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it's not difficult to swap the pivot with the last element and have the compiler figure out it can keep pivot in register most of the time.

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I agree with the first part -- I implemented the movable std::sort for g++, and I found it very hard to convince the compiler to keep the pivot in a register (although I did write it over 10 years ago, maybe the compiler would do a better job by now!)

https://godbolt.org/z/zPWr73qjc

Here is an implementation. This should work with all types. Unfortunate I had to annotate with restrict, but a small price to pay.

I think life gets harder when you have to deal with iterators, and have to use iterator::reference (which might not be a raw C++ reference, although it almost always is in practice).

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