Function core::arch::x86_64::_mm_cvtsd_ss

pub unsafe fn _mm_cvtsd_ss(a: __m128, b: __m128d) -> __m128

This is supported on x86-64 and target feature sse2 only.

Convert the lower double-precision (64-bit) floating-point element in b to a single-precision (32-bit) floating-point element, store the result in the lower element of the return value, and copy the upper element from a to the upper element the return value.

Intel's documentation