[llvm] LoopVectorize: Set branch_weight for conditional branches (PR #72450)

[Matthias Braun via llvm-commits]

MatzeB wrote:

There is no measurable performance change from that on our end. I am merely hunting down conditional branches without profile annotation which I think we can agree are never desirable in a function that has otherwise profile annotations.

https://github.com/llvm/llvm-project/pull/72450