Mercurial > repos > blastem
comparison 68kinst.c @ 0:2432d177e1ac
Initial work on M68K instruction decoding
author | Mike Pavone <pavone@retrodev.com> |
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date | Mon, 29 Oct 2012 01:18:38 -0700 |
parents | |
children | 5df303bf72e6 |
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-1:000000000000 | 0:2432d177e1ac |
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1 #include "68kinst.h" | |
2 | |
3 void m68k_decode_op(uint16_t op, m68k_op_info *dst) | |
4 { | |
5 uint8_t mode = (op >> 3) & 0x7; | |
6 uint8_t reg = op & 0x7; | |
7 dst->addr_mode = mode; | |
8 switch(mode) | |
9 { | |
10 case MODE_REG: | |
11 case MODE_AREG: | |
12 dst->params.regs.pri = reg; | |
13 break; | |
14 case MODE_ | |
15 } | |
16 } | |
17 | |
18 uint16_t * m68K_decode(uint16_t * istream, m68kinst * decoded) | |
19 { | |
20 uint8_t optype = *istream >> 12; | |
21 uint8_t size; | |
22 uint8_t immed; | |
23 switch(optype) | |
24 { | |
25 case BIT_MOVEP_IMMED: | |
26 //TODO: Implement me | |
27 break; | |
28 case MOVE_BYTE: | |
29 case MOVE_LONG: | |
30 case MOVE_WORD: | |
31 decoded->op = M68K_MOVE; | |
32 decoded->extra.size = optype == MOVE_BYTE ? OPSIZE_BYTE : (optype == MOVE_WORD ? OPSIZE_WORD : OPSIZE_LONG); | |
33 m68k_decode_op(*istream, &(decoded->src)); | |
34 m68k_decode_op(((*istream >> 9) & 0x7) | , &(decoded->dst)); | |
35 break; | |
36 case MISC: | |
37 //TODO: Implement me | |
38 break; | |
39 case QUICK_ARITH_LOOP: | |
40 size = (*istream >> 6) & 3; | |
41 if (size == 0x3) { | |
42 //DBcc, TRAPcc or Scc | |
43 decoded->extra.cond = (*istream >> 0x8) & 0xF; | |
44 switch ((*istream >> 3) & 0x7) | |
45 { | |
46 case 1: //DBcc | |
47 decoded->op = M68K_DBCC; | |
48 decoded->dst.addr_mode = MODE_REG; | |
49 decoded->dst.regs.pri = *istream & 0x7; | |
50 break; | |
51 case 7: //TRAPcc | |
52 decoded->op = M68K_TRAPCC; | |
53 decoded->src.addr_mode = MODE_PC_INDIRECT_ABS_IMMED; | |
54 decoded->src.regs.pri = MODE_IMMEDIATE; | |
55 //TODO: Figure out what to do with OPMODE and optional extention words | |
56 break; | |
57 default: //Scc | |
58 decoded->op = M68K_SCC; | |
59 M68k_decode_op(*istream, &(decoded->dst)); | |
60 break; | |
61 } | |
62 } else { | |
63 //ADDQ, SUBQ | |
64 decoded->variant = VAR_QUICK; | |
65 decoded->extra.size = size; | |
66 decoded->src.addr_mode = MODE_PC_INDIRECT_ABS_IMMED; | |
67 decoded->src.regs.pri = MODE_IMMEDIATE; | |
68 immed = (*istream >> 9) & 0x7 | |
69 if (!immed) { | |
70 immed = 8; | |
71 } | |
72 switch (size) | |
73 { | |
74 case OPSIZE_BYTE; | |
75 decoded->src.params.u8 = immed; | |
76 break; | |
77 case OPSIZE_WORD: | |
78 decoded->src.params.u16 = immed; | |
79 break; | |
80 case OPSIZE_LONG: | |
81 decoded->src.params.u38 = immed; | |
82 break; | |
83 } | |
84 if (*istream & 0x10) { | |
85 decoded->op = M68K_SUB; | |
86 } else { | |
87 decoded->op = M68K_ADD; | |
88 } | |
89 } | |
90 break; | |
91 } | |
92 } |