1 use core::f64;
2 
3 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
trunc(x: f64) -> f644 pub fn trunc(x: f64) -> f64 {
5     // On wasm32 we know that LLVM's intrinsic will compile to an optimized
6     // `f64.trunc` native instruction, so we can leverage this for both code size
7     // and speed.
8     llvm_intrinsically_optimized! {
9         #[cfg(target_arch = "wasm32")] {
10             return unsafe { ::core::intrinsics::truncf64(x) }
11         }
12     }
13     let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120
14 
15     let mut i: u64 = x.to_bits();
16     let mut e: i64 = (i >> 52 & 0x7ff) as i64 - 0x3ff + 12;
17     let m: u64;
18 
19     if e >= 52 + 12 {
20         return x;
21     }
22     if e < 12 {
23         e = 1;
24     }
25     m = -1i64 as u64 >> e;
26     if (i & m) == 0 {
27         return x;
28     }
29     force_eval!(x + x1p120);
30     i &= !m;
31     f64::from_bits(i)
32 }
33 
34 #[cfg(test)]
35 mod tests {
36     #[test]
sanity_check()37     fn sanity_check() {
38         assert_eq!(super::trunc(1.1), 1.0);
39     }
40 }
41