[llvm] [ConstantHoisting] Add a TTI hook to prevent hoisting. (PR #69004)

[David Sherwood via llvm-commits]

https://github.com/david-arm approved this pull request.

LGTM! After looking at the code and trying to understand the comments, I think overall this is the best approach. It looks like changing the meaning of getIntImmInstCost() will likely break other existing code.

https://github.com/llvm/llvm-project/pull/69004