Well, yet we have a game or too which is broken with this flag in Proton (which builds i386 with -msse2 from start). For that reason there is a hack removing that flag with #pragma for ddraw.
Notice that these changes are not supposed to enable sse instructions for floating point arithmetic; that would be `-mfpmath=sse`, which is not implied by either compile option that I'm introducing here. This is quite a smaller change; the compiler is still allowed to use additional instructions in some situations (most likely for struct copies or synthesized `memcpy()`) but I don't expect it to be so impactful. As far as I can see, Proton in fact only forces the default fpmath setting for ddraw, it doesn't touch `-msse` or `-msse2` or any of that, e.g.: https://github.com/ValveSoftware/wine/commit/4912df4e37458b06f14abebb5382610.... -- https://gitlab.winehq.org/wine/wine/-/merge_requests/10953#note_140757