Question

Consider the function with header: int foo(int s, int n, int a, int b).

Write MIPS assembly code for the following statement located inside the above function:
return(s+n);

Answer 1

MIPS code for function 'foo'

foo:

add $v0, $a0, $a1

jr $ra

-------------------------------

EXPLANATION:

When function 'foo' is invoked, the following instructions are executed:

1. add $v0, $a0, $a1 :

• Register $a0 stores the first argument i.e., a0= s
• & Register $a1 stores the second argument i.e, a1=n
• add instruction adds the values in $a0 and $a1 and saves the result in register $v0.
• The value stored in register $v0 is the one to be returned from the function.

2. jr $ra

• Instruction is used to jump to the location that called the function 'foo'.