"Managed" is a strong word - there's regular complaining about compiler optimizations, there was a string of vulnerabilities where null checks were optimized out because they were secretly UB, and there was a discussion just last week about how compilers were reordering certain patterns in unexpected ways: https://linuxplumbersconf.org/event/7/contributions/821/

Quoting from the abstract of that talk: "... preserving source-level dependencies through to the generated CPU instructions is achieved through a delicate balance of volatile casts, magic compiler flags and sheer luck. Wouldn't it be nice if we could do better?"