1 #![allow(unreachable_code)]
2 use core::f64;
3
4 const TOINT: f64 = 1. / f64::EPSILON;
5
6 /// Ceil (f64)
7 ///
8 /// Finds the nearest integer greater than or equal to `x`.
9 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
ceil(x: f64) -> f6410 pub fn ceil(x: f64) -> f64 {
11 // On wasm32 we know that LLVM's intrinsic will compile to an optimized
12 // `f64.ceil` native instruction, so we can leverage this for both code size
13 // and speed.
14 llvm_intrinsically_optimized! {
15 #[cfg(target_arch = "wasm32")] {
16 return unsafe { ::core::intrinsics::ceilf64(x) }
17 }
18 }
19 #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
20 {
21 //use an alternative implementation on x86, because the
22 //main implementation fails with the x87 FPU used by
23 //debian i386, probablly due to excess precision issues.
24 //basic implementation taken from https://github.com/rust-lang/libm/issues/219
25 use super::fabs;
26 if fabs(x).to_bits() < 4503599627370496.0_f64.to_bits() {
27 let truncated = x as i64 as f64;
28 if truncated < x {
29 return truncated + 1.0;
30 } else {
31 return truncated;
32 }
33 } else {
34 return x;
35 }
36 }
37 let u: u64 = x.to_bits();
38 let e: i64 = (u >> 52 & 0x7ff) as i64;
39 let y: f64;
40
41 if e >= 0x3ff + 52 || x == 0. {
42 return x;
43 }
44 // y = int(x) - x, where int(x) is an integer neighbor of x
45 y = if (u >> 63) != 0 {
46 x - TOINT + TOINT - x
47 } else {
48 x + TOINT - TOINT - x
49 };
50 // special case because of non-nearest rounding modes
51 if e < 0x3ff {
52 force_eval!(y);
53 return if (u >> 63) != 0 { -0. } else { 1. };
54 }
55 if y < 0. {
56 x + y + 1.
57 } else {
58 x + y
59 }
60 }
61
62 #[cfg(test)]
63 mod tests {
64 use super::*;
65 use core::f64::*;
66
67 #[test]
sanity_check()68 fn sanity_check() {
69 assert_eq!(ceil(1.1), 2.0);
70 assert_eq!(ceil(2.9), 3.0);
71 }
72
73 /// The spec: https://en.cppreference.com/w/cpp/numeric/math/ceil
74 #[test]
spec_tests()75 fn spec_tests() {
76 // Not Asserted: that the current rounding mode has no effect.
77 assert!(ceil(NAN).is_nan());
78 for f in [0.0, -0.0, INFINITY, NEG_INFINITY].iter().copied() {
79 assert_eq!(ceil(f), f);
80 }
81 }
82 }
83