[llvm] [LangRef] Specify that load of alloca outside lifetime is poison (PR #157852)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

I think, in practice, optimizations already worked this way.  Shrink-wrapping doesn't track alloca lifetimes, and without shrinkwrapping an alloca is always backed by memory anyway. And we don't have the infrastructure for IR optimizations to prove a load is outside the lifetime of an alloca.

I guess it doesn't hurt to explicitly state it, though.

https://github.com/llvm/llvm-project/pull/157852