* src/output.c: Formatting changes.

[bison.git] / src / closure.c

/* Subroutines for bison
   Copyright (C) 1984, 1989, 2000 Free Software Foundation, Inc.

   This file is part of Bison, the GNU Compiler Compiler.

   Bison 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, or (at your option)
   any later version.

   Bison 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 Bison; see the file COPYING.  If not, write to the Free
   Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
   02111-1307, USA.  */


/* Subroutines of file LR0.c.

Entry points:

  closure (items, n)

Given a vector of item numbers items, of length n, set up ruleset and
itemset to indicate what rules could be run and which items could be
accepted when those items are the active ones.

ruleset contains a bit for each rule.  closure sets the bits for all
rules which could potentially describe the next input to be read.

itemset is a vector of item numbers; itemsetend points to just beyond
the end of the part of it that is significant.  closure places there
the indices of all items which represent units of input that could
arrive next.

  initialize_closure (n)

Allocates the itemset and ruleset vectors, and precomputes useful data
so that closure can be called.  n is the number of elements to
allocate for itemset.

  finalize_closure ()

Frees itemset, ruleset and internal data.

*/

#include "system.h"
#include "alloc.h"
#include "gram.h"


extern short **derives;
extern char **tags;

extern void initialize_closure PARAMS((int));
extern void closure PARAMS((short *, int));
extern void finalize_closure PARAMS((void));

static void set_fderives PARAMS((void));
static void set_firsts PARAMS((void));

extern void RTC PARAMS((unsigned *, int));

short *itemset;
short *itemsetend;
static unsigned *ruleset;

/* internal data.  See comments before set_fderives and set_firsts.  */
static unsigned *fderives;
static unsigned *firsts;

/* number of words required to hold a bit for each rule */
static int rulesetsize;

/* number of words required to hold a bit for each variable */
static int varsetsize;

#ifdef DEBUG
static void print_closure PARAMS((int));
static void print_fderives PARAMS((void));
static void print_firsts PARAMS((void));
#endif

void
initialize_closure (int n)
{
  itemset = NEW2(n, short);

  rulesetsize = WORDSIZE(nrules + 1);
  ruleset = NEW2(rulesetsize, unsigned);

  set_fderives();
}



/* set fderives to an nvars by nrules matrix of bits
   indicating which rules can help derive the beginning of the data
   for each nonterminal.  For example, if symbol 5 can be derived as
   the sequence of symbols 8 3 20, and one of the rules for deriving
   symbol 8 is rule 4, then the [5 - ntokens, 4] bit in fderives is set.  */
static void
set_fderives (void)
{
  register unsigned *rrow;
  register unsigned *vrow;
  register int j;
  register unsigned cword;
  register short *rp;
  register int b;

  int ruleno;
  int i;

  fderives = NEW2(nvars * rulesetsize, unsigned) - ntokens * rulesetsize;

  set_firsts();

  rrow = fderives + ntokens * rulesetsize;

  for (i = ntokens; i < nsyms; i++)
    {
      vrow = firsts + ((i - ntokens) * varsetsize);
      cword = *vrow++;
      b = 0;
      for (j = ntokens; j < nsyms; j++)
	{
	  if (cword & (1 << b))
	    {
	      rp = derives[j];
	      while ((ruleno = *rp++) > 0)
		{
		  SETBIT(rrow, ruleno);
		}
	    }

	  b++;
	  if (b >= BITS_PER_WORD && j + 1 < nsyms)
	    {
	      cword = *vrow++;
	      b = 0;
	    }
	}

      rrow += rulesetsize;
    }

#ifdef	DEBUG
  print_fderives();
#endif

  FREE(firsts);
}



/* set firsts to be an nvars by nvars bit matrix indicating which
   items can represent the beginning of the input corresponding to
   which other items.

