[weberc2]

Is it creating vectors in the hot path? I'm not seeing it. Go does some escape analysis (the optimization you're referring to), but it's pretty conservative.

[Lerc]

All of the vector operations return new vectors instead of mutating.

    func v3_add (a, b v3) v3 {
     return v3{x: a.x + b.x, y: a.y + b.y, z: a.z + b.z}
    }

A sensible approach for maintainable code but without knowing if a and b are used elsewhere the compiler can't reuse the space they occupy. If C can't figure it out, it can just stick a new one on the stack which doesn't cost too much.

This is, of course, Rust's bread and butter which is probably why it takes the top spot.

[weberc2]

Those are copied on the stack, not heap allocated, so the GC wouldn't come into play.