Is x = !x faster than x.toggle() because from my naked eyes no function is called? Or does the compiler know that the function toggle should be replace with `!=`? If the compiler does know that, how is that knowledge implemented? Is there a table of special functions that should be replaced with something else? Or some more clever way?

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tialaramex a day ago | parent | next [-]

Thanks to Matt Godbolt, we can ask Compiler Explorer!

https://rust.godbolt.org/z/dPn3Y4r59

The optimizer gives the exact same machine code for both functions, and so it just outputs a single function and gives it an alias.

The compiler has a technique called "inlining" https://en.wikipedia.org/wiki/Inline_expansion

The LLVM backend used by Rust is jokingly said to have a inlining heuristic of "yes" ie it will always try to inline everything because that's usually faster.

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xiej a day ago | parent [-]

Unfortunately it's not inlined in debug/no optimization mode so that's rough.

	▲	saghm a day ago \| parent \| next [-]
		I'll go out on a limb and hypothesize that there are going to be much larger difference between debug and release mode for any non-trivial code that the overhead of `toggle` in debug mode will quite literally never end up mattering to anyone in practice.
	▲	lanyard-textile 20 hours ago \| parent \| prev [-]
		Why should it be? That's a feature of debug.

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lern_too_spel a day ago | parent | prev [-]

It has the #[inline] attribute.

https://std-dev-guide.rust-lang.org/policy/inline.html

	▲	kibwen 15 hours ago \| parent [-]
		In this case the inline attribute probably isn't strictly necessary, because rustc heuristically inlines any functions that it deems trivial enough.