No one currently is using very, I mean extremely old computers. The windows build can use SSE2 and i686 introduction and no one will have any problem. It's a speed problem and hat's why people is saying that xz is slower than 7zip
You would be surprised how old hardware people still use for some things.
Going from i486 instructions to i586 doesn't give anything useful for XZ Utils. Going to i686 gives cmov which can help a little. MMX and SSE/SSE2 don't help XZ Utils.
It's easy to add an i686 version into the Windows package. I doubt that alone would explain the difference to 7-Zip though. Someone could benchmark it, I don't have time now.
I very quickly tested -march=i486 vs. -march=i686, both with -mtune=generic. Maybe it speeds xz up by almost 1 % or maybe it doesn't; the results were not clear. It could be good to test more. x86-64 version seemed to be at least 10 % faster than i486 or i686 version.
I didn't include i686 version to Windows packages of XZ Utils 5.0.2 because the quick testing didn't show a clear difference to i486 version.
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