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8faf50e0 XL |
1 | use core::u64; |
2 | ||
dc9dc135 XL |
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`. | |
48663c56 | 6 | #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
8faf50e0 | 7 | pub fn fabs(x: f64) -> f64 { |
a1dfa0c6 XL |
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 | } | |
8faf50e0 XL |
16 | f64::from_bits(x.to_bits() & (u64::MAX / 2)) |
17 | } | |
60c5eb7d XL |
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 | } |