[llvm] [MachineLICM] Hoist COPY instruction only when user can be hoisted (PR #81735)

[via llvm-commits]

michaelselehov wrote:

> Do you have a test demonstrating the problem you are running into? We usually prefer that code is accompanied by a test case to make sure we don't accidentally break it again in the future.

I have an IR derived from the benchmark which is pretty big. I reduced it down to the point when only one spill reload still appears but yet it's 685 lines big. I'll see if I can make anything prettier.

https://github.com/llvm/llvm-project/pull/81735