p2_tns4616.s

/******************************************************************************
* @file p2_tns4616.s
* @computing number of integer partitions for a positive integer
*  n with parts up to m
* @author Tanmay Sardesai, 1001094616
******************************************************************************/
 
    .global main
    .func main

main:
	BL _prompt
	BL _scanf
	MOV R4,R0
	BL _prompt
	BL _scanf
	MOV R5,R0
	MOV R1,R4
	MOV R2,R5
	MOV R7,#0
	MOV R0,#0
	BL _count_partition
	ADD R0,R0,R7
	MOV R1,R0
	MOV R2,R4
	MOV R3,R5
	BL _print_val
	B main

_print_val:
	PUSH {LR}	          	@ store LR since printf call overwrites
	LDR R0,=result_str  		@ string at label resultstr:    
	BL printf           		@ call printf, where R1 is the print argument
	POP {LR}
	MOV PC, LR	          	@ return

_prompt:
	MOV R7, #4              @ write syscall, 4
	MOV R0, #1              @ output stream to monitor, 1
	MOV R2, #17             @ print string length
	LDR R1, =prompt_str    @ string at label prompt_str:
	SWI 0                   @ execute syscall
	MOV PC, LR              @ return

_scanf:
	PUSH {LR}              @ store LR since scanf call overwrites
	SUB SP, SP, #4          @ make room on stack
	LDR R0, =format_str     @ R0 contains address of format string
	MOV R1, SP              @ move SP to R1 to store entry on stack
	BL scanf                @ call scanf
	LDR R0, [SP]            @ load value at SP into R0
	ADD SP, SP, #4          @ restore the stack pointer	
	POP {LR}    
	MOV PC, LR              @ return 

_count_partition:
	PUSH {LR}		@ Push LR onto the stack
	CMP R1,#0		@ compare R1 to #0
	MOVEQ R0,#1		@ set R0 to #1 if equal
	POPEQ {PC}		@ POP to PC from stack if equal

	MOVLT R0,#0		@ set R0 to #0 if less than
	POPLT {PC}		@ POP to PC from stack if less than

	CMP R2,#0		@ compare R2 to #0
	MOVEQ R0,#0		@ set R0 to #0 if equal
	POPEQ {PC}		@ POP to PC from stack if equal

	PUSH {R1}		@ PUSH R1 to stack
	PUSH {R2}		@ PUSH R2 to stack
	SUB R1,R1,R2		@ Subtract R2 from R1
	BL _count_partition	@ Branch with linker to _count_partition (First recurssion)
	ADD R7,R7,R0		@ Add return from count to R7
	POP {R2}		@ POP to register R2
	POP {R1}		@ POP to register R1
	SUB R2,R2,#1		@ Subract 1 from R2
	BL _count_partition	@ Branch with linker to _count_partition (Second recurssion)
	POP {PC}		@ Pop to PC from stack


	
	


.data
prompt_str:     .ascii      "Enter a number : "
format_str:		.asciz		"%d"
result_str:		.asciz 		"There are %d partitions of %d using integers up to %d\n"