269 lines
9.4 KiB
Plaintext
269 lines
9.4 KiB
Plaintext
This "Dispatcher" function is at the center of a weird scheme involving jump
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buffers inside GetKeyWait.
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The GetKeyWait function (conditionally) starts by a call to setjmp()
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immediately followed by a call to this dispatcher, passing along the return
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value of the long jump, which has 12 values, as we'll see shortly.
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There are two jump buffers in GetKeyWait, and which one is used depends on a
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RAM global that changes value several times along the execution. Hence, the
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*state* of this scheme consists of:
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-> Which buffer is currently selected;
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-> The return value of the long jump.
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I believe that the scheme is best viewed as a finite state machine, where each
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state change triggers a return to the start of GetKeyWait().
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This Dispatcher function implements some of the logic of that state machine.
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It starts with a jump-table-based switch which executes code depending on the
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return value of the long jump. The executed code does things like:
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* Change the currently-selected buffer and return, letting GetKeyWait execute
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* Change the currently-seletced buffer and long jump back, changing the long
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jump return code and forcing an immediate return to the dispatcher
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* Read and write the state of the SHIFT and ALHA modifiers (even though that is
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normally handled by GetKey()?)
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* Invoke *ENOURMOUS* functions that draw to screen, manipulate the MCS, clear
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VRAM, change the Setup parameters, change the on-screen Cursor, print error
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messages, remap F-key codes, ... (basically everything).
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My best intuition so far is that the two jump buffers are for the add-in and
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the main menu, although I'm not sure why there's a need to save state like
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this. I have no intuition yet about the meaning of the 12 states. Though I do
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suspect that the enormous functions I found are related to starting new
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applications, mainly because of %46d which clears the last three eights of the
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RAM, and %846 which clears 1024 bytes of probably-VRAM. Both are called from
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<80089c12> which is called from <8008a42e> which is called from state #2 (and
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does a hell of a lot of MCS-related calls inside its subroutine <80081cea>).
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<80089d8a GetKeyWait_Dispatcher>
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r4: ??? (return value of setjmp/longmp when called from GetKeyWait_Main)
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appears to be some sort of state (one exists per jump buffer)
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# If r4>11, give up and return r4 itself.
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80089d8a: 4f22 sts.l pr, @-r15
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80089d8c: 7ffc add #-4, r15
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80089d8e: e60b mov #11, r6
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80089d90: 2f42 mov.l r4, @r15
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80089d92: 3466 cmp/hi r6, r4
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80089d94: 8f02 bf.s <80089d9c>
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80089d96: 6243 mov r4, r2
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80089d98: a08a bra <80089eb0>
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80089d9a: 0009 nop
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# Otherwise, jump to 88089da6 + offset_table[r0] (table below)
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80089d9c: 4200 shll r2
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80089d9e: c71c mova.l <80089e10>, r0
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80089da0: 002d mov.w @(r0,r2), r0
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80089da2: 0023 braf r0
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80089da4: 0009 nop
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... (data)
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# Offset table
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80089e10: 010a 010a 0082 008a 0092 0104 00ae 0104 00bc 00d0 00e6 00fc
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# State #2:
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# -> Call <8008a42e>()
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80089e28: b301 bsr <8008a42e>
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80089e2a: 0009 nop
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80089e2c: a040 bra <80089eb0>
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80089e2e: 0009 nop
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# State #3:
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# -> Call <8008a4ca>()
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80089e30: b34b bsr <8008a4ca>
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80089e32: 0009 nop
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80089e34: a03c bra <80089eb0>
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80089e36: 0009 nop
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# State #4:
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# -> Call <8008a98a>()
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# -> Call <8008a8bc>()
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# -> Copy 0x8801b6ce to 0x8801b6cd (possibly stopping this long jump frenzy)
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# -> Move to state #5 of setjmp_buffers[1] by performing a long jump
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80089e38: b5a7 bsr <8008a98a>
