clang Apple LLVM version 9.0.0:
sort 1 count: 2980
sort 2 count: 32756
sort 3 count: 32756
sort 4 count: 32756
sort 5 count: 32756

MSVC 2017 debug:
sort 1 count: 4484
sort 2 count: 6840
sort 3 count: 6840
sort 4 count: 6840
sort 5 count: 6840

MSVC 2017 release:
sort 1 count: 4484
sort 2 count: 3420
sort 3 count: 3420
sort 4 count: 3420
sort 5 count: 3420

clang 5.0.1 win (using MSVC 2017 headers):
sort 1 count: 4484
sort 2 count: 3420
sort 3 count: 3420
sort 4 count: 3420
sort 5 count: 3420

gcc 7.1.0 win:
sort 1 count: 5964
sort 2 count: 4292
sort 3 count: 4292
sort 4 count: 4292
sort 5 count: 4292