[clang] [llvm] [StackProtector] Introduce stack-protect-attributor pass to remove unnecessary protections. (PR #150390)

[via cfe-commits]

Mermen wrote:

> Why is this a separate pass that removes attributes from the _function_ if _all_ allocas are safe, rather than integrated with the actual stack protection, so that the decision can be made per alloca?

StackSafetyAnalysis is a module pass so using it in StackProtectorPass (which is a function pass) changes pipeline significantly (introducing spurious changes in tests and performance jitter).

https://github.com/llvm/llvm-project/pull/150390