Inlining small non-recursive functions

[catamorphism]

I know that inlining heuristics are a black hole. However, it seems that we're growing lots of #[inline_always] attributes on small non-recursive functions. I have no idea what mechanism LLVM has for inlining hints (besides "always inline" annotations on a function), but telling it to always inline non-recursive functions below a certain size threshold would reduce the amount of clutter.

[Aatch]

LLVM will potentially inline any function. It uses a threshold size for it, which is modified by inlinehint and overridden with always_inline.

[thestinger]

It can't inline cross-crate though without #[inline] because we aren't usually outputting the AST.

[Aatch]

@thestinger I'd say thats a separate issue. Either @huonw's #[inline(maybe)] makes it in, or we take a guess at intent and output the ast, sans #[inline] attribute.