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 100typedef enum { 101 normal_decode_rule, 102 expand_forced_rule, 103 boolean_rule, 104 nr_decode_rules 105} decode_special_type; 106 107typedef 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 117typedef struct _decode_table decode_table; 118struct _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 134extern void force_decode_gen_type 135(const char *type); 136 137extern decode_table *load_decode_table 138(char *file_name, 139 int hi_bit_nr); 140 141extern void dump_decode_rule 142(decode_table *rule, 143 int indent); 144