src/lalr.h

   1 /* Compute lookahead criteria for bison,
   2
   3    Copyright (C) 1984, 1986, 1989, 2000, 2002, 2004, 2006-2007,
   4    2009-2015, 2018-2021 Free Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  20
  21 #ifndef LALR_H_
  22 # define LALR_H_
  23
  24 # include <bitset.h>
  25 # include <bitsetv.h>
  26
  27 /* Import the definition of RULE_T. */
  28 # include "gram.h"
  29
  30 /* Import the definition of CORE, TRANSITIONS and REDUCTIONS. */
  31 # include "state.h"
  32
  33
  34 /** Build the LALR(1) automaton.
  35
  36    Find which rules need lookahead in each state, and which lookahead
  37    tokens they accept.
  38
  39    Also builds:
  40      - #goto_map
  41      - #from_state
  42      - #to_state
  43      - #goto_follows
  44 */
  45 void lalr (void);
  46
  47 /**
  48  * Set #nLA and allocate all reduction lookahead sets.  Normally invoked by
  49  * #lalr.
  50  */
  51 void initialize_LA (void);
  52
  53 /**
  54  * Build only:
  55  *   - #goto_map
  56  *   - #from_state
  57  *   - #to_state
  58  * Normally invoked by #lalr.
  59  */
  60 void set_goto_map (void);
  61
  62 /**
  63  * Update state numbers recorded in #goto_map, #from_state, and #to_state such
  64  * that:
  65  *   - \c nstates_old is the old number of states.
  66  *   - Where \c i is the old state number, <tt>old_to_new[i]</tt> is either:
  67  *     - \c nstates_old if state \c i is removed because it is unreachable.
  68  *       Thus, remove all goto entries involving this state.
  69  *     - The new state number.
  70  */
  71 void lalr_update_state_numbers (state_number old_to_new[],
  72                                 state_number nstates_old);
  73
  74
  75 /** Release the information related to lookahead tokens.
  76
  77    Can be performed once the action tables are computed.  */
  78 void lalr_free (void);
  79
  80 typedef size_t goto_number;
  81 # define GOTO_NUMBER_MAXIMUM ((goto_number) -1)
  82
  83 /** Index into #from_state and #to_state.
  84
  85    All the transitions that accept a particular variable are grouped
  86    together in FROM_STATE and TO_STATE, with indexes from GOTO_MAP[I -
  87    NTOKENS] to GOTO_MAP[I - NTOKENS + 1] - 1 (including both).  */
  88 extern goto_number *goto_map;
  89
  90 /** The size of #from_state and #to_state.  */
  91 extern goto_number ngotos;
  92
  93 /** State number which a transition leads from.  */
  94 extern state_number *from_state;
  95
  96 /** State number it leads to.  */
  97 extern state_number *to_state;
  98
  99 /** The number of the goto from state SRC labeled with nterm SYM.  */
 100 goto_number map_goto (state_number src, symbol_number sym);
 101
 102 /* goto_follows[i] is the set of tokens following goto i.  */
 103 extern bitsetv goto_follows;
 104
 105 #endif /* !LALR_H_ */