[Bug target/101248] [AVX512] The upper bits of FIXUPIMMS{S,D} should come from src1 not dest.

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101248

--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
src1 here means operands[2], dest here means operand[0] or operands[1].