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 { if is_positive { 0.0 } else { -0.0 } } else { ans }
27    }
28}
29
30// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
31#[cfg(not(target_arch = "powerpc64"))]
32#[cfg(test)]
33mod tests {
34    use super::rint;
35
36    #[test]
37    fn negative_zero() {
38        assert_eq!(rint(-0.0_f64).to_bits(), (-0.0_f64).to_bits());
39    }
40
41    #[test]
42    fn sanity_check() {
43        assert_eq!(rint(-1.0), -1.0);
44        assert_eq!(rint(2.8), 3.0);
45        assert_eq!(rint(-0.5), -0.0);
46        assert_eq!(rint(0.5), 0.0);
47        assert_eq!(rint(-1.5), -2.0);
48        assert_eq!(rint(1.5), 2.0);
49    }
50}