A.5.147 MAXPD: Return Packed Double-Precision FP Maximum
MAXPD xmm1,xmm2/m128 ; 66 0F 5F /r [WILLAMETTE,SSE2]
MAXPD performs a SIMD compare of the packed double-precision FP numbers
from xmm1 and xmm2/mem, and stores the maximum values of each pair of
values in xmm1. If the values being compared are both zeroes, source2
(xmm2/m128) would be returned. If source2 (xmm2/m128) is an SNaN, this
SNaN is forwarded unchanged to the destination (i.e., a QNaN version of
the SNaN is not returned).