A.5.198 PADDQ: Add Packed Quadword Integers
PADDQ mm1,mm2/m64 ; 0F D4 /r [PENT,MMX]
PADDQ xmm1,xmm2/m128 ; 66 0F D4 /r [WILLAMETTE,SSE2]
PADDQ adds the quadwords in the source and destination operands, and
stores the result in the destination register.
When an individual result is too large to fit in its destination, it
is wrapped around and the low bits are stored, with the carry bit
discarded.