Simulating a CPU with Ruby

Transcript

1. Simulating a CPU with Ruby Denis Defreyne / RUG::B / April 2, 2015 1
2. May contain nuts. 2 DISCLAIMER
3. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
4. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
5. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
6. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
7. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
8. 3 1. Write an assembler 2. Design an assembly language 3. Design a CPU instruction format 4. Design a CPU instruction set 5. Write an emulator
9. 4
10. 4
11. 4
12. 5
13. loop do 5
14. loop do grab
 5
15. loop do grab
 case apple_color 5
16. loop do grab
 case apple_color when :red 5
17. loop do grab
 case apple_color when :red move_to(:right) 5
18. loop do grab
 case apple_color when :red move_to(:right) when :green 5
19. loop do grab
 case apple_color when :red move_to(:right) when :green move_to(:left) 5
20. loop do grab
 case apple_color when :red move_to(:right) when :green move_to(:left) end
 5
21. loop do grab
 case apple_color when :red move_to(:right) when :green move_to(:left) end
 release 5
22. loop do grab
 case apple_color when :red move_to(:right) when :green move_to(:left) end
 release move_to(:middle) 5
23. loop do grab
 case apple_color when :red move_to(:right) when :green move_to(:left) end
 release move_to(:middle) end 5
24. A program is a stream of instructions. 6
25. 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
26. 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
27. grab # grab apple 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
28. grab # grab apple getcolor r0 # r0 now contains apple color 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
29. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
30. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
31. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
32. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
33. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
34. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
35. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
36. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
37. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
38. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
39. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
40. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) mvarm 0 # move arm (0 means middle) 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
41. grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) mvarm 0 # move arm (0 means middle) jmp @start # jump 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
42. start: grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) mvarm 0 # move arm (0 means middle) jmp @start # jump 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
43. start: grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) mvarm 0 # move arm (0 means middle) jmp @start # jump 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
44. start: grab # grab apple getcolor r0 # r0 now contains apple color cmp r0, 0 # 0 means red je @red # jump if equal (i.e. red) jmp @green # jump
 green: mvarm 1 # move arm (1 means left) jmp @done # jump
 red: mvarm 2 # move arm (2 means right) jmp @done # jump
 done: release # release apple (falls in target pile) mvarm 0 # move arm (0 means middle) jmp @start # jump 7 loop do grab case apple_color when :red move_to(:right) when :green move_to(:left) end release move_to(:bucket) end
45. 8
46. lv r0, 123 8
47. lv r0, 123 prn r0 8
48. lv r0, 123 prn r0 halt 8
49. prn is not a realistic instruction. 9 CHEAT #1
50. CHEAT #1 halt is not a realistic instruction. 10 CHEAT #2
51. 11
52. lv r0, 100 11
53. lv r0, 100 lv r1, 200 11
54. lv r0, 100 lv r1, 200 add r2, r0, r1 11
55. lv r0, 100 lv r1, 200 add r2, r0, r1 prn r2 11
56. lv r0, 100 lv r1, 200 add r2, r0, r1 prn r2 halt 11
57. def gcd(a, b) while b != 0 t = b b = a % b a = t end a end 12
58. 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
59. lv r0, 819000 # r0 = 819000 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
60. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
61. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
62. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
63. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
64. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
65. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
66. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 jmp @start # jump to @start
 
 
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end
67. lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 jmp @start # jump to @start
 
 
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end 
 
 
 start: 
 
 
 
 
 
 
 

68. 
 
 
 
 
 
 
 
 
 
 
 end: lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 jmp @start # jump to @start
 
 
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end 
 
 
 start: 
 
 
 
 
 
 
 

69. 
 
 
 
 
 
 
 
 
 
 
 end: prn r0 # print r0 (our gcd!) lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 jmp @start # jump to @start
 
 
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end 
 
 
 start: 
 
 
 
 
 
 
 

70. 
 
 
 
 
 
 
 
 
 
 
 end: prn r0 # print r0 (our gcd!) halt # shut down lv r0, 819000 # r0 = 819000 lv r1, 254163 # r1 = 254163
 
 cmp r1, 0 # compare r1 with 0 je @end # jump to @end if = mov r2, r1 # r2 <— r1 mod r1, r0, r1 # r1 <— r0 % r1 mov r0, r2 # r0 <— r2 jmp @start # jump to @start
 
 
 13 def gcd(r0, r1) while r1 != 0 r2 = r1 r1 = r0 % r1 r0 = r2 end r0 end 
 
 
 start: 
 
 
 
 
 
 
 

71. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 0113 0100 010f 0002 060c 0e00 ff 14
72. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 15
73. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 15
74. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 15
75. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 15
76. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 15
77. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 15
78. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 1301 0001 mod r1, r0, r1 15
79. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 1301 0001 mod r1, r0, r1 0f00 02 mov r0, r2 15
80. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 1301 0001 mod r1, r0, r1 0f00 02 mov r0, r2 060c jmp @start 15
81. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 1301 0001 mod r1, r0, r1 0f00 02 mov r0, r2 060c jmp @start 0e00 prn r0 15
82. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 1000 000c 7f38 lv r0, 819000 1001 0003 e0d3 lv r1, 254163 1201 0000 0000 cmp r1, 0 0720 je @end 0f02 01 mov r2, r1 1301 0001 mod r1, r0, r1 0f00 02 mov r0, r2 060c jmp @start 0e00 prn r0 ff halt 15
83. Machine code is executed by actual, physical CPUs. Bytecode is executed by virtual machines. 16
84. 17 YARV
85. 18 JVM
86. 0000000000001f76 <_rb_ary_freeze>: 1f76: 55 push %rbp 1f77: 48 89 e5 mov %rsp,%rbp 1f7a: 5d pop %rbp 1f7b: e9 32 b6 07 00 jmpq 7d5b2 <_rb_obj_freeze> 0000000000002483 <_rb_ary_free>: 2483: 55 push %rbp 2484: 48 89 e5 mov %rsp,%rbp 2487: 40 f6 c7 07 test $0x7,%dil 248b: 75 23 jne 24b0 <_rb_ary_free+0x2d> 248d: 48 89 f8 mov %rdi,%rax 2490: 48 83 e0 f7 and $0xfffffffffffffff7,%rax 2494: 74 1a je 24b0 <_rb_ary_free+0x2d> 2496: 48 8b 07 mov (%rdi),%rax 2499: 48 89 c1 mov %rax,%rcx 249c: 48 83 e1 1f and $0x1f,%rcx 24a0: 48 83 f9 1c cmp $0x1c,%rcx 24a4: 74 0a je 24b0 <_rb_ary_free+0x2d> 24a6: 48 25 00 60 00 00 and $0x6000,%rax 24ac: 74 02 je 24b0 <_rb_ary_free+0x2d> 24ae: 5d pop %rbp 24af: c3 retq 24b0: 48 8b 7f 20 mov 0x20(%rdi),%rdi 24b4: 5d pop %rbp 24b5: e9 23 39 04 00 jmpq 45ddd <_ruby_xfree> 19 X86
87. 0010c00 <main.init.1>: 10c00: e59a1008 ldr r1, [sl, #8] 10c04: e15d0001 cmp sp, r1 10c08: 91a0300e movls r3, lr 10c0c: 9b01a46b blls 79dc0 <runtime.morestack_noctxt> 10c10: 9afffffa bls 10c00 <main.init.1> 10c14: e52de044 str lr, [sp, #-68]! ; 0xffffffbc 10c18: e59fb19c ldr fp, [pc, #412] ; 10dbc <main.init.1+0x1bc> 10c1c: e5db0000 ldrb r0, [fp] 10c20: e3500000 cmp r0, #0 10c24: 0a000062 beq 10db4 <main.init.1+0x1b4> 10c28: e59f1190 ldr r1, [pc, #400] ; 10dc0 <main.init.1+0x1c0> 10c2c: e28d0004 add r0, sp, #4 10c30: e4912004 ldr r2, [r1], #4 10c34: e4802004 str r2, [r0], #4 10c38: e4912004 ldr r2, [r1], #4 10c3c: e4802004 str r2, [r0], #4 10c40: eb021a3a bl 97530 <os.Getenv> 10c44: e28d000c add r0, sp, #12 10c48: e5901000 ldr r1, [r0] 10c4c: e5901004 ldr r1, [r0, #4] 10c50: e58d1034 str r1, [sp, #52] ; 0x34 10c54: e59d0034 ldr r0, [sp, #52] ; 0x34 10c58: e3500000 cmp r0, #0 10c5c: 0a000054 beq 10db4 <main.init.1+0x1b4> 10c60: e59f115c ldr r1, [pc, #348] ; 10dc4 <main.init.1+0x1c4> 10c64: e28d0004 add r0, sp, #4 10c68: e4912004 ldr r2, [r1], #4 10c6c: e4802004 str r2, [r0], #4 10c70: e4912004 ldr r2, [r1], #4 10c74: e4802004 str r2, [r0], #4 20 ARM
88. 21 THE SECRET OF MONKEY ISLAND
89. 22
90. 22 1. Fetch instruction
91. 22 1. Fetch instruction 2. Execute instruction
92. 22 1. Fetch instruction 2. Execute instruction 3. Move to next instruction
93. 23 RPC Program counter
94. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 24 RPC 0
95. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 24 RPC 6
96. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 24 RPC 12
97. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 24 RPC 18
98. 1000 000c 7f38 1001 0003 e0d3 1201 0000 0000 0720 0f02 01 1301 0001 0f00 02 060c 0e00 ff 24 RPC 20
99. 25 General-purpose registers R0 - R7
100. 26 RFLAGS Flags register (equal, greater than)
101. 27 j je jne jg jge jl jle cmp mod add sub mul div xor or and shl shr not lw lh lb sw sh sb STACK FUNC SPECIAL call ret push pop prn halt BRANCHING ARITHMETIC mov li MEMORY REG
102. DEMO 28
103. github.com/ddfreyne/rcpu 29
104. 30 @ddfreyne denis@stoneship.org Denis Defreyne Ask me about Belgian beer.
105. 31 This talk would not have been the same without some great assets that I could use for free. The fonts in this presentation are Clear Sans by Intel (01.org/clear-sans) and Ubuntu Mono by Canonical Ltd (font.ubuntu.com). The apple sprite is by http://chrisdesign.wordpress.com/.
106. Extra slides 32
107. 33
108. 33 25 15
109. 33 25 15 RPC + 5
110. 33 25 15 RPC + 5 CALLER
111. 33 25 15 RPC + 5 CALLER CALLEE
112. 33 25 15 RPC + 5 old RBP CALLER CALLEE
113. 33 25 15 RPC + 5 old RBP old R0 old R1 old R2 CALLER CALLEE
114. 33 25 15 RPC + 5 old RBP CALLER CALLEE
115. 33 25 15 RPC + 5 CALLER CALLEE
116. 33 25 15 CALLER CALLEE
117. 33 CALLER CALLEE
118. 34
119. lv r0, 100 34
120. lv r0, 100 cmpi r0, 100 # rflags is now 0x01 (equal) 34
121. lv r0, 100 cmpi r0, 100 # rflags is now 0x01 (equal) cmpi r0, 99 # rflags is now 0x02 (greater than) 34
122. 35 RIVEN
123. 36 RIVEN
124. 37 Z-CODE
125. 38 MARGARET HAMILTON