#
#   This file is part of the program psim.
#
#   Copyright (C) 1994-1995, 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:
#
#   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.
#
#   The table contains the following entries:
#
#   <valid>
#
#   Must be 1 for the entry to be considered.  The last entry must be
#   zero.
#	
#   <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 instructioin 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).
#
#   <special_mask>
#   <special_value>
#   <special_rule>
#
#   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
#
 0: 5: 0: 5:0::              1:0x00000000:0x00000000:0
21:31:32:-1:0::              1:0x00000000:0x00000000:0