[jmorse2]

> I'm referring to all the cases where the compiler obviously should know where the value is, yet the debugger somehow doesn't.

Soooommmee of this can be explained by the design decisions in the compiler not lending themselves to working well with debug-info, as explained here [0] (shamless plug), from about 3 minutes in there's an example of a scenario where a variable location has to be discarded out of conservative precaution (4:40 to 7:00), rather than because it's definitely been optimised out.

[0] https://www.youtube.com/watch?v=yxuwfNnp064&t=45s