The extend instructions, are used to convert (extend) numbers of type i32 to type i64. There are signed and unsigned versions of this instruction.

Try it


;; push an i32 onto the stack
i32.const 10

;; sign-extend from i32 to i64

;; the top item on the stack will now be the value 10 of type i64
Instruction Binary opcode
i64.extend_i32_s 0xac
i64.extend_i32_u 0xad