https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65782
--- Comment #5 from Daniel Fruzynski <bugzi...@poradnik-webmastera.com> --- I got following link: https://stackoverflow.com/questions/53733624/is-xmm8-register-value-preserved-across-calls/53733767#53733767 Quote from it: "Any additional registers for newer instruction sets are volatile by default. This includes the upper parts of YMM0-15 and ZMM0-15 as well as ?MM16-31 if present.". So it looks that gcc should not generate .seh_savexmm for xmm16..31 at all.
