1. CS41B recursion
David Kauchak CS 52 – Fall 2015

2. Admin Midterm back on Thursday Assignments Survey in assignment 4
Assignment 4: due Monday (10/12 at 11:59pm)
Assignment 5: due Friday (10/23 at 5pm)
Assignment 6: due Monday (11/2 at 11:59pm)
Survey in assignment 4
Academic Honesty

3. Academic Honesty
A few rules to follow for this course to keep you out of trouble:
If you talk with someone in the class about a problem, you should not take notes. If you understand the material you talked about, you should be able to recreate it on your own.
Similarly, if you talk with someone, you must wait 5 minutes before resuming work on the problem. Stretch. Use the restroom. Go for a quick walk. This will ensure that you really understand the material.
You may not sit next to (or where you can see the screen of) anyone you are talking with about the assignment.
The only time you may look at someone else's screen is if they are asking you for help with a basic programming problem (e.g. syntax error). You should not look at someone else's code to help yourself!

4. Examples from this lecture

5. CS41B machine CPU instruction counter (location in memory of the next
instruction in memory)
processor ic r0
holds the value 0 (read only) r1
general purpose
read/write r2
registers r3

6. Memory layout Code Heap Stack
Code
Where dynamically allocated program data is stored
Heap
Where program/function execution information is stored, parameters, and local variables
Stack

7. Stack frame Key unit for keeping track of a function call
return address (where to go when we’re done executing)
parameters
local variables

8. CS41B function call conventions
r1: reserved for the stack pointer r2: contains the return address r3: contains the first parameter additional parameters go on the stack (more on this) the result (i.e. the return value) should go in r3

9. Structure of a single parameter function
fname psh r2 ; save return address on stack ... ; do work using r3 as argument ; put result in r3 pop r2 ; restore return address from stack jmp r2 ; return to caller
conventions:
argument is in r3
r1 is off-limits since it’s used for the stack pointer
return value goes in r3

10. Our first function call
loa r3 r0 ; get variable lcw r2 increment ; call increment cal r2 r2 sto r0 r3 ; write result, hlt ; and halt increment psh r2 ; save the return address on the stack adc r3 r3 1 ; add 1 to the input parameter pop r2 ; get the return address from stack jmp r2 ; go back to where we were called from

11. Functions with multiple arguments
fname psh r2 ; save return address on stack loa r2 r1 4 ; load the second parameter into r2 ... ; do work using r3 and r2 as arguments ; put result in r3 pop r2 ; restore return address from stack jmp r2 ; return to caller
conventions:
first argument is in r3
r1 is off-limits since it’s used for the stack pointer
return value goes in r3

12. Functions with multiple arguments
fname psh r2 ; save return address on stack loa r2 r1 4 ; load the second parameter into r2 ... ; do work using r3 and r2 as arguments ; put result in r3 pop r2 ; restore return address from stack jmp r2 ; return to caller
What does this operation do? What is the 4?

13. Functions with multiple arguments
fname psh r2 ; save return address on stack loa r2 r1 4 ; load the second parameter into r2 ... ; do work using r3 and r2 as arguments ; put result in r3 pop r2 ; restore return address from stack jmp r2 ; return to caller
r1 is the stack pointer and points at the top (next) slot
stacks grow towards smaller memory values

14. Functions with multiple arguments
fname psh r2 ; save return address on stack loa r2 r1 4 ; load the second parameter into r2 ... ; do work using r3 and r2 as arguments ; put result in r3 pop r2 ; restore return address from stack jmp r2 ; return to caller
r1 is the stack pointer and points at the top (next) slot
stacks grow towards smaller memory values
r1+2 is then the top value of the stack
r1+4 is the 2nd value of the stack

15. Multiple arguments What does this code do?
max psh r2 loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif pop r2 jmp r2
What does this code do?

16. Multiple arguments max, as a function!
max psh r2 loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif pop r2 jmp r2
max, as a function!

17. Calling max
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt
Anything different?

18. Calling max For the second argument, push it on the stack
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt
For the second argument, push it on the stack

19. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 r3
sp (r1)
Stack

20. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 r3 10
sp (r1)
Stack

21. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
Stack

22. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1) 2
Stack

23. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1) 2
Stack

24. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
max r3 10
Notice that we overwrote the value in r2
If we hadn’t save it on the stack, it would have been lost
sp (r1) 2
Stack

25. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
max r3 10
sp (r1) 2
Stack

26. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1) 2
Stack

27. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1) 2
Stack

28. loc: cal 2 r2 loc: cal r3 10 sp (r1) Stack
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1)
loc: cal 2
Stack

29. loc: cal 2 r2 loc: cal r3 10 sp (r1) Stack
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1)
loc: cal 2
Stack

30. loc: cal 2 r2 loc: cal r3 10 sp (r1) larger values Stack
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1)
loc: cal +2
larger values 2 +4
Stack

31. loc: cal 2 r2 2 r3 10 sp (r1) larger values Stack
loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
loc: cal +2
larger values 2 +4
Stack

32. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
loc: cal 2
Stack

33. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
loc: cal 2
Stack

34. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1) 2
Stack

35. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1) 2
Stack

36. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2
loc: cal r3 10
sp (r1) 2
Stack

37. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
Stack

38. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
Stack

39. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
10!
sp (r1)
Stack

40. loa r3 r0 loa r2 r0 psh r2 lcw r2 max cal r2 r2 pop r2 sto r0 r3 hlt max loa r2 r1 4 bge r3 r2 endif adc r3 r2 0 endif jmp r2 r2 2 r3 10
sp (r1)
Stack

41. Real structure of CS41B program
; great comments at the top! ; lcw r1 stack instruction1 ; comment instruction2 ; comment ... hlt ; stack area: 50 words dat 100 stack end
Save address of highest end (highest address) of the stack in r1
Reserve 50 words for the stack

42. Recursion What does this function do?
int mystery(int a, int b){ if( b <= 0 ){ return 0 else return a + mystery(a, b-1) }
What does this function do?

43. Recursion Multiplication… a*b (assuming b is positive)
int mystery(int a, int b){ if( b <= 0 ){ return 0 else return a + mystery(a, b-1) }
Multiplication… a*b (assuming b is positive)
Note to future Dave from past Dave: write the function up on the board 

44. Function cleanup and return
mult psh r2 ; save the return address psh r3 ; save first argument, a, on stack loa r2 r1 6 ; get at the 2nd argument, b ; b = r2, a = r3 blt r0 r2 else ; 0 < r2, i.e. recursive case adc r3 r0 0 ; return 0 brs endif else sbc r2 r2 1 ; r2 = b-1 psh r2 ; add r2 as 2nd argument lcw r2 mult ; call mult recursively cal r2 r2 pop r2 ; pop 2nd argument off stack loa r2 r1 2 ; load a into r2 off of the stack add r3 r3 r2 ; r3 = a + mult(a, b-1) endif pop r0 ; remove first argument from stack pop r2 ; get the return address jmp r2 ; return
Function startup
Base case
Recursive case
Recursive call
answer calculation
Function cleanup and return

45. Notice symmetry of psh and pop
mult psh r2 ; save the return address psh r3 ; save first argument, a, on stack loa r2 r1 6 ; get at the 2nd argument, b ; b = r2, a = r3 blt r0 r2 else ; 0 < r2, i.e. recursive case adc r3 r0 0 ; return 0 brs endif else sbc r2 r2 1 ; r2 = b-1 psh r2 ; add r2 as 2nd argument, r3 shouldn't have changed lcw r2 mult ; call mult recursively cal r2 r2 pop r2 ; pop 2nd argument off stack loa r2 r1 2 ; load a into r2 off of the stack add r3 r3 r2 ; r3 = a + mult(a, b-1) endif pop r0 ; remove first argument from stack pop r2 ; get the return address jmp r2 ; return
Notice symmetry of psh and pop

46. Calling mult r2 r3 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

47. Calling mult r2 r3 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

48. Calling mult r2 r3 6 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

49. Calling mult r2 r3 6 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

50. Calling mult r2 2 r3 6 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

51. Calling mult r2 2 r3 6 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

52. Calling mult r2 2 r3 6 sp (r1) 2 Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1) 2
Stack

53. Calling mult r2 2 r3 6 sp (r1) 2 Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1) 2
Stack

54. Calling mult r2 loc: mult r3 6 sp (r1) 2 Stack loa r3 r0 loa r2 r0
psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1) 2
Stack

55. Calling mult r2 loc: mult r3 6 sp (r1) 2 Stack loa r3 r0 loa r2 r0
psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1) 2
Stack

56. r2 loc: cal0 r3 6 sp (r1) 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1) 2
Stack

57. r2 loc: cal0 r3 6 sp (r1) 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1) 2
Stack

58. r2 loc: cal0 r3 6 sp (r1) loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1)
loc: cal0 2
Stack

59. r2 loc: cal0 r3 6 sp (r1) loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1)
loc: cal0 2
Stack

60. r2 loc: cal0 r3 6 Why push r3? sp (r1) 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
Why push r3?
sp (r1) 6
loc: cal0 2
Stack

61. mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
Not always required, but allows us to use r3 for computation without worrying about losing first parameter
sp (r1) 6
loc: cal0 2
Stack

62. r2 loc: cal0 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1) 6
loc: cal0 2
Stack

63. r2 loc: cal0 r3 6 sp (r1) 6 loc: cal0 larger values 2 Stack +2 +4 +6
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 6
sp (r1) 6 +2
loc: cal0 +4
larger values 2 +6
Stack

64. r2 2 r3 6 sp (r1) 6 loc: cal0 larger values 2 Stack +2 +4 +6 mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 2 r3 6
sp (r1) 6 +2
loc: cal0 +4
larger values 2 +6
Stack

65. r2 2 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
jmp r2 r2 2 r3 6
sp (r1) 6
loc: cal0 2
Stack

66. r2 2 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 2 r3 6
sp (r1) 6
loc: cal0 2
Stack

67. r2 1 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal0 2
Stack

68. r2 1 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal0 2
Stack

69. r2 1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

70. r2 1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

71. r2 loc: mult r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: mult r3 6
sp (r1) 1 6
loc: cal0 2
Stack

