How to write a If, Else if in assembly - c

Question

I need to convert the following C code to its equivalent in Assembly. I've only taken a few classes on assembly and don't really have a grasp of the language yet.
int x = 45
int y = 27
while (x != y) {
if (x > y)
x = x - y;
else if (y > x)
y = y - x;
}
return x; // Sends exit code containing GCD
I have written what i believe to work and am about to use a debugger to find inevitable flaws but wanted to ask if i am headed in the right direction with the if else statement.
.global _start
_start
mov R1, #45 #R1 = 45
mov R2, #27 #R2 = 27
loopTop:
cmp R1, R2
beq allDone
bge R1,R2
sub R1,R1,R0
bge R2,R1
sub R2,R2,R1
b loopTop
allDone:
SWI R1
Any help/tips would be greatly appreciated!
Thanks!

Answer 1

Here's your solution:
mov R1, #45 #x
mov R2, #27 #y
loop:
cmp R1, R2 #compare R1 with R2
bne label1 #is R1 not equals to R2? "Branch is Not Equal" to label1, else...
#<replace with the return R1 statement here>
label1:
cmp R1, R2
bgt sub_xy #"Branch on Greater Than"
cmp R1, R2
blt sub_yx #"Branch on Lower Than"
sub_xy:
sub R1, R1, R2 #R1 = R1 - R2
b loop #branch to loop
sub_yx:
sub R2, R2, R1 #R2 = R2 - R1
b loop
Came up with this as a newb x86_64 programmer trying to code for ARM for the first time.
EDIT: Corrections/ explanations are in the comments.