[llvm] [ExtendLifetimes] Implement llvm.fake.use to extend variable lifetimes (PR #86149)

[J. Ryan Stinnett via llvm-commits]

https://github.com/jryans commented:

Similar to @OCHyams, this looks good to me overall, though it does touch some parts I am not familiar with (like the legalizer). Sony's multi-year usage of this downstream adds confidence in the work. The feature as a while has received positive feedback in various discussions, so it would be great to move forward here.

I believe the only major missing component is `GlobalISel` support. Once that has been added, I think this would be ready to go.

https://github.com/llvm/llvm-project/pull/86149