Processor and program translation apparatus

A processor detects a function which includes no function call instruction and no update of the return address/calculation register from an assembler program. After the detection, the processor outputs a special return address to the end of the function detected, and executes the assembler program. The processor stores a return address not only on the stack but in the return address/calculation register. When the special return instruction has been fetched, the return address is moved from the return address/calculation register without accessing to the stack.