\ R0 := x; R1 := y
EOR       R0, R0, R1          \ R0 := (x EOR y)
EOR       R1, R1, R0          \ R1 := y EOR (x EOR y)  [== x]
EOR       R0, R0, R1          \ R0 := (x EOR y) EOR y  [== y]
                              \ R0 := y; R1 := x