example_mips.s

.globl main

.text
main:
    addi $a0, $a0, -3               # a0 = -3
    addi $a1, $a1, 4                # a1 = 4
    addi $a2, $a2, 5                # a2 = 5
    addi $a3, $a3, 8                # a3 = 8

    jal f                           # f(a0, a1, a2, a3)

    move $a0, $v0                   # a0 = v0
    li $v0, 1                       # print int
    syscall

    li $v0, 10                      # exit
    syscall

# NOTE: doesn't save ra because it
# doesn't call any other function
# fn g(a0: int, a1: int) -> (v0: int)
#     return (|a0| - |a1|) ^ 2
g:
    subi $sp, $sp, 8                # sp -= 8
    sw $a1, 4($sp)                  # mem[sp] = a1
    sw $a0, 0($sp)                  # mem[sp] = a0

    abs $a0, $a0                    # a0 = |a0|
    abs $a1, $a1                    # a1 = |a1|  
    sub $v0, $a0, $a1               # v0 = a0 - a1
    mul $v0, $v0, $v0               # v0 *= v0

    lw $a0, 0($sp)                  # a0 = mem[sp + 0]
    lw $a1, 4($sp)                  # a1 = mem[sp + 4]
    addi $sp, $sp, 8                # sp += 8

    jr $ra

# fn f(a0: int, a1: int, a2: int, a3: int) -> (v0: int)
#     return (g(a0) + g(a1)) / 2
f:
    subi $sp, $sp, 20               # sp += 20
    sw $s0, 16($sp)                 # mem[sp + 16] = s0
    sw $a1, 12($sp)                 # mem [sp + 12] = a1
    sw $a0, 8($sp)                  # mem[sp + 8] = a1
    sw $fp, 4($sp)                  # mem[sp + 4] = fp
    sw $ra, 0($sp)                  # mem[sp + 0] = ra

    jal g                           # g(a0, a1)

    move $s0, $v0                   # s0 = v0
    move $a0, $a2                   # a0 = a2
    move $a1, $a3                   # a1 = a3

    jal g                           # g(a0, a1)

    add $s0, $s0, $v0               # s0 += v0
    srl $s0, $s0, 1                 # s0 /= 2
    move $v0, $s0                   # v0 = s0

    lw $ra, 0($sp)                  # ra = mem[sp + 0]
    lw $fp, 4($sp)                  # fp = mem[sp + 4]
    lw $a0, 8($sp)                  # a0 = mem[sp + 8]
    lw $a1, 12($sp)                 # a1 = mem[sp + 12]
    lw $s0, 16($sp)                 # s0 = mem[sp + 16]
    addi $sp, $sp, 20               # sp += 20

    jr $ra