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80089e3a: 0009 nop
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80089e3c: b53e bsr <8008a8bc>
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80089e3e: 0009 nop
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80089e40: d282 mov.l 0x8801b6ce, r2
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80089e42: e505 mov #5, r5
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80089e44: d682 mov.l 0x8801b6cd, r6
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80089e46: d783 mov.l %ac9 longjmp, r7
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80089e48: d483 mov.l 0x8801b67c, r4
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80089e4a: 6120 mov.b @r2, r1
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80089e4c: 470b jsr @r7
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80089e4e: 2610 mov.b r1, @r6
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80089e50: a02e bra <80089eb0>
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80089e52: 0009 nop
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# State #6:
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# -> Set setjmp_buffer_index = 0
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# -> Call <8008c5b0>()
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80089e54: d681 mov.l 0x8801b6cc, r6
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80089e56: e200 mov #0, r2
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80089e58: d381 mov.l 0x8008c5b0, r3
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80089e5a: 430b jsr @r3
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80089e5c: 2620 mov.b r2, @r6
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80089e5e: a027 bra <80089eb0>
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80089e60: 0009 nop
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# State #8:
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# -> Set setjmp_buffer_index = 0
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# -> Call <8008ac62>()
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# -> Go to state #9 of setjmp_buffers[1]
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80089e62: d67e mov.l 0x8801b6cc, r6
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80089e64: e400 mov #0, r4
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80089e66: b6fc bsr <8008ac62>
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80089e68: 2640 mov.b r4, @r6
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80089e6a: d77a mov.l %ac9 longjmp, r7
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80089e6c: d47a mov.l 0x8801b67c, r4
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80089e6e: 470b jsr @r7
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80089e70: e509 mov #9, r5
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80089e72: a01d bra <80089eb0>
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80089e74: 0009 nop
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# State #9:
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# -> If SHIFT is pressed but not ALPHA: PutKey(0x7536 == KEY_CTRL_SHIFT, 0)
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# -> Set setjmp_buffer_index = 1
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# Note that 0x910 injects codes into a GetKey()-only buffer and notifies
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# GetKeyWait() by adding special matrix code values to its buffer. This
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# injected SHIFT key will only be seen by GetKey() (which is the one to handle
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# the SHIFT/ALPHA feature anyway).
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80089e76: d27b mov.l %91b GetShiftAlphaState, r2
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80089e78: 420b jsr @r2
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80089e7a: 0009 nop
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80089e7c: 8801 cmp/eq #1, r0
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80089e7e: 8b14 bf <80089eaa>
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80089e80: d279 mov.l %910 PutKey, r2
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80089e82: 949c mov.w 0x00007536, r4
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80089e84: 420b jsr @r2
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80089e86: e500 mov #0, r5
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80089e88: a00f bra <80089eaa>
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80089e8a: 0009 nop
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# State #10:
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# -> Set setjmp_buffer_index = 1
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# -> Call <8008b4e2>()
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# -> Go to state #11 of setjmp_buffers[0] (which just resets the index to 0)
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80089e8c: d673 mov.l 0x8801b6cc, r6
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80089e8e: e101 mov #1, r1
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80089e90: d376 mov.l 0x8008b4e2, r3
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80089e92: 430b jsr @r3
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80089e94: 2610 mov.b r1, @r6
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80089e96: d76f mov.l %ac9 longjmp, r7
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80089e98: d475 mov.l 0x8801b62c, r4
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80089e9a: 470b jsr @r7
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80089e9c: e50b mov #11, r5
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80089e9e: a007 bra <80089eb0>
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80089ea0: 0009 nop
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# State #11:
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# -> Set setjmp_buffer_index = 0
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80089ea2: d66e mov.l 0x8801b6cc, r6
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80089ea4: e200 mov #0, r2
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80089ea6: a003 bra <80089eb0>
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80089ea8: 2620 mov.b r2, @r6
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# States #5 and #7
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# -> Set setjmp_buffer_index = 1
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80089eaa: d66c mov.l 0x8801b6cc, r6
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80089eac: e201 mov #1, r2
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80089eae: 2620 mov.b r2, @r6
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# States #0 and #1, and end of function (normal return)
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80089eb0: 60f2 mov.l @r15, r0
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80089eb2: 7f04 add #4, r15
