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AES-NI Random Number Generator

Michael Kuron requested to merge philox into master

I was looking at how to vectorize the Philox RNG yesterday. Before I knew it, I had implemented a working RNG using AES-NI instructions 🤓 ... Not entirely what I had intended to do, but it might still be useful to someone and should be similarly fast as a vectorized Philox.

There is one place that could be optimized because I fall back to scalar instructions: I failed to reimplement _mm_cvtepu64_pd (the solution from produces incorrect results in the least-significant half of the mantissa). Perhaps someone else can try to fix that.

I did not integrate this with the vector_instruction_set parameter of the code generation. Perhaps you can do that, @bauer. It needs support for SSE2 and AES instructions (which look like SSE2 instructions, but their availability is determined by a separate CPUID flag). It will also make use of _mm_cvtepu32_ps and _mm_cvtepu64_pd from AVX512 if available (these are 128-bit instructions that actually look like SSE2 instructions).

Edited by Michael Kuron

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