sm05-0

    .data
    .global R
R:
    .space 4

    .text
    .global calculate
calculate:
    push {r4, r5, r6, r7, r8}
    ldr r0, .Lexterns
    ldr r0, [r0]
    ldr r1, .Lexterns+4
    ldr r1, [r1]
    ldr r2, .Lexterns+8
    ldr r2, [r2]
    ldr r3, .Lexterns+12
    ldr r3, [r3]
    mul r5, r0, r1
    mul r6, r2, r3
    add r7, r5, r6
    ldr r8, .Lexterns+16
    str r7, [r8]
    pop {r4, r5, r6, r7, r8}
    bx lr
.Lexterns:
    .word A
    .word B
    .word C
    .word D
    .word R