The problem isn't just whether or not it uses SIMD instructions, but avoiding redundant and unnecessary `vmov` instructions. For example, I filed a bug here: h

The problem isn't just whether or not it uses SIMD instructions, but avoiding redundant and unnecessary `vmov` instructions. For example, I filed a bug here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86625 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86625 because unless I use SIMD intrinsics, while the code is vectorized, there is a high density of unnecessary move instructions resulting in dramatically slower code. Using SIMD intrinsics in C avoids that problem.