1 | use 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)] |
7 | pub 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)] |
20 | mod 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 | } |
42 | |