[llvm] [SandboxVec] Simple Instruction Interval class (PR #108882)

[via llvm-commits]

vporpo wrote:

> could use some doxygen

Do you mean like adding more comments? 

> to me it reads like an analysis and could be placed in https://github.com/llvm/llvm-project/tree/main/llvm/include/llvm/SandboxIR

I think of it more like a helper class for the vectorizer, rather than an analysis. It's not specific to the vectorizer, so it would make sense to move it into `SandboxIR`, but I think that there won't be any other users for it outside the vectorizer. If that changes we can move it then.

Regarding the Dependency Graph, that class is specific to the vectorizer. It's not going to be a generic Dependency Graph that others could use.

https://github.com/llvm/llvm-project/pull/108882