[llvm] [PGO]add bitcode-use-sample-profile (PR #66178)

[William Junda Huang via llvm-commits]

huangjd wrote:

I think this is an issue with LLVM pipeline. Functions are marked as "use-sample-profile" at front end when compiling from C++ source code (At clang::ParseAST -> ... -> CodeGenModule::EmitGlobal), but when compiling LLVM bitcode, it will not go through the parser frontend, instead go directly to optimization passes, so no function attributes will be added to the existing ones from the bitcode. It is a design decision whether it should be allowed to add/override this (or any) attribute in the bitcode 

https://github.com/llvm/llvm-project/pull/66178