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31
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1 /*
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2 insn_tfm.c
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3 Copyright © 2008 William Astle
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4
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5 This file is part of LWASM.
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6
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7 LWASM is free software: you can redistribute it and/or modify it under the
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8 terms of the GNU General Public License as published by the Free Software
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9 Foundation, either version 3 of the License, or (at your option) any later
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10 version.
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11
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12 This program is distributed in the hope that it will be useful, but WITHOUT
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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15 more details.
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16
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17 You should have received a copy of the GNU General Public License along with
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18 this program. If not, see <http://www.gnu.org/licenses/>.
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19 */
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20
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21 /*
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22 for handling inherent mode instructions
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23 */
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24
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25 #define __insn_inh_c_seen__
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26
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27 #include <ctype.h>
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28 #include <string.h>
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29
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30 #include "lwasm.h"
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31 #include "instab.h"
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32
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33 OPFUNC(insn_tfm)
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34 {
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35 static const char *reglist = "DXYUS AB 00EF";
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36 int r0, r1;
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37 char *c;
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38 int tfm = 0;
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39
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40 c = strchr(reglist, toupper(*(*p)++));
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41 if (!c)
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42 {
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43 register_error(as, l, 1, "Unknown operation");
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44 return;
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45 }
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46 r0 = c - reglist;
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47 if (**p == '+')
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48 {
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49 (*p)++;
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50 tfm = 1;
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51 }
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52 else if (**p == '-')
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53 {
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54 (*p)++;
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55 tfm = 2;
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56 }
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57 if (*(*p)++ != ',')
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58 {
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59 register_error(as, l, 1, "Unknown operation");
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60 return;
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61 }
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62 c = strchr(reglist, toupper(*(*p)++));
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63 if (!c)
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64 {
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65 register_error(as, l, 1, "Unknown operation");
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66 return;
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67 }
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68 r1 = c - reglist;
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69
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70 if (**p == '+')
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71 {
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72 (*p)++;
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73 tfm |= 4;
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74 }
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75 else if (**p == '-')
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76 {
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77 (*p)++;
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78 tfm |= 8;
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79 }
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80
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81 if (**p && !isspace(**p))
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82 {
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83 register_error(as, l, 1, "Bad operand");
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84 return;
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85 }
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86
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87 // valid values of tfm here are:
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88 // 1: r0+,r1 (2)
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89 // 4: r0,r1+ (3)
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90 // 5: r0+,r1+ (0)
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91 // 10: r0-,r1- (1)
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92 switch (tfm)
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93 {
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94 case 5: //r0+,r1+
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95 lwasm_emitop(as, l, instab[opnum].ops[0]);
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96 break;
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97 case 10: //r0-,r1-
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98 lwasm_emitop(as, l, instab[opnum].ops[1]);
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99 break;
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100 case 1: // r0+,r1
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101 lwasm_emitop(as, l, instab[opnum].ops[2]);
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102 break;
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103 case 4: // r0,r1+
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104 lwasm_emitop(as, l, instab[opnum].ops[3]);
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105 break;
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106 default:
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107 register_error(as, l, 1, "Unknown operation");
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108 return;
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109 }
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110 lwasm_emit(as, l, (r0 << 4) | r1);
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111 }
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