Migrate to core::hint::black_box()
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…tead `core::hint::black_box()` has no performance overhead, and is the preferred method of blocking optimizations in benchmarks. It was likely introduced after our benchmarks were created, which is why we didn't use it before.
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# Objective Many of our benchmarks use [`criterion::black_box()`](https://docs.rs/criterion/latest/criterion/fn.black_box.html), which is used to prevent the compiler from optimizing away computation that we're trying to time. This can be slow, though, because `criterion::black_box()` forces a point read each time it is called through [`ptr::road_volatile()`](https://doc.rust-lang.org/stable/std/ptr/fn.read_volatile.html). In Rust 1.66, the standard library introduced [`core::hint::black_box()`](https://doc.rust-lang.org/nightly/std/hint/fn.black_box.html) (and `std::hint::black_box()`). This is an intended replacement for `criterion`'s version that uses compiler intrinsics instead of volatile pointer reads, and thus has no runtime overhead. This increases benchmark accuracy, which is always nice 👍 Note that benchmarks may _appear_ to improve in performance after this change, but that's just because we are eliminating the pointer read overhead. ## Solution - Deny `criterion::black_box` in `clippy.toml`. - Fix all imports. ## Testing - `cargo clippy -p benches --benches`
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# Objective Many of our benchmarks use [`criterion::black_box()`](https://docs.rs/criterion/latest/criterion/fn.black_box.html), which is used to prevent the compiler from optimizing away computation that we're trying to time. This can be slow, though, because `criterion::black_box()` forces a point read each time it is called through [`ptr::road_volatile()`](https://doc.rust-lang.org/stable/std/ptr/fn.read_volatile.html). In Rust 1.66, the standard library introduced [`core::hint::black_box()`](https://doc.rust-lang.org/nightly/std/hint/fn.black_box.html) (and `std::hint::black_box()`). This is an intended replacement for `criterion`'s version that uses compiler intrinsics instead of volatile pointer reads, and thus has no runtime overhead. This increases benchmark accuracy, which is always nice 👍 Note that benchmarks may _appear_ to improve in performance after this change, but that's just because we are eliminating the pointer read overhead. ## Solution - Deny `criterion::black_box` in `clippy.toml`. - Fix all imports. ## Testing - `cargo clippy -p benches --benches`
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Objective
Many of our benchmarks use
criterion::black_box(), which is used to prevent the compiler from optimizing away computation that we're trying to time. This can be slow, though, becausecriterion::black_box()forces a point read each time it is called throughptr::road_volatile().In Rust 1.66, the standard library introduced
core::hint::black_box()(andstd::hint::black_box()). This is an intended replacement forcriterion's version that uses compiler intrinsics instead of volatile pointer reads, and thus has no runtime overhead. This increases benchmark accuracy, which is always nice 👍Note that benchmarks may appear to improve in performance after this change, but that's just because we are eliminating the pointer read overhead.
Solution
criterion::black_boxinclippy.toml.Testing
cargo clippy -p benches --benches