#[cold] attribute does is not propagated across crates

[matklad]

Hi!

When hacking on once_cell, I've noticed that it is significantly faster than lazy_static. Digging into this, it seems like the difference is in the usage of the #[cold] attribute.

Specifically, I've applied a patch which marks initialization function as #[cold] in lazy_static, and it indeed improved perf quite a bunch:

matklad/lazy-static.rs@7863cc0

And this is really weird, because Once, which powers lazy_static, already has the #[cold] attribute. Seems like it doesn't take an effect for whatever reason?

@rustbot modify labels to: +I-slow

[rustbot]

Error: Parsing label command in comment failed: ... labels to|error: a label delta at >|: +I-slow...

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