Question

Question: For each function call, show the contents of the stack after the function call is made. Assume the stack pointer is originally at address 0x7ff ff ff c, and follow the register conventions as specified in Figure 2.11.

Short answer

Considering the MIPS code of 231 , after calling the function fib:

$sp-> 0x7ffffffc

$sp-> #Contents of $ra

$sp-> #Contents of $s0

$sp-> -12 #Contents of $a0

There will be N-1 copies of $ra, $s0, and $a0

Step-by-step solution

Determine the MIPS instruction for a procedure and the registers used for procedure.

MIPS code for the procedure must have the following aspects:

• Control of the program should be transferred to the procedure.

• Acquire the needed storage for the procedure.

• Place the result in the accessible part

• Always return control to the point of origin.

The register used for procedure calling is as follows:

$a0-$a3- Argument register that is used to pass parameters to the functions.

$v0-$v1- value registers to which values are returned.

$ra is the return address register to return to the point of origin.

Determine the contents of the stack after the function call.

MIPS code: Refer 2.31

fib: addi $sp, $sp, -12

sw $ra, 8($sp)

sw $s0, 4($sp)

sw $a0, 0($sp)

bgt $a0, $0, test2

add $v0, $0, $0

j rtn

test2: addi $t0, $0, 1

bne $t0, $a0, gen

add $v0, $0, $t0

j rtn

gen: subi $a0, $a0,1

al fib

add $s0, $v0, $0

sub $a0, $a0,1

jal fib

add $v0, $v0, $s0

rtn: lw $a0, 0($sp)

lw $s0, 4($sp)

lw $ra, 8($sp)

addi $sp, $sp,

jr $ra

Given that the stack pointer is originally at 0x7ffffffc

The contents of the stack after the function call are:

$sp-> 0x7ffffffc

$sp-> $-4$ #Contents of $ra

$sp-> $-8$. #Contents of $s0

$sp-> -12….#Contents of $a0

There will be N-1 copies of $ra, $s0, and $a0