dispatch_once calls on every load from it
Performance improvements, as reported by the perf testing buildbot:
Histogram -18.81%
TwoSum -17.42%
RGBHistogram -9.65%
Regressions:
InsertionSort 5.59%
ArrayOfRef 3.99%
SwiftStructuresInsertionSort 5.29%
PrimeNum 6.09%
These regressions are bogus. The tests that "regressed" don't do any
hashing at all.
Swift SVN r23995