I am running benchmarking software that allows the use of compiler flags, so I'm trying to use a mix of various flags to find out what works best. My question is, does each version of msse have to be enabled, or does each new version have everything that the old versions had? For example, do I need -msse2 -msse3 -msse4.1 and -msse4.2, or will -msse4.2 cover all of those?
No, in general if you use e.g. -msse3 then that implies all the earlier SSE options (-msse, -msse2 in this case).