[llvm] [llvm-mca] Add optional identifier field to mca::Instruction (PR #97867)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

It sounds like the value here is for llvm-mcad to explore whether receiving metadata is valuable. IIRC, the original providing metadata did not turn out to be useful. 

I have two ideas here: 
1. We hold off on taking this change until there is proof that llvm-mcad benefits from receiving metadata. Otherwise, there are no known instances where this change is valuable. 
2. We take this change since it is a small addition to the size of the object and non-invasive otherwise? Perhaps we can mark it as experimental, in the case that llvm-mcad receiving metadata proves to not be useful (I.e. no known users of the field exist in the wild). 

I lean towards (1), but I wouldn’t mind (2) if someone felt strongly towards it. What do others think?

https://github.com/llvm/llvm-project/pull/97867