1 /* The IGEN simulator generator for GDB, the GNU Debugger.
3 Copyright 2002 Free Software Foundation, Inc.
5 Contributed by Andrew Cagney.
7 This file is part of GDB.
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.
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.
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. */
25 /* Instruction decode table:
33 ":" [ <constant-field-names> ]
35 ":" [ <format-names> ]
38 ":" [ <path> { "," <path> } ]
40 ":" [ "!" ] <special-value>
46 <path> ::= <int> "," <int> ;;
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"
66 The instruction decode table contains rules that dictate how igen
67 is going to firstly break down the opcode table and secondly
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.
74 In parallel to this, as mentioned above, WITH_EXPANDED_SEMANTICS
75 determines of the semantic functions themselves should be expanded
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.
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.
97 Treat `/' (reserved) fields as a constant (zero) instead of
98 variable when looking for an instruction field.
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.
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).
118 Special rule to fine tune how specific (or groups) of instructions
119 are expanded. The applicability of the rule is determined by
121 <special_mask> != 0 && (instruction> & <special_mask>) == <special_value>
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:
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
139 } decode_special_type
;
152 decode_cond_mask_field
,
153 decode_cond_value_field
,
154 decode_cond_word_nr_field
,
155 nr_decode_cond_fields
,
158 typedef struct _decode_path decode_path
;
159 struct _decode_path
{
164 typedef struct _decode_path_list decode_path_list
;
165 struct _decode_path_list
{
167 decode_path_list
*next
;
171 typedef struct _decode_cond decode_cond
;
172 struct _decode_cond
{
174 int mask
[max_insn_bit_size
];
175 int value
[max_insn_bit_size
];
182 decode_find_constants
,
184 } decode_search_type
;
187 decode_options_field
,
190 decode_force_first_field
,
191 decode_force_last_field
,
192 decode_constant_field_names_field
,
193 decode_word_nr_field
,
194 decode_format_names_field
,
195 decode_model_names_field
,
198 min_nr_decode_fields
= decode_last_field
+ 1,
202 typedef struct _decode_table decode_table
;
203 struct _decode_table
{
205 decode_special_type type
;
207 decode_search_type search
;
212 filter
*constant_field_names
;
217 int with_zero_reserved
;
220 /* conditions on the rule being applied */
221 decode_path_list
*paths
;
222 filter
*format_names
;
224 decode_cond
*conditions
;
229 extern decode_table
*load_decode_table
232 extern int decode_table_max_word_nr
233 (decode_table
*rule
);
235 extern void dump_decode_rule