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236 lines
6.2 KiB
C
236 lines
6.2 KiB
C
/* This file is part of the program psim.
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Copyright (C) 1994,1995,1996, Andrew Cagney <cagney@highland.com.au>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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/* Instruction decode table:
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<decode-rule> ::=
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{ <option> }
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":" [ <first> ]
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":" [ <last> ]
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":" [ <force-first> ]
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":" [ <force-last> ]
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":" [ <constant-field-names> ]
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":" [ <word-nr> ]
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":" [ <format-names> ]
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":" [ <model-names> ]
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":" [ <constant> ]
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":" [ <path> { "," <path> } ]
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{ ":" <special-mask>
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":" [ "!" ] <special-value>
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":" <word-nr> }
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<nl>
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;
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<path> ::= <int> "," <int> ;;
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<option> ::=
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<reserved-options>
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| <code-options>
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| <optimize-options>
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| <decode-options>
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| <constant>
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| <search-options>
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;
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<reserved-options> ::= "zero-reserved" ;
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<gen-options> ::= "array" | "switch" | "padded-switch" | "goto-switch" ;
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<optimize-options> ::= "duplicate" | "combine"
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<decode-options> ::= "normal" | "boolean" ;
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<search-options> ::= "constants" | "variables" | "mixed"
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Ignore the below:
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The instruction decode table contains rules that dictate how igen
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is going to firstly break down the opcode table and secondly
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The table that follows is used by gen to construct a decision tree
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that can identify each possible instruction. Gen then outputs this
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decision tree as (according to config) a table or switch statement
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as the function idecode.
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In parallel to this, as mentioned above, WITH_EXPANDED_SEMANTICS
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determines of the semantic functions themselves should be expanded
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in a similar way.
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<first>
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<last>
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Range of bits (within the instruction) that should be searched for
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an instruction field. Within such ranges, gen looks for opcodes
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(constants), registers (strings) and reserved bits (slash) and
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according to the rules that follows includes or excludes them from
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a possible instruction field.
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<force_first>
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<force_last>
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If an instruction field was found, enlarge the field size so that
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it is forced to at least include bits starting from <force_first>
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(<force_last>). To stop this occuring, use <force_first> = <last>
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+ 1 and <force_last> = <first> - 1.
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<force_reserved>
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Treat `/' (reserved) fields as a constant (zero) instead of
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variable when looking for an instruction field.
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<force_expansion>
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Treat any contained register (string) fields as constant when
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determining the instruction field. For the instruction decode (and
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controled by IDECODE_EXPAND_SEMANTICS) this forces the expansion of
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what would otherwize be non constant bits of an instruction.
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<use_switch>
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Should this table be expanded using a switch statement (val 1) and
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if so, should it be padded with entries so as to force the compiler
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to generate a jump table (val 2). Or a branch table (val 3).
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<special_mask>
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<special_value>
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<special_rule>
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<special_constant>
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Special rule to fine tune how specific (or groups) of instructions
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are expanded. The applicability of the rule is determined by
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<special_mask> != 0 && (instruction> & <special_mask>) == <special_value>
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Where <instruction> is obtained by looking only at constant fields
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with in an instructions spec. When determining an expansion, the
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rule is only considered when a node contains a single instruction.
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<special_rule> can be any of:
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0: for this instruction, expand by earlier rules
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1: expand bits <force_low> .. <force_hi> only
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2: boolean expansion of only zero/non-zero cases
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3: boolean expansion of equality of special constant
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*/
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typedef enum {
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normal_decode_rule,
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boolean_rule,
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} decode_special_type;
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typedef enum {
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invalid_gen,
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array_gen,
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switch_gen,
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padded_switch_gen,
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goto_switch_gen,
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} decode_gen_type;
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enum {
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decode_cond_mask_field,
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decode_cond_value_field,
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decode_cond_word_nr_field,
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nr_decode_cond_fields,
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};
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typedef struct _decode_path decode_path;
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struct _decode_path {
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int opcode_nr;
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decode_path *parent;
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};
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typedef struct _decode_path_list decode_path_list;
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struct _decode_path_list {
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decode_path *path;
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decode_path_list *next;
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};
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typedef struct _decode_cond decode_cond;
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struct _decode_cond {
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int word_nr;
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int mask[max_insn_bit_size];
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int value[max_insn_bit_size];
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int is_equal;
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decode_cond *next;
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};
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typedef enum {
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decode_find_mixed,
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decode_find_constants,
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decode_find_strings,
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} decode_search_type;
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enum {
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decode_options_field,
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decode_first_field,
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decode_last_field,
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decode_force_first_field,
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decode_force_last_field,
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decode_constant_field_names_field,
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decode_word_nr_field,
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decode_format_names_field,
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decode_model_names_field,
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decode_paths_field,
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nr_decode_fields,
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min_nr_decode_fields = decode_last_field + 1,
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};
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typedef struct _decode_table decode_table;
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struct _decode_table {
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line_ref *line;
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decode_special_type type;
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decode_gen_type gen;
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decode_search_type search;
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int first;
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int last;
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int force_first;
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int force_last;
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filter *constant_field_names;
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int word_nr;
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/* if a boolean */
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unsigned constant;
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/* options */
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int with_zero_reserved;
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int with_duplicates;
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int with_combine;
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/* conditions on the rule being applied */
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decode_path_list *paths;
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filter *format_names;
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filter *model_names;
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decode_cond *conditions;
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decode_table *next;
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};
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extern decode_table *load_decode_table
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(char *file_name);
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extern int decode_table_max_word_nr
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(decode_table *rule);
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extern void dump_decode_rule
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(lf *file,
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char *prefix,
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decode_table *rule,
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char *suffix);
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