Pre-RFC: optimise(size) and optimise(no) attributes

[comex]

@nagisa

Sadly, no. There are a few angles to this answer, one of which is that property of optimisation is a whole-crate one – optimisation does not only optimise within a function, but also across functions as well (inlining is such an example of cross-function optimisation). For e.g. modules such attribute would make a lot of sense,

I don't think it makes sense to associate codegen options with a construct that in Rust is supposed to be just for scoping.

@nagisa

but LLVM doesn’t currently expose an attribute to achieve that, so workarounds like translating the module into a separate object/codegen-unit would be necessary.

Mm, this is too bad, and indeed it seems that Clang doesn't support the attribute-optimize GCC extension you mentioned under prior art. Nevertheless, that workaround doesn't seem infeasible at all, though it would be more complicated than just exposing optsize and optnone.