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80089eb4: 4f26 lds.l @r15+, pr
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80089eb6: 000b rts
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80089eb8: 0009 nop
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---
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<8008a42e>
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Stack> pr (x:u32) (1024 bytes)
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# Set setjmp_buffer_index = 0
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# Call <8008a44c>(0x8024cfb4, 85, *r4)
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8008a42e: 4f22 sts.l pr, @-r15
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8008a430: 7ffc add #-4, r15
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8008a432: d76c mov.l 0x8801b6cc, r7
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8008a434: e504 mov #4, r5
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8008a436: d46d mov.l 0x8024cfb4, r4
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8008a438: 62f3 mov r15, r2
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8008a43a: 4518 shll8 r5
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8008a43c: e100 mov #0, r1
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8008a43e: 3258 sub r5, r2
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8008a440: e555 mov #85, r5
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8008a442: 2710 mov.b r1, @r7
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8008a444: a002 bra <8008a44c>
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8008a446: 6642 mov.l @r4, r6
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8008a448: 2250 mov.b r5, @r2
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8008a44a: 72ff add #-1, r2
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8008a44c: 3626 cmp/hi r2, r6
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8008a44e: 8bfb bf <8008a448>
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8008a450: bbdf bsr <80089c12>
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8008a452: 0009 nop
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8008a454: d566 mov.l 0x8801b6d6, r5
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8008a456: d167 mov.l 0x8801b6d2, r1
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8008a458: 6251 mov.w @r5, r2
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8008a45a: 8551 mov.w @(2,r5), r0
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8008a45c: 8111 mov.w r0, @(2,r1)
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8008a45e: 6603 mov r0, r6
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8008a460: 6023 mov r2, r0
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8008a462: 8802 cmp/eq #2, r0
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8008a464: 8f18 bf.s <8008a498>
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8008a466: 2121 mov.w r2, @r1
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8008a468: d463 mov.l 0x8801b6d0, r4
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8008a46a: e201 mov #1, r2
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8008a46c: d363 mov.l 0x8008c1ea, r3
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8008a46e: 430b jsr @r3
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8008a470: 2420 mov.b r2, @r4
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8008a472: 2008 tst r0, r0
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8008a474: 8b08 bf <8008a488>
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8008a476: d15f mov.l 0x8801b6d2, r1
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8008a478: e0ff mov #-1, r0
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8008a47a: d651 mov.l 0x8801b6cd, r6
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8008a47c: 600c extu.b r0, r0
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8008a47e: e203 mov #3, r2
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8008a480: 8111 mov.w r0, @(2,r1)
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8008a482: e008 mov #8, r0
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8008a484: a01d bra <8008a4c2>
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8008a486: 2620 mov.b r2, @r6
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8008a488: d15a mov.l 0x8801b6d2, r1
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8008a48a: e501 mov #1, r5
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8008a48c: e400 mov #0, r4
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8008a48e: 8511 mov.w @(2,r1), r0
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8008a490: b04d bsr <8008a52e>
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8008a492: 6603 mov r0, r6
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8008a494: a015 bra <8008a4c2>
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8008a496: 0009 nop
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8008a498: 0729 movt r7
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8008a49a: d559 mov.l 0x8801b6de, r5
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8008a49c: d156 mov.l 0x8801b6d0, r1
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8008a49e: 6063 mov r6, r0
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8008a4a0: d64e mov.l %aca setjmp, r6
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8008a4a2: d44f mov.l 0x8801b62c, r4
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8008a4a4: 8151 mov.w r0, @(2,r5)
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8008a4a6: 2170 mov.b r7, @r1
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8008a4a8: 460b jsr @r6
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8008a4aa: 2521 mov.w r2, @r5
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8008a4ac: d24d mov.l 0x8801b6cc, r2
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8008a4ae: 6403 mov r0, r4
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8008a4b0: e100 mov #0, r1
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8008a4b2: 2f02 mov.l r0, @r15
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8008a4b4: bc69 bsr <80089d8a>
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8008a4b6: 2210 mov.b r1, @r2
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8008a4b8: d746 mov.l %ac9 longjmp, r7
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8008a4ba: d447 mov.l 0x8801b5dc, r4
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8008a4bc: 470b jsr @r7
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8008a4be: e503 mov #3, r5
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8008a4c0: e006 mov #6, r0
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8008a4c2: 7f04 add #4, r15
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8008a4c4: 4f26 lds.l @r15+, pr
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8008a4c6: 000b rts
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8008a4c8: 0009 nop
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