Unfortunately a C compiler isn't going to know what to do with your probably-unaligned pointer to 5 floats that you're doing mostly horizontal arithmetic on. An

Unfortunately a C compiler isn't going to know what to do with your probably-unaligned pointer to 5 floats that you're doing mostly horizontal arithmetic on. And SIMD instructions provide zero benefit if the data is spread out in memory, as is the case for most C/C++ application code. Otherwise, if you want to smack proper vectors and matrices together at high speed, libraries like Eigen or DXMath already abstract away the SIMD details and work great. For nitty-gritty stuff like codecs, that's always going to be handwritten with intrinsics (or ASM), and that's fine. And libc functions like memcpy already use the fastest, fanciest instructions. It's mostly a solved problem. Lastly, for a lot of tasks, regular math instructions are plenty fast. On modern CPUs, you need to be doing a lot of math before worrying about SIMD is worth it. And once your program becomes particularly math-heavy, you'll probably want to use the GPU instead anyways.