[llvm] [IR] Introduce captures attribute (PR #116990)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> I'm not really sure what your godbolt example is supposed to show (I don't see any relation to provenance capture?)

`icmp ptr eq %p, %q` doesn't allow us to perform GVN for `load %p` and `load %q`, right? Another alive2 counterexample: https://github.com/AliveToolkit/alive2/issues/1110


https://github.com/llvm/llvm-project/pull/116990