1 use core::f64;
2
3 const TOINT: f64 = 1. / f64::EPSILON;
4
5 /// Floor (f64)
6 ///
7 /// Finds the nearest integer less than or equal to `x`.
8 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
floor(x: f64) -> f649 pub fn floor(x: f64) -> f64 {
10 // On wasm32 we know that LLVM's intrinsic will compile to an optimized
11 // `f64.floor` native instruction, so we can leverage this for both code size
12 // and speed.
13 llvm_intrinsically_optimized! {
14 #[cfg(target_arch = "wasm32")] {
15 return unsafe { ::core::intrinsics::floorf64(x) }
16 }
17 }
18 let ui = x.to_bits();
19 let e = ((ui >> 52) & 0x7ff) as i32;
20
21 if (e >= 0x3ff + 52) || (x == 0.) {
22 return x;
23 }
24 /* y = int(x) - x, where int(x) is an integer neighbor of x */
25 let y = if (ui >> 63) != 0 {
26 x - TOINT + TOINT - x
27 } else {
28 x + TOINT - TOINT - x
29 };
30 /* special case because of non-nearest rounding modes */
31 if e < 0x3ff {
32 force_eval!(y);
33 return if (ui >> 63) != 0 { -1. } else { 0. };
34 }
35 if y > 0. {
36 x + y - 1.
37 } else {
38 x + y
39 }
40 }
41
42 #[cfg(test)]
43 mod tests {
44 use super::*;
45 use core::f64::*;
46
47 #[test]
sanity_check()48 fn sanity_check() {
49 assert_eq!(floor(1.1), 1.0);
50 assert_eq!(floor(2.9), 2.0);
51 }
52
53 /// The spec: https://en.cppreference.com/w/cpp/numeric/math/floor
54 #[test]
spec_tests()55 fn spec_tests() {
56 // Not Asserted: that the current rounding mode has no effect.
57 assert!(floor(NAN).is_nan());
58 for f in [0.0, -0.0, INFINITY, NEG_INFINITY].iter().copied() {
59 assert_eq!(floor(f), f);
60 }
61 }
62 }
63