Function f32x4_demote_f64x2_zero

#[target_feature(enable = "simd128")]
pub fn f32x4_demote_f64x2_zero(a: v128) -> v128

Conversion of the two double-precision floating point lanes to two lower single-precision lanes of the result. The two higher lanes of the result are initialized to zero. If the conversion result is not representable as a single-precision floating point number, it is rounded to the nearest-even representable number.