Function core::arch::x86::_mm_cvtss_sd

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

This is supported on x86 and target feature sse2 only.

Convert the lower single-precision (32-bit) floating-point element in b to a double-precision (64-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