sim/igen/ld-decode.h

   1 /* The IGEN simulator generator for GDB, the GNU Debugger.
   2
   3    Copyright 2002 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   normal_decode_rule,
 138   boolean_rule,
 139 } decode_special_type;
 140
 141
 142 typedef enum {
 143   invalid_gen,
 144   array_gen,
 145   switch_gen,
 146   padded_switch_gen,
 147   goto_switch_gen,
 148 } decode_gen_type;
 149
 150
 151 enum {
 152   decode_cond_mask_field,
 153   decode_cond_value_field,
 154   decode_cond_word_nr_field,
 155   nr_decode_cond_fields,
 156 };
 157
 158 typedef struct _decode_path decode_path;
 159 struct _decode_path {
 160   int opcode_nr;
 161   decode_path *parent;
 162 };
 163
 164 typedef struct _decode_path_list decode_path_list;
 165 struct _decode_path_list {
 166   decode_path *path;
 167   decode_path_list *next;
 168 };
 169
 170
 171 typedef struct _decode_cond decode_cond;
 172 struct _decode_cond {
 173   int word_nr;
 174   int mask[max_insn_bit_size];
 175   int value[max_insn_bit_size];
 176   int is_equal;
 177   decode_cond *next;
 178 };
 179
 180 typedef enum {
 181   decode_find_mixed,
 182   decode_find_constants,
 183   decode_find_strings,
 184 } decode_search_type;
 185
 186 enum {
 187   decode_options_field,
 188   decode_first_field,
 189   decode_last_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,
 196   decode_paths_field,
 197   nr_decode_fields,
 198   min_nr_decode_fields = decode_last_field + 1,
 199 };
 200
 201
 202 typedef struct _decode_table decode_table;
 203 struct _decode_table {
 204   line_ref *line;
 205   decode_special_type type;
 206   decode_gen_type gen;
 207   decode_search_type search;
 208   int first;
 209   int last;
 210   int force_first;
 211   int force_last;
 212   filter *constant_field_names;
 213   int word_nr;
 214   /* if a boolean */
 215   unsigned constant;
 216   /* options */
 217   int with_zero_reserved;
 218   int with_duplicates;
 219   int with_combine;
 220   /* conditions on the rule being applied */
 221   decode_path_list *paths;
 222   filter *format_names;
 223   filter *model_names;
 224   decode_cond *conditions;
 225   decode_table *next;
 226 };
 227
 228
 229 extern decode_table *load_decode_table
 230 (char *file_name);
 231
 232 extern int decode_table_max_word_nr
 233 (decode_table *rule);
 234
 235 extern void dump_decode_rule
 236 (lf *file,
 237  char *prefix,
 238  decode_table *rule,
 239  char *suffix);