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  1. 	.equ	INPUT_VALUE,	5
  2. 	@ Embest board specific software interrupts
  3. 	.equ	SWI_PrInt,	0x6b
  4. 	.equ	Stdout,		0x01
  5. 	.equ	SWI_Exit,	0x11
  6.  
  7. 	.text
  8. factorial:
  9. 	@ Push stack
  10. 	stmfd	sp!, {r4, lr}
  11. 	@ Store n in local variable
  12. 	mov	r4, r0
  13. 	@ branch if n > 1
  14. 	cmp	r4, #1
  15. 	bgt	factorial_recurse
  16. 	@ return 1
  17. 	mov	r0, #1
  18. 	bal	factorial_end
  19. factorial_recurse:
  20. 	@ calculate factorial(n-1)
  21. 	mov	r0, r4
  22. 	sub	r0, r0, #1
  23. 	bl	factorial
  24. 	@ multiply returned value by n
  25. 	mul	r0, r4, r0
  26. 	@ now returns n * factorial(n-1)
  27. factorial_end:
  28. 	ldmfd	sp!, {r4, lr}
  29. 	bx	lr
  30.  
  31. 	.global _start
  32. _start:
  33. 	stmfd	sp!, {lr}
  34. 	mov	r0, #INPUT_VALUE
  35. 	bl	factorial
  36.  
  37. 	@ print to stdout
  38. 	mov	r1, r0
  39. 	mov	r0, #Stdout
  40. 	swi	SWI_PrInt
  41.  
  42. 	ldmfd	sp!, {lr}
  43. @	bx	lr
  44. 	swi	SWI_Exit
Not running #stdin #stdout 0s 0KB
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https://ideone.com/GeM8j
language:
Text (text 6.10)
created:
14 years ago
visibility:
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