> In particular, ARM Neon's C function wrappers on SIMD instructions generally gives you a much smaller boost than if you hand code the assembly language calls.

> In particular, ARM Neon's C function wrappers on SIMD instructions generally gives you a much smaller boost than if you hand code the assembly language calls. My practical experience using intrinsics is quite the opposite. Using C + NEON or SSE intrinsics yielded a lot better performance than what my hand written assembly could. I've heard similar stories to yours from others but they were from years ago. Later versions of compilers seem to be a lot better at this. In particular, the C compilers (GCC, Clang) were able to further optimize code written using intrinsics, where using assembler code practically inhibits all compiler optimizations. While I am able to do pretty good instruction selection by hand (which the compiler wasn't very good at), what blew me away was the compiler's ability to do instruction scheduling and register allocation. I could not have matched that without spending a huge amount of time reading architecture specific optimization manuals. So I got pretty neat, readable and portable code (x86+SSE and ARM+NEON) using a single code base where I had only written some "primitive" functions using low level intrinsics. I could write nice high level code and the compiler would inline my primitive function calls and then further optimize and re-organize the instructions.