It seems like Visual Studio 17.11.5 (and toolset 14.41) added /arch:SSE4.2
.
Not very many SSE 4.2 instructions are used, on par with the old undocumented /d2archSSE42
, but it's also getting documented: https://learn.microsoft.com/en-us/cpp/build/reference/arch-x64?view=msvc-170