No, autovectorization is a lie and doesn't work. We're not stupid, we did it the way the article does it for a reason.
The main problems preventing it from working are that the compiler doesn't have enough information about alignment (especially if it's intentionally unaligned) or aliasing.
It tends to get things especially wrong when it autovectorizes code that was already partly hand vectorized; it ends up emitting the preludes (which correct for misalignment) twice.
It does work better for languages like Fortran made for it - contrary to popular belief C is not actually a low level language and isn't that easy to optimize.
It’s been a while (10 years?) since I wrote NEON and vf code (different arch but sentiment remains) and every now and then I used to run a quick disassembly to verify that my optimisation hadn’t been undone by the compiler. The first time it happens you kinda lose faith in the compiler.
There's (at least) two vectorisers in LLVM. One does loops, the other acts on basic blocks. https://llvm.org/docs/Vectorizers.html#the-slp-vectorizer. Both really like alignment metadata on pointers. They certainly have limitations but the hit rate is reasonably good.
