Popcount CPU instruction

.NET Core 3 (in preview, due out Sep 23) includes support for popcount as part of the BitOperations class: https://docs.microsoft.com/en-us/dotnet/api/system.numerics..... There's a recent post describing hardware intrinsics in .NET Core: https://devblogs.microsoft.com/dotnet/hardware-intrinsics-in... There are a lot of potential use cases, but one of the early discussions was around quickly scanning for known HTTP headers. You can see that in use here…

Back in the mid-2000s I worked at a company that made their own (MIPS-based) chips. NSA was one of our customers - supposedly the "defense" who could be considered the good side of NSA compared to the 10x larger "offense" but still. As we were planning for our second generation, they offered quite a bit of money if we'd implement a "sheep and goats" instruction. It would take two operands: an input and a mask. The masked-in bits of the…

On the PS3 SPU cores, the best "does everything" instruction was the single "rotate and mask" series of instructions which was the underlying implementation of all rotates, shifts, and bitfield extraction instructions. That architecture is still my favourite years on - every register was vectorised by default, and the instruction was the minimalistic set to achieve a lot of unusual operations that were incredibly useful for graphics or signal processing work. Often you couldn't find an exact instruction to do…