When Swift is compiled with this new algorithm, running the attached Swift file crashes with this message:
      terminated by signal SIGILL (Illegal instruction)

Things I’ve noticed in my investigation:

- The crash happens whenever the array to be sorted is 64 elements or greater, which is the cutoff for using the new merge sort
- No crash when run in debug mode
- No crash if I add a single print statement to the _merge(…) function in “stdlib/public/core/Sort.swift”
- No crash if I simplify the less-than operator implementation for Record (in the attached Swift file) to this:

    if lhs.last != rhs.last {
      return lhs.last < rhs.last
    }
    return lhs.first < rhs.first