That vminpd+vminpd+vorpd actually does handle signed zero properly! Screws up NaN payloads to the max though. Can be easily extended to canonicalize the NaN with 2 instrs + constant though of course. (which ends up at the same number of instrs as your proper impl (albeit with worse port distribution and latency), but you get to have a canonical NaN!)

Hit upon https://github.com/llvm/llvm-project/issues/217376 while playing around with proper minimumnum, failing to SMT-verify whatever version of LLVM I had; did find a funky working 6-instr (+ constant) version though:

    vpandn      ymm2, ymm1, ymm0
    vpcmpeqd    ymm2, ymm2, 0x80000000 # whether ymm0 is -0 and ymm1 is +0 (or other cases that magically don't cause issues)
    vcmpltpd    ymm3, ymm0, ymm1
    vcmpunordpd ymm3, ymm3, ymm1 # regular NaN-is-larger ymm0<ymm1
    vpor        ymm2, ymm2, ymm3
    vpblendvb   ymm0, ymm1, ymm0, ymm2