[clang] [llvm] [AllocToken, Clang] Implement __builtin_infer_alloc_token() and llvm.alloc.token.id (PR #156842)

[Marco Elver via llvm-commits]

melver wrote:

I'll take another stab at this one now, and see if I can make it constexpr, too. From what I understood that was the biggest issue. One problem is that I'm trying to figure out a sane way to share the token ID generation logic, which depends on the way AllocTokenPass was instantiated as well, without actually instantiating that pass.

https://github.com/llvm/llvm-project/pull/156842