(CMPW (MOVLconst [c]) x) => (InvertFlags (CMPWconst x [int16(c)]))
(CMPB x (MOVLconst [c])) => (CMPBconst x [int8(c)])
(CMPB (MOVLconst [c]) x) => (InvertFlags (CMPBconst x [int8(c)]))

// Canonicalize the order of arguments to comparisons - helps with CSE.
(CMP(Q|L|W|B) x y) && canonLessThan(x,y) => (InvertFlags (CMP(Q|L|W|B) y x))

// Using MOVZX instead of AND is cheaper.
(AND(Q|L)const [  0xFF] x) => (MOVBQZX x)