I think it's for people like me, who recognize that depending on the dataset that a lot of performance is left on the table for some datasets when you don't take advantage of SIMD, but are not interested in becoming experts on intrinsics for a multitude of processor combinations.
Having a way to be able to say "flag bytes in this buffer matching one of these five characters, choose the appropriate stride for the actual CPU" and then "OR those flags together and do a popcount" (as I needed to do writing my own wc(1) as an exercise), and have that at least come close to optimal performance with intrinsics would be great.
Just like I'd rather use a ranged-for than to hand count an index vs. a size.
> People that don’t use SIMD today are unlikely to use std::simd tomorrow.
I mean, why not? That's exactly my use case. I don't use SIMD today as it's a PITA to do properly despite advancements in glibc and binutils to make it easier to load in CPU-specific codes. And it's a PITA to differentiate the utility of hundreds of different vpaddcfoolol instructions. But it is legitimately important for improving performance for many workloads, so I don't want to miss it where it will help.
And even gaining 60, 70% of the "optimal" SIMD still puts you much closer to highest performance that the alternative.
In the end I did end up having to write some direct SIMD intrinsics, I forget what issue I'd run into starting off with std::simd, but std::simd was what had made that problem seem approachable for the first time.