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c906108c SS |
1 | /* This file is part of the program psim. |
2 | ||
3 | Copyright (C) 1994,1995,1996, Andrew Cagney <cagney@highland.com.au> | |
4 | ||
5 | This program is free software; you can redistribute it and/or modify | |
6 | it under the terms of the GNU General Public License as published by | |
7 | the Free Software Foundation; either version 2 of the License, or | |
8 | (at your option) any later version. | |
9 | ||
10 | This program is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | GNU General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU General Public License | |
16 | along with this program; if not, write to the Free Software | |
17 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
18 | ||
19 | */ | |
20 | ||
21 | /* Instruction decode table: | |
22 | ||
23 | <options>:<first>:<last>:<force-first>:<force-last>:<force-expand>:<special>... | |
24 | ||
25 | ||
26 | ||
27 | Ignore the below: | |
28 | ||
29 | ||
30 | The instruction decode table contains rules that dictate how igen | |
31 | is going to firstly break down the opcode table and secondly | |
32 | ||
33 | The table that follows is used by gen to construct a decision tree | |
34 | that can identify each possible instruction. Gen then outputs this | |
35 | decision tree as (according to config) a table or switch statement | |
36 | as the function idecode. | |
37 | ||
38 | In parallel to this, as mentioned above, WITH_EXPANDED_SEMANTICS | |
39 | determines of the semantic functions themselves should be expanded | |
40 | in a similar way. | |
41 | ||
42 | <first> | |
43 | <last> | |
44 | ||
45 | Range of bits (within the instruction) that should be searched for | |
46 | an instruction field. Within such ranges, gen looks for opcodes | |
47 | (constants), registers (strings) and reserved bits (slash) and | |
48 | according to the rules that follows includes or excludes them from | |
49 | a possible instruction field. | |
50 | ||
51 | <force_first> | |
52 | <force_last> | |
53 | ||
54 | If an instruction field was found, enlarge the field size so that | |
55 | it is forced to at least include bits starting from <force_first> | |
56 | (<force_last>). To stop this occuring, use <force_first> = <last> | |
57 | + 1 and <force_last> = <first> - 1. | |
58 | ||
59 | <force_slash> | |
60 | ||
61 | Treat `/' fields as a constant instead of variable when looking for | |
62 | an instruction field. | |
63 | ||
64 | <force_expansion> | |
65 | ||
66 | Treat any contained register (string) fields as constant when | |
67 | determining the instruction field. For the instruction decode (and | |
68 | controled by IDECODE_EXPAND_SEMANTICS) this forces the expansion of | |
69 | what would otherwize be non constant bits of an instruction. | |
70 | ||
71 | <use_switch> | |
72 | ||
73 | Should this table be expanded using a switch statement (val 1) and | |
74 | if so, should it be padded with entries so as to force the compiler | |
75 | to generate a jump table (val 2). Or a branch table (val 3). | |
76 | ||
77 | <special_mask> | |
78 | <special_value> | |
79 | <special_rule> | |
80 | <special_constant> | |
81 | ||
82 | Special rule to fine tune how specific (or groups) of instructions | |
83 | are expanded. The applicability of the rule is determined by | |
84 | ||
85 | <special_mask> != 0 && (instruction> & <special_mask>) == <special_value> | |
86 | ||
87 | Where <instruction> is obtained by looking only at constant fields | |
88 | with in an instructions spec. When determining an expansion, the | |
89 | rule is only considered when a node contains a single instruction. | |
90 | <special_rule> can be any of: | |
91 | ||
92 | 0: for this instruction, expand by earlier rules | |
93 | 1: expand bits <force_low> .. <force_hi> only | |
94 | 2: boolean expansion of only zero/non-zero cases | |
95 | 3: boolean expansion of equality of special constant | |
96 | ||
97 | */ | |
98 | ||
99 | ||
100 | typedef enum { | |
101 | normal_decode_rule, | |
102 | expand_forced_rule, | |
103 | boolean_rule, | |
104 | nr_decode_rules | |
105 | } decode_special_type; | |
106 | ||
107 | typedef enum { | |
108 | invalid_gen, | |
109 | array_gen, | |
110 | switch_gen, | |
111 | padded_switch_gen, | |
112 | goto_switch_gen, | |
113 | nr_decode_gen_types, | |
114 | } decode_gen_type; | |
115 | ||
116 | ||
117 | typedef struct _decode_table decode_table; | |
118 | struct _decode_table { | |
119 | decode_special_type type; | |
120 | decode_gen_type gen; | |
121 | int first; | |
122 | int last; | |
123 | int force_first; | |
124 | int force_last; | |
125 | int force_slash; | |
126 | char *force_expansion; | |
127 | unsigned special_mask; | |
128 | unsigned special_value; | |
129 | unsigned special_constant; | |
130 | decode_table *next; | |
131 | }; | |
132 | ||
133 | ||
134 | extern void force_decode_gen_type | |
135 | (const char *type); | |
136 | ||
137 | extern decode_table *load_decode_table | |
138 | (char *file_name, | |
139 | int hi_bit_nr); | |
140 | ||
141 | extern void dump_decode_rule | |
142 | (decode_table *rule, | |
143 | int indent); |