libm/math/
fabs.rs

1use core::u64;
2
3/// Absolute value (magnitude) (f64)
4/// Calculates the absolute value (magnitude) of the argument `x`,
5/// by direct manipulation of the bit representation of `x`.
6#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
7pub fn fabs(x: f64) -> f64 {
8    // On wasm32 we know that LLVM's intrinsic will compile to an optimized
9    // `f64.abs` native instruction, so we can leverage this for both code size
10    // and speed.
11    llvm_intrinsically_optimized! {
12        #[cfg(target_arch = "wasm32")] {
13            return unsafe { ::core::intrinsics::fabsf64(x) }
14        }
15    }
16    f64::from_bits(x.to_bits() & (u64::MAX / 2))
17}
18
19#[cfg(test)]
20mod tests {
21    use super::*;
22    use core::f64::*;
23
24    #[test]
25    fn sanity_check() {
26        assert_eq!(fabs(-1.0), 1.0);
27        assert_eq!(fabs(2.8), 2.8);
28    }
29
30    /// The spec: https://en.cppreference.com/w/cpp/numeric/math/fabs
31    #[test]
32    fn spec_tests() {
33        assert!(fabs(NAN).is_nan());
34        for f in [0.0, -0.0].iter().copied() {
35            assert_eq!(fabs(f), 0.0);
36        }
37        for f in [INFINITY, NEG_INFINITY].iter().copied() {
38            assert_eq!(fabs(f), INFINITY);
39        }
40    }
41}
libm/math/fabs.rs

libm/math/
fabs.rs
