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)]
fabs(x: f64) -> f647  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]
sanity_check()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]
spec_tests()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