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global main
type main,"function"
p2align 4
This program will solve the Tower of Hanoi puzzle
using a recursive function.
ain:
ldr x1, =src
ldr x2, =dest
ldr x3, =aux
ldr x5, =no_discs
ldr x4,[x5]
sub sp,sp,#48 // Pushing four values and reserving a place for x30
stp x1,x2,[sp]
stp x3,x4,[sp,#16]
bl move_discs
add sp,sp,#48
bl exit
Function: move_discs
Arguments: Source,Destination,Auxiliary,Number of Discs
Purpose: To move discs recursively from the source to the
destination using the auxiliary rod.
ove_discs:
# Store x30, the return point
str x30,[sp,#32]
# Get the arguments from the stack
# into registers
ldp x1,x2,[sp]
ldp x3,x4,[sp,#16]
# First step: move all discs but the bottom one from the source to the
# auxiliary rod
# Only one disc? Print move
cmp x4,#1
b.eq print_move
# Otherwise, move the all discs except the bottom one to "aux"
sub sp,sp,#48
stp x1,x3,[sp]
sub x4,x4,#1
stp x2,x4,[sp,#16]
bl move_discs
# Upon return, restore the stack pointer
add sp,sp,#48
# Second step: move the bottom disc from the source to the destination
rint_move:
ldp x1,x2,[sp]
ldr x0,=format_string
bl printf
# Third step: move all discs but the bottom one from the Auxiliary rod to
# To the destination
#First, get the arguments from the stack to the registers
ldp x1,x2,[sp]
ldp x3,x4,[sp,#16]
# Only one disc? Return
cmp x4,#1
b.eq function_end
#Othersise, mova all remaining discs from "aux" to "dst"
sub sp,sp,#48
stp x3,x2,[sp]
sub x4,x4,#1
stp x1,x4,[sp,#16]
bl move_discs
add sp,sp,#48
unction_end:
ldr x30,[sp,#32]
ret
data
ormat_string:
.asciz "Moving from %s to %s\n"
rc:
.asciz "src"
est:
.asciz "dst"
ux:
.asciz "aux"
o_discs:
.xword 4
