alt Hacker NewsI made the first proposal to the C++ standard committee to introduce SIMD in 2011, before Matthias Kretz got involved with his own version (which is what became std::simd). This was based on what eventually became Eve (mentioned in the article).
Back then, it was rejected, for the same arguments that people are making today, such as not mapping to SVE well, having a separate way to express control flow etc.
There was a real alternative being considered at the time: integrating ISPC-like semantics natively in the language. Then that died out (I'm not sure why), and SIMD became trendy, so the committee was more open to doing something to show that they were keeping up with the times.
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Trying to abstract over SVE with a SIMD library is a bit of a fool's errand. The intended programming model is just too different from traditional ISAs, and there are algorithms that are nearly impossible to write efficiently for it. All the ones I've seen wrap it up as a bastardized fixed length ISA, and even ARM's own guidance basically recommends that approach.
Frankly, the length agnostic stuff is a mistake that I hope hardware designers will eventually see the light on, like delay slots.
To me it’s clear adding the ability to express intent to parallelise is the Right Thing. This is the only way the compiler can actually know what you want it to do.