rust/library/compiler-builtins/libm/crates/libm-test/benches/random.rs

use std::hint::black_box;
use std::time::Duration;

use criterion::{Criterion, criterion_main};
use libm_test::gen::{CachedInput, random};
use libm_test::{CheckBasis, CheckCtx, GenerateInput, MathOp, TupleCall};

/// Benchmark with this many items to get a variety
const BENCH_ITER_ITEMS: usize = if cfg!(feature = "short-benchmarks") { 50 } else { 500 };

/// Extra parameters we only care about if we are benchmarking against musl.
#[allow(dead_code)]
struct MuslExtra<F> {
    musl_fn: Option<F>,
    skip_on_i586: bool,
}

macro_rules! musl_rand_benches {
    (
        fn_name: $fn_name:ident,
        fn_extra: $skip_on_i586:expr,
    ) => {
        paste::paste! {
            fn [< musl_bench_ $fn_name >](c: &mut Criterion) {
                type Op = libm_test::op::$fn_name::Routine;

                #[cfg(feature = "build-musl")]
                let musl_extra = MuslExtra {
                    musl_fn: Some(musl_math_sys::$fn_name as <Op as MathOp>::CFn),
                    skip_on_i586: $skip_on_i586
                };

                #[cfg(not(feature = "build-musl"))]
                let musl_extra = MuslExtra {
                    musl_fn: None,
                    skip_on_i586: $skip_on_i586
                };

                bench_one::<Op>(c, musl_extra);
            }
        }
    };
}

fn bench_one<Op>(c: &mut Criterion, musl_extra: MuslExtra<Op::CFn>)
where
    Op: MathOp,
    CachedInput: GenerateInput<Op::RustArgs>,
{
    let name = Op::NAME;

    let ctx = CheckCtx::new(Op::IDENTIFIER, CheckBasis::Musl);
    let benchvec: Vec<_> =
        random::get_test_cases::<Op::RustArgs>(&ctx).take(BENCH_ITER_ITEMS).collect();

    // Perform a sanity check that we are benchmarking the same thing
    // Don't test against musl if it is not available
    #[cfg(feature = "build-musl")]
    for input in benchvec.iter().copied() {
        use anyhow::Context;
        use libm_test::CheckOutput;

        if cfg!(x86_no_sse) && musl_extra.skip_on_i586 {
            break;
        }

        let musl_res = input.call(musl_extra.musl_fn.unwrap());
        let crate_res = input.call(Op::ROUTINE);

        crate_res.validate(musl_res, input, &ctx).context(name).unwrap();
    }

    #[cfg(not(feature = "build-musl"))]
    let _ = musl_extra; // silence unused warnings

    /* Option pointers are black boxed to avoid inlining in the benchmark loop */

    let mut group = c.benchmark_group(name);
    group.bench_function("crate", |b| {
        b.iter(|| {
            let f = black_box(Op::ROUTINE);
            for input in benchvec.iter().copied() {
                input.call(f);
            }
        })
    });

    // Don't test against musl if it is not available
    #[cfg(feature = "build-musl")]
    {
        let musl_fn = musl_extra.musl_fn.unwrap();
        group.bench_function("musl", |b| {
            b.iter(|| {
                let f = black_box(musl_fn);
                for input in benchvec.iter().copied() {
                    input.call(f);
                }
            })
        });
    }
}

libm_macros::for_each_function! {
    callback: musl_rand_benches,
    skip: [],
    fn_extra: match MACRO_FN_NAME {
        // FIXME(correctness): wrong result on i586
        exp10 | exp10f | exp2 | exp2f => true,
        _ => false
    }
}

macro_rules! run_callback {
    (
        fn_name: $fn_name:ident,
        extra: [$criterion:ident],
    ) => {
        paste::paste! {
            [< musl_bench_ $fn_name >](&mut $criterion)
        }
    };
}

pub fn musl_random() {
    let mut criterion = Criterion::default();

    // For CI, run a short 0.5s warmup and 1.0s tests. This makes benchmarks complete in
    // about the same time as other tests.
    if cfg!(feature = "short-benchmarks") {
        criterion = criterion
            .warm_up_time(Duration::from_millis(500))
            .measurement_time(Duration::from_millis(1000));
    }

    criterion = criterion.configure_from_args();

    libm_macros::for_each_function! {
        callback: run_callback,
        extra: [criterion],
    };
}

criterion_main!(musl_random);