[llvm] [LLVM] Add new attribute has_fake_use for llvm.fake.use-specific logic (PR #109997)

[Stephen Tozer via llvm-commits]

SLTozer wrote:

Closed in favour of https://github.com/llvm/llvm-project/pull/110097, which takes a simpler approach.

https://github.com/llvm/llvm-project/pull/109997