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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 3 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, see <http://www.gnu.org/licenses/>.
-
- */
- /* Instruction decode table:
- <options>:<first>:<last>:<force-first>:<force-last>:<force-expand>:<special>...
- 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_slash>
- Treat `/' fields as a constant 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,
- expand_forced_rule,
- boolean_rule,
- nr_decode_rules
- } decode_special_type;
- typedef enum {
- invalid_gen,
- array_gen,
- switch_gen,
- padded_switch_gen,
- goto_switch_gen,
- nr_decode_gen_types,
- } decode_gen_type;
- typedef struct _decode_table decode_table;
- struct _decode_table {
- decode_special_type type;
- decode_gen_type gen;
- int first;
- int last;
- int force_first;
- int force_last;
- int force_slash;
- char *force_expansion;
- unsigned special_mask;
- unsigned special_value;
- unsigned special_constant;
- decode_table *next;
- };
- extern void force_decode_gen_type
- (const char *type);
- extern decode_table *load_decode_table
- (const char *file_name,
- int hi_bit_nr);
- extern void dump_decode_rule
- (decode_table *rule,
- int indent);
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