Table 4: Arithmetic RTL expression types

(plus:m x y)Represents the sum of the values x and y carried out in machine mode m.
(mult:m x y)Represents the signed product of x and y in machine mode m.
(sign_extend:m x)Represents the result of sign extend the value x to machine mode m. Mode m must be an integer mode and x must have an integer mode narrower than mode m.