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1 /* The IGEN simulator generator for GDB, the GNU Debugger.
2
3 Copyright 2002, 2007 Free Software Foundation, Inc.
4
5 Contributed by Andrew Cagney.
6
7 This file is part of GDB.
8
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
23
24
25 /* Instruction decode table:
26
27 <decode-rule> ::=
28 { <option> }
29 ":" [ <first> ]
30 ":" [ <last> ]
31 ":" [ <force-first> ]
32 ":" [ <force-last> ]
33 ":" [ <constant-field-names> ]
34 ":" [ <word-nr> ]
35 ":" [ <format-names> ]
36 ":" [ <model-names> ]
37 ":" [ <constant> ]
38 ":" [ <path> { "," <path> } ]
39 { ":" <special-mask>
40 ":" [ "!" ] <special-value>
41 ":" <word-nr> }
42 <nl>
43 ;
44
45
46 <path> ::= <int> "," <int> ;;
47
48 <option> ::=
49 <reserved-options>
50 | <code-options>
51 | <optimize-options>
52 | <decode-options>
53 | <constant>
54 | <search-options>
55 ;
56
57 <reserved-options> ::= "zero-reserved" ;
58 <gen-options> ::= "array" | "switch" | "padded-switch" | "goto-switch" ;
59 <optimize-options> ::= "duplicate" | "combine"
60 <decode-options> ::= "normal" | "boolean" ;
61 <search-options> ::= "constants" | "variables" | "mixed"
62
63 Ignore the below:
64
65
66 The instruction decode table contains rules that dictate how igen
67 is going to firstly break down the opcode table and secondly
68
69 The table that follows is used by gen to construct a decision tree
70 that can identify each possible instruction. Gen then outputs this
71 decision tree as (according to config) a table or switch statement
72 as the function idecode.
73
74 In parallel to this, as mentioned above, WITH_EXPANDED_SEMANTICS
75 determines of the semantic functions themselves should be expanded
76 in a similar way.
77
78 <first>
79 <last>
80
81 Range of bits (within the instruction) that should be searched for
82 an instruction field. Within such ranges, gen looks for opcodes
83 (constants), registers (strings) and reserved bits (slash) and
84 according to the rules that follows includes or excludes them from
85 a possible instruction field.
86
87 <force_first>
88 <force_last>
89
90 If an instruction field was found, enlarge the field size so that
91 it is forced to at least include bits starting from <force_first>
92 (<force_last>). To stop this occuring, use <force_first> = <last>
93 + 1 and <force_last> = <first> - 1.
94
95 <force_reserved>
96
97 Treat `/' (reserved) fields as a constant (zero) instead of
98 variable when looking for an instruction field.
99
100 <force_expansion>
101
102 Treat any contained register (string) fields as constant when
103 determining the instruction field. For the instruction decode (and
104 controled by IDECODE_EXPAND_SEMANTICS) this forces the expansion of
105 what would otherwize be non constant bits of an instruction.
106
107 <use_switch>
108
109 Should this table be expanded using a switch statement (val 1) and
110 if so, should it be padded with entries so as to force the compiler
111 to generate a jump table (val 2). Or a branch table (val 3).
112
113 <special_mask>
114 <special_value>
115 <special_rule>
116 <special_constant>
117
118 Special rule to fine tune how specific (or groups) of instructions
119 are expanded. The applicability of the rule is determined by
120
121 <special_mask> != 0 && (instruction> & <special_mask>) == <special_value>
122
123 Where <instruction> is obtained by looking only at constant fields
124 with in an instructions spec. When determining an expansion, the
125 rule is only considered when a node contains a single instruction.
126 <special_rule> can be any of:
127
128 0: for this instruction, expand by earlier rules
129 1: expand bits <force_low> .. <force_hi> only
130 2: boolean expansion of only zero/non-zero cases
131 3: boolean expansion of equality of special constant
132
133 */
134
135
136 typedef enum
137 {
138 normal_decode_rule,
139 boolean_rule,
140 }
141 decode_special_type;
142
143
144 typedef enum
145 {
146 invalid_gen,
147 array_gen,
148 switch_gen,
149 padded_switch_gen,
150 goto_switch_gen,
151 }
152 decode_gen_type;
153
154
155 enum
156 {
157 decode_cond_mask_field,
158 decode_cond_value_field,
159 decode_cond_word_nr_field,
160 nr_decode_cond_fields,
161 };
162
163 typedef struct _decode_path decode_path;
164 struct _decode_path
165 {
166 int opcode_nr;
167 decode_path *parent;
168 };
169
170 typedef struct _decode_path_list decode_path_list;
171 struct _decode_path_list
172 {
173 decode_path *path;
174 decode_path_list *next;
175 };
176
177
178 typedef struct _decode_cond decode_cond;
179 struct _decode_cond
180 {
181 int word_nr;
182 int mask[max_insn_bit_size];
183 int value[max_insn_bit_size];
184 int is_equal;
185 decode_cond *next;
186 };
187
188 typedef enum
189 {
190 decode_find_mixed,
191 decode_find_constants,
192 decode_find_strings,
193 }
194 decode_search_type;
195
196 enum
197 {
198 decode_options_field,
199 decode_first_field,
200 decode_last_field,
201 decode_force_first_field,
202 decode_force_last_field,
203 decode_constant_field_names_field,
204 decode_word_nr_field,
205 decode_format_names_field,
206 decode_model_names_field,
207 decode_paths_field,
208 nr_decode_fields,
209 min_nr_decode_fields = decode_last_field + 1,
210 };
211
212
213 typedef struct _decode_table decode_table;
214 struct _decode_table
215 {
216 line_ref *line;
217 decode_special_type type;
218 decode_gen_type gen;
219 decode_search_type search;
220 int first;
221 int last;
222 int force_first;
223 int force_last;
224 filter *constant_field_names;
225 int word_nr;
226 /* if a boolean */
227 unsigned constant;
228 /* options */
229 int with_zero_reserved;
230 int with_duplicates;
231 int with_combine;
232 /* conditions on the rule being applied */
233 decode_path_list *paths;
234 filter *format_names;
235 filter *model_names;
236 decode_cond *conditions;
237 decode_table *next;
238 };
239
240
241 extern decode_table *load_decode_table (char *file_name);
242
243 extern int decode_table_max_word_nr (decode_table *rule);
244
245 extern void dump_decode_rule
246 (lf *file, char *prefix, decode_table *rule, char *suffix);