Unwinding on mac64 is broken with fp elim

[alexcrichton]

We recently turned on frame pointer elimination in our LLVM codegen. This is apparently causing many problems with unwinding on mac64 platforms. This isn't quite deterministic, but some patches trigger this regularly.

For now, I'm adding an exception for mac64 platforms.

[reem]

Triage: Is this still an issue? Do we want/need frame point elimination on OS X? If not or there is already a satisfactory fix this should be closed.

[alexcrichton]

Yes, in theory there is a bit of a codegen/perf improvement if we have fp elimination, but it's still disabled for mac

[steveklabnik]

@alexcrichton what about now? I can't find that code you linked to anymore, it would seem that src/librustc_back/target/apple_base.rs (which I think is the new version) mentions nothing about this.

[alexcrichton]

Ah it just moved over here (still disabled)

[steveklabnik]

Triage: no longer disabled https://github.com/rust-lang/rust/blob/691eba1358fc3c9c7a8033314a4112d43680c128/src/librustc_back/target/i686_apple_darwin.rs