Function core_arch::x86::_mm_cmp_ss

pub unsafe fn _mm_cmp_ss(a: __m128, b: __m128, imm8: i32) -> __m128

This is supported on x86 and target feature avx,sse only.

Compares the lower single-precision (32-bit) floating-point element in a and b based on the comparison operand specified by imm8, store the result in the lower element of returned vector, and copies the upper 3 packed elements from a to the upper elements of returned vector.

Intel's documentation