A.5.200 PADDSIW: MMX Packed Addition to Implicit Destination
PADDSIW mmxreg,r/m64 ; 0F 51 /r [CYRIX,MMX]
PADDSIW, specific to the Cyrix extensions to the MMX instruction set,
performs the same function as PADDSW, except that the result is placed
in an implied register.
To work out the implied register, invert the lowest bit in the
register number. So PADDSIW MM0,MM2 would put the result in MM1, but
PADDSIW MM1,MM2 would put the result in MM0.