vendor/compiler_builtins/libm/src/math/truncf.rs

   1 use core::f32;
   2
   3 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
   4 pub fn truncf(x: f32) -> f32 {
   5     // On wasm32 we know that LLVM's intrinsic will compile to an optimized
   6     // `f32.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::truncf32(x) }
  11         }
  12     }
  13     let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120
  14
  15     let mut i: u32 = x.to_bits();
  16     let mut e: i32 = (i >> 23 & 0xff) as i32 - 0x7f + 9;
  17     let m: u32;
  18
  19     if e >= 23 + 9 {
  20         return x;
  21     }
  22     if e < 9 {
  23         e = 1;
  24     }
  25     m = -1i32 as u32 >> e;
  26     if (i & m) == 0 {
  27         return x;
  28     }
  29     force_eval!(x + x1p120);
  30     i &= !m;
  31     f32::from_bits(i)
  32 }
  33
  34 #[cfg(test)]
  35 mod tests {
  36     #[test]
  37     fn sanity_check() {
  38         assert_eq!(super::truncf(1.1), 1.0);
  39     }
  40 }