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authorStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
committerStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
commitc906108c21474dfb4ed285bcc0ac6fe02cd400cc (patch)
treea0015aa5cedc19ccbab307251353a41722a3ae13 /sim/igen/ld-decode.h
parentcd946cff9ede3f30935803403f06f6ed30cad136 (diff)
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Initial creation of sourceware repositorygdb-4_18-branchpoint
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+/* This file is part of the program psim.
+
+ Copyright (C) 1994,1995,1996, Andrew Cagney <cagney@highland.com.au>
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+ */
+
+/* Instruction decode table:
+
+ <decode-rule> ::=
+ { <option> }
+ ":" [ <first> ]
+ ":" [ <last> ]
+ ":" [ <force-first> ]
+ ":" [ <force-last> ]
+ ":" [ <constant-field-names> ]
+ ":" [ <word-nr> ]
+ ":" [ <format-names> ]
+ ":" [ <model-names> ]
+ ":" [ <constant> ]
+ ":" [ <path> { "," <path> } ]
+ { ":" <special-mask>
+ ":" [ "!" ] <special-value>
+ ":" <word-nr> }
+ <nl>
+ ;
+
+
+ <path> ::= <int> "," <int> ;;
+
+ <option> ::=
+ <reserved-options>
+ | <code-options>
+ | <optimize-options>
+ | <decode-options>
+ | <constant>
+ | <search-options>
+ ;
+
+ <reserved-options> ::= "zero-reserved" ;
+ <gen-options> ::= "array" | "switch" | "padded-switch" | "goto-switch" ;
+ <optimize-options> ::= "duplicate" | "combine"
+ <decode-options> ::= "normal" | "boolean" ;
+ <search-options> ::= "constants" | "variables" | "mixed"
+
+ Ignore the below:
+
+
+ The instruction decode table contains rules that dictate how igen
+ is going to firstly break down the opcode table and secondly
+
+ The table that follows is used by gen to construct a decision tree
+ that can identify each possible instruction. Gen then outputs this
+ decision tree as (according to config) a table or switch statement
+ as the function idecode.
+
+ In parallel to this, as mentioned above, WITH_EXPANDED_SEMANTICS
+ determines of the semantic functions themselves should be expanded
+ in a similar way.
+
+ <first>
+ <last>
+
+ Range of bits (within the instruction) that should be searched for
+ an instruction field. Within such ranges, gen looks for opcodes
+ (constants), registers (strings) and reserved bits (slash) and
+ according to the rules that follows includes or excludes them from
+ a possible instruction field.
+
+ <force_first>
+ <force_last>
+
+ If an instruction field was found, enlarge the field size so that
+ it is forced to at least include bits starting from <force_first>
+ (<force_last>). To stop this occuring, use <force_first> = <last>
+ + 1 and <force_last> = <first> - 1.
+
+ <force_reserved>
+
+ Treat `/' (reserved) fields as a constant (zero) instead of
+ variable when looking for an instruction field.
+
+ <force_expansion>
+
+ Treat any contained register (string) fields as constant when
+ determining the instruction field. For the instruction decode (and
+ controled by IDECODE_EXPAND_SEMANTICS) this forces the expansion of
+ what would otherwize be non constant bits of an instruction.
+
+ <use_switch>
+
+ Should this table be expanded using a switch statement (val 1) and
+ if so, should it be padded with entries so as to force the compiler
+ to generate a jump table (val 2). Or a branch table (val 3).
+
+ <special_mask>
+ <special_value>
+ <special_rule>
+ <special_constant>
+
+ Special rule to fine tune how specific (or groups) of instructions
+ are expanded. The applicability of the rule is determined by
+
+ <special_mask> != 0 && (instruction> & <special_mask>) == <special_value>
+
+ Where <instruction> is obtained by looking only at constant fields
+ with in an instructions spec. When determining an expansion, the
+ rule is only considered when a node contains a single instruction.
+ <special_rule> can be any of:
+
+ 0: for this instruction, expand by earlier rules
+ 1: expand bits <force_low> .. <force_hi> only
+ 2: boolean expansion of only zero/non-zero cases
+ 3: boolean expansion of equality of special constant
+
+ */
+
+
+typedef enum {
+ normal_decode_rule,
+ boolean_rule,
+} decode_special_type;
+
+
+typedef enum {
+ invalid_gen,
+ array_gen,
+ switch_gen,
+ padded_switch_gen,
+ goto_switch_gen,
+} decode_gen_type;
+
+
+enum {
+ decode_cond_mask_field,
+ decode_cond_value_field,
+ decode_cond_word_nr_field,
+ nr_decode_cond_fields,
+};
+
+typedef struct _decode_path decode_path;
+struct _decode_path {
+ int opcode_nr;
+ decode_path *parent;
+};
+
+typedef struct _decode_path_list decode_path_list;
+struct _decode_path_list {
+ decode_path *path;
+ decode_path_list *next;
+};
+
+
+typedef struct _decode_cond decode_cond;
+struct _decode_cond {
+ int word_nr;
+ int mask[max_insn_bit_size];
+ int value[max_insn_bit_size];
+ int is_equal;
+ decode_cond *next;
+};
+
+typedef enum {
+ decode_find_mixed,
+ decode_find_constants,
+ decode_find_strings,
+} decode_search_type;
+
+enum {
+ decode_options_field,
+ decode_first_field,
+ decode_last_field,
+ decode_force_first_field,
+ decode_force_last_field,
+ decode_constant_field_names_field,
+ decode_word_nr_field,
+ decode_format_names_field,
+ decode_model_names_field,
+ decode_paths_field,
+ nr_decode_fields,
+ min_nr_decode_fields = decode_last_field + 1,
+};
+
+
+typedef struct _decode_table decode_table;
+struct _decode_table {
+ line_ref *line;
+ decode_special_type type;
+ decode_gen_type gen;
+ decode_search_type search;
+ int first;
+ int last;
+ int force_first;
+ int force_last;
+ filter *constant_field_names;
+ int word_nr;
+ /* if a boolean */
+ unsigned constant;
+ /* options */
+ int with_zero_reserved;
+ int with_duplicates;
+ int with_combine;
+ /* conditions on the rule being applied */
+ decode_path_list *paths;
+ filter *format_names;
+ filter *model_names;
+ decode_cond *conditions;
+ decode_table *next;
+};
+
+
+extern decode_table *load_decode_table
+(char *file_name);
+
+extern int decode_table_max_word_nr
+(decode_table *rule);
+
+extern void dump_decode_rule
+(lf *file,
+ char *prefix,
+ decode_table *rule,
+ char *suffix);