libm/math/
rint.rs

1#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
2pub fn rint(x: f64) -> f64 {
3    let one_over_e = 1.0 / f64::EPSILON;
4    let as_u64: u64 = x.to_bits();
5    let exponent: u64 = as_u64 >> 52 & 0x7ff;
6    let is_positive = (as_u64 >> 63) == 0;
7    if exponent >= 0x3ff + 52 {
8        x
9    } else {
10        let ans = if is_positive {
11            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
12            let x = force_eval!(x);
13            let xplusoneovere = x + one_over_e;
14            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
15            let xplusoneovere = force_eval!(xplusoneovere);
16            xplusoneovere - one_over_e
17        } else {
18            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
19            let x = force_eval!(x);
20            let xminusoneovere = x - one_over_e;
21            #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
22            let xminusoneovere = force_eval!(xminusoneovere);
23            xminusoneovere + one_over_e
24        };
25
26        if ans == 0.0 {
27            if is_positive {
28                0.0
29            } else {
30                -0.0
31            }
32        } else {
33            ans
34        }
35    }
36}
37
38// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
39#[cfg(not(target_arch = "powerpc64"))]
40#[cfg(test)]
41mod tests {
42    use super::rint;
43
44    #[test]
45    fn negative_zero() {
46        assert_eq!(rint(-0.0_f64).to_bits(), (-0.0_f64).to_bits());
47    }
48
49    #[test]
50    fn sanity_check() {
51        assert_eq!(rint(-1.0), -1.0);
52        assert_eq!(rint(2.8), 3.0);
53        assert_eq!(rint(-0.5), -0.0);
54        assert_eq!(rint(0.5), 0.0);
55        assert_eq!(rint(-1.5), -2.0);
56        assert_eq!(rint(1.5), 2.0);
57    }
58}