Vectorizing by hand is not very difficult, but even for moderately complex loops it gets tiresome very quickly. And that is before considering loop peeling for vector alignment, adding both vector and scalar remainder loops and loop multiversioning.

This is really something you want your compiler to take care of. And that indeed is something icc excels at. You just don't have to care about code size, because that _will_ grow, big time.

And no, Intel's new LLVM-based icx compiler is not at the same level yet as the (now 'classic') icc compiler.