Question

ARM Assignment

Goals:

Initialize register X, Y, and Z to zero.

Loop 10 times, each time adding 1 to register X.

If register X is even, add one to register Y.

If register X is divisible by 3, add one to register Z.

Result:

Register X at 10.

Register Y at 5.

Register Z at 3 or 4 (depending on when you increment your counter).

Answer 1

ARM64 GCC 5.4 CODE

main:

sub sp, sp, #16

str wzr, [sp, 12]

str wzr, [sp, 8]

str wzr, [sp, 4]

.L5:

ldr w0, [sp, 12]

cmp w0, 9

bgt .L2

ldr w0, [sp, 12]

and w0, w0, 1

cmp w0, wzr

bne .L3

ldr w0, [sp, 8]

add w0, w0, 1

str w0, [sp, 8]

.L3:

ldr w2, [sp, 12]

mov w0, 21846

movk w0, 0x5555, lsl 16

smull x0, w2, w0

lsr x1, x0, 32

asr w0, w2, 31

sub w1, w1, w0

mov w0, w1

lsl w0, w0, 2

sub w0, w0, w1

sub w1, w2, w0

cmp w1, wzr

bne .L4

ldr w0, [sp, 4]

add w0, w0, 1

str w0, [sp, 4]

.L4:

ldr w0, [sp, 12]

add w0, w0, 1

str w0, [sp, 12]

b .L5

.L2:

mov w0, 0

add sp, sp, 16

ret