[llvm] [mlir] [polly] [IR] Only allow lifetime.start/end on allocas (PR #149310)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

LGTM

There's possibly some underlying need for "lifetimes" with different rules.  Like, if you want to implement malloc.  But allocas are special because the backend handles allocation/deallocation, so I think it makes sense to have dedicated intrinsics specifically for alloca.

https://github.com/llvm/llvm-project/pull/149310