   For example, if some rule expands symbol 5 into the sequence of
   symbols 8 3 20, the symbol 8 can be the beginning of the data for
   symbol 5, so the bit [8 - ntokens, 5 - ntokens] in firsts is
   set. */

static void
set_firsts (void)
{
  register unsigned *row;
/*   register int done; JF unused */
  register int symbol;
  register short *sp;
  register int rowsize;

  int i;

  varsetsize = rowsize = WORDSIZE(nvars);

  firsts = NEW2(nvars * rowsize, unsigned);

  row = firsts;
  for (i = ntokens; i < nsyms; i++)
    {
      sp = derives[i];
      while (*sp >= 0)
	{
	  symbol = ritem[rrhs[*sp++]];
	  if (ISVAR(symbol))
	    {
	      symbol -= ntokens;
	      SETBIT(row, symbol);
	    }
	}

      row += rowsize;
    }

  RTC(firsts, nvars);

#ifdef	DEBUG
  print_firsts ();
#endif
}


void
closure (short *core, int n)
{
  register int ruleno;
  register unsigned word;
  register short *csp;
  register unsigned *dsp;
  register unsigned *rsp;

  short *csend;
  unsigned *rsend;
  int symbol;
  int itemno;

  rsp = ruleset;
  rsend = ruleset + rulesetsize;
  csend = core + n;

  if (n == 0)
    {
      dsp = fderives + start_symbol * rulesetsize;
      while (rsp < rsend)
	*rsp++ = *dsp++;
    }
  else
    {
      while (rsp < rsend)
	*rsp++ = 0;

      csp = core;
      while (csp < csend)
	{
	  symbol = ritem[*csp++];
	  if (ISVAR(symbol))
	    {
	      dsp = fderives + symbol * rulesetsize;
	      rsp = ruleset;
	      while (rsp < rsend)
		*rsp++ |= *dsp++;
	    }
	}
    }

  ruleno = 0;
  itemsetend = itemset;
  csp = core;
  rsp = ruleset;
  while (rsp < rsend)
    {
      word = *rsp++;
      if (word == 0)
	{
	  ruleno += BITS_PER_WORD;
	}
      else
	{
	  register int b;

	  for (b = 0; b < BITS_PER_WORD; b++)
	    {
	      if (word & (1 << b))
		{
		  itemno = rrhs[ruleno];
		  while (csp < csend && *csp < itemno)
		    *itemsetend++ = *csp++;
		  *itemsetend++ = itemno;
		}

	      ruleno++;
	    }
	}
    }

  while (csp < csend)
    *itemsetend++ = *csp++;

#ifdef	DEBUG
  print_closure(n);
#endif
}


void
finalize_closure (void)
{
  FREE(itemset);
  FREE(ruleset);
  FREE(fderives + ntokens * rulesetsize);
}



#ifdef	DEBUG

static void
print_closure(int n)
{
  register short *isp;

  printf ("\n\nn = %d\n\n", n);
  for (isp = itemset; isp < itemsetend; isp++)
    printf ("   %d\n", *isp);
}


static void
print_firsts (void)
{
  register int i;
  register int j;
  register unsigned *rowp;

  printf ("\n\n\nFIRSTS\n\n");

  for (i = ntokens; i < nsyms; i++)
    {
      printf ("\n\n%s firsts\n\n", tags[i]);

      rowp = firsts + ((i - ntokens) * varsetsize);

      for (j = 0; j < nvars; j++)
	if (BITISSET (rowp, j))
	  printf ("   %s\n", tags[j + ntokens]);
    }
}


static void
print_fderives (void)
{
  register int i;
  register int j;
  register unsigned *rp;

  printf ("\n\n\nFDERIVES\n");

  for (i = ntokens; i < nsyms; i++)
    {
      printf ("\n\n%s derives\n\n", tags[i]);
      rp = fderives + i * rulesetsize;

      for (j = 0; j <= nrules; j++)
	if (BITISSET (rp, j))
	  printf ("   %d\n", j);
    }

  fflush(stdout);
}

#endif