libm/math/
floorf.rs

1use core::f32;
2
3/// Floor (f32)
4///
5/// Finds the nearest integer less than or equal to `x`.
6#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
7pub fn floorf(x: f32) -> f32 {
8    // On wasm32 we know that LLVM's intrinsic will compile to an optimized
9    // `f32.floor` 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::floorf32(x) }
14        }
15    }
16    let mut ui = x.to_bits();
17    let e = (((ui >> 23) as i32) & 0xff) - 0x7f;
18
19    if e >= 23 {
20        return x;
21    }
22    if e >= 0 {
23        let m: u32 = 0x007fffff >> e;
24        if (ui & m) == 0 {
25            return x;
26        }
27        force_eval!(x + f32::from_bits(0x7b800000));
28        if ui >> 31 != 0 {
29            ui += m;
30        }
31        ui &= !m;
32    } else {
33        force_eval!(x + f32::from_bits(0x7b800000));
34        if ui >> 31 == 0 {
35            ui = 0;
36        } else if ui << 1 != 0 {
37            return -1.0;
38        }
39    }
40    f32::from_bits(ui)
41}
42
43// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
44#[cfg(not(target_arch = "powerpc64"))]
45#[cfg(test)]
46mod tests {
47    use core::f32::*;
48
49    use super::*;
50
51    #[test]
52    fn sanity_check() {
53        assert_eq!(floorf(0.5), 0.0);
54        assert_eq!(floorf(1.1), 1.0);
55        assert_eq!(floorf(2.9), 2.0);
56    }
57
58    /// The spec: https://en.cppreference.com/w/cpp/numeric/math/floor
59    #[test]
60    fn spec_tests() {
61        // Not Asserted: that the current rounding mode has no effect.
62        assert!(floorf(NAN).is_nan());
63        for f in [0.0, -0.0, INFINITY, NEG_INFINITY].iter().copied() {
64            assert_eq!(floorf(f), f);
65        }
66    }
67}
libm/math/floorf.rs

libm/math/
floorf.rs
