trunc.rs - source
Description: Source of the Rust file `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.6/src/math/trunc.rs`.
Keywords: rust, rustlang, rust-lang

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    use core::f64;

    #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
    pub fn trunc(x: f64) -> f64 {
        // On wasm32 we know that LLVM's intrinsic will compile to an optimized
        // `f64.trunc` native instruction, so we can leverage this for both code size
        // and speed.
        llvm_intrinsically_optimized! {
            #[cfg(target_arch = "wasm32")] {
                return unsafe { ::core::intrinsics::truncf64(x) }
            }
        }
        let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120f === 2 ^ 120

        let mut i: u64 = x.to_bits();
        let mut e: i64 = (i >> 52 & 0x7ff) as i64 - 0x3ff + 12;
        let m: u64;

        if e >= 52 + 12 {
            return x;
        }
        if e < 12 {
            e = 1;
        }
        m = -1i64 as u64 >> e;
        if (i & m) == 0 {
            return x;
        }
        force_eval!(x + x1p120);
        i &= !m;
        f64::from_bits(i)
    }

    #[cfg(test)]
    mod tests {
        #[test]
        fn sanity_check() {
            assert_eq!(super::trunc(1.1), 1.0);
        }
    }