A.5.233 PMAXSW: Packed Signed Integer Word Maximum
PMAXSW mm1,mm2/m64 ; 0F EE /r [KATMAI,MMX]
PMAXSW xmm1,xmm2/m128 ; 66 0F EE /r [WILLAMETTE,SSE2]
PMAXSW compares each pair of words in the two source operands, and for
each pair it stores the maximum value in the destination register.