72. r2 loc: mult r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: mult r3 6
sp (r1) 1 6
loc: cal0 2
Stack

73. r2 loc: cal1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

74. r2 loc: cal1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

75. r2 loc: cal1 r3 6 sp (r1) loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1)
loc: cal1 1 6
loc: cal0 2
Stack

76. r2 loc: cal1 r3 6 sp (r1) loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1)
loc: cal1 1 6
loc: cal0 2
Stack

77. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

78. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

79. r2 1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

80. r2 1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

81. r2 1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

82. r2 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

83. r2 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

84. r2 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

85. r2 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

86. r2 loc: mult r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: mult r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

87. r2 loc: mult r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: mult r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

88. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

89. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

90. r2 loc: cal1 r3 6 sp (r1) loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1)
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

91. r2 loc: cal1 r3 6 sp (r1) loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1)
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

92. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

93. r2 loc: cal1 r3 6 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

94. r2 r3 6 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

95. r2 r3 6 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

96. r2 r3 6 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3 6
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

97. r2 r3 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

98. r2 r3 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

99. r2 r3 Stack frames! sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
Stack frames!
sp (r1) 6
loc: cal1
mult(6,0) 6
loc: cal1
mult(6,1) 1 6
loc: cal0
mult(6,2) 2
Stack

100. r2 r3 sp (r1) 6 loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1) 6
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

101. r2 r3 sp (r1) loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
We don’t actually care about this value, but need to get it off the stack to cleanup… just put it in r0, which throws it away
sp (r1)
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

102. r2 r3 sp (r1) loc: cal1 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1)
loc: cal1 6
loc: cal1 1 6
loc: cal0 2
Stack

103. r2 loc: cal1 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

104. r2 loc: cal1 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

105. Returning with answer in r3
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack
Returning with answer in r3

106. r2 loc: cal1 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

107. r2 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

108. r2 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

109. r2 6 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

110. r2 6 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

111. r2 6 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

112. r2 6 r3 sp (r1) 6 loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal1 1 6
loc: cal0 2
Stack

113. r2 6 r3 sp (r1) loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1)
loc: cal1 1 6
loc: cal0 2
Stack

114. r2 6 r3 sp (r1) loc: cal1 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1)
loc: cal1 1 6
loc: cal0 2
Stack

115. r2 loc: cal1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

116. r2 loc: cal1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

117. Returning with answer in r3
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack
Returning with answer in r3

118. r2 loc: cal1 r3 6 sp (r1) 1 6 loc: cal0 2 Stack mult psh r2 psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal1 r3 6
sp (r1) 1 6
loc: cal0 2
Stack

119. r2 1 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal0 2
Stack

120. r2 1 r3 6 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 1 r3 6
sp (r1) 6
loc: cal0 2
Stack

121. r2 6 r3 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal0 2
Stack

122. r2 6 r3 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3
sp (r1) 6
loc: cal0 2
Stack

123. r2 6 r3 12 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3 12
sp (r1) 6
loc: cal0 2
Stack

124. r2 6 r3 12 sp (r1) 6 loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3 12
sp (r1) 6
loc: cal0 2
Stack

125. r2 6 r3 12 sp (r1) loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3 12
sp (r1)
loc: cal0 2
Stack

126. r2 6 r3 12 sp (r1) loc: cal0 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2 6 r3 12
sp (r1)
loc: cal0 2
Stack

127. r2 loc: cal0 r3 12 sp (r1) 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 12
sp (r1) 2
Stack

128. r2 loc: cal0 r3 12 sp (r1) 2 Stack mult psh r2 psh r3 loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 12
sp (r1) 2
Stack

129. Returning with answer in r3
mult
psh r2
psh r3
loa r2 r1 6
blt r0 r2 else
adc r3 r0 0
brs endif
else
sbc r2 r2 1
lcw r2 mult
cal r2 r2
pop r2
loa r2 r1 2
add r3 r3 r2
endif
pop r0
jmp r2 r2
loc: cal0 r3 12
sp (r1) 2
Stack
Returning with answer in r3

130. Calling mult r2 loc: cal0 r3 12 sp (r1) 2 Stack loa r3 r0 loa r2 r0
psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1) 2
Stack

131. Calling mult r2 2 r3 12 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

132. Calling mult r2 2 r3 12 sp (r1) Stack loa r3 r0 loa r2 r0 psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
sp (r1)
Stack

133. Calling mult r2 2 r3 12 Print the answer: 12! sp (r1) Stack loa r3 r0
psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
Print the answer: 12!
sp (r1)
Stack

134. Calling mult r2 2 r3 12 Print the answer: 12! sp (r1) Stack loa r3 r0
psh r2
lcw r2 mult
cal r2 r2
pop r2
sto r0 r3
hlt
Print the answer: 12!
sp (r1)
Stack

135. Run mult.a41 in simulator

136. CS41B programming advice
Match your push and pops
Follow the register conventions
Develop code incrementally
Debugging: write out stack, registers, etc. on paper and compare against system execution

137. Examples from this lecture