkage).

https://github.com/llvm/llvm-project/pull/228074