Is _mm_broadcast_ss faster than _mm_set1_ps?

Question

Is this code

float a = ...;
__m256 b = _mm_broadcast_ss(&a)

always faster than this code

float a = ...;
_mm_set1_ps(a)         


        

Answer 1

If you target AVX instruction set, gcc will use VBROADCASTSS to implement _mm_set1_ps intrinsic. Clang, however, will use two instructions (VMOVSS + VPSHUFD).