Added tool bison++-1.21.11

1 files changed, 593 insertions, 0 deletions

diff --git a/tools/bison++/reduce.cc b/tools/bison++/reduce.cc
new file mode 100644
index 000000000..7b0954af1
--- /dev/null
+++ b/tools/bison++/reduce.cc
@@ -0,0 +1,593 @@
+/* Grammar reduction for Bison.
+   Copyright (C) 1988, 1989 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, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+
+/*
+ * Reduce the grammar:  Find and eliminate unreachable terminals,
+ * nonterminals, and productions.  David S. Bakin.
+ */
+
+/*
+ * Don't eliminate unreachable terminals:  They may be used by the user's
+ * parser.
+ */
+
+#include <stdio.h>
+#include "system.h"
+#include "files.h"
+#include "gram.h"
+#include "machine.h"
+#include "new.h"
+
+
+extern char   **tags;		/* reader.c */
+extern int      verboseflag;	/* getargs.c */
+static int      statisticsflag;	/* XXXXXXX */
+
+#ifndef TRUE
+#define TRUE	(1)
+#define FALSE	(0)
+#endif
+
+typedef unsigned *BSet;
+typedef short  *rule;
+
+
+/*
+ * N is set of all nonterminals which are not useless.  P is set of all rules
+ * which have no useless nonterminals in their RHS.  V is the set of all
+ * accessible symbols.
+ */
+
+static BSet     N, P, V, V1;
+
+static int      nuseful_productions, nuseless_productions,
+                nuseful_nonterminals, nuseless_nonterminals;
+
+
+static void useless_nonterminals();
+static void inaccessable_symbols();
+static void reduce_grammar_tables();
+static void print_results();
+static void print_notices();
+void dump_grammar();
+
+extern void fatals(const char*,void*);
+extern void fatals(const char*,void*,void*);
+extern void fatals(const char*,void*,void*,void*);
+extern void fatals(const char*,void*,void*,void*,void*);
+extern void fatals(const char*,void*,void*,void*,void*,void*);
+
+bool
+bits_equal (BSet L, BSet R, int n)
+{
+  int i;
+
+  for (i = n - 1; i >= 0; i--)
+    if (L[i] != R[i])
+      return FALSE;
+  return TRUE;
+}
+
+
+int
+nbits (unsigned i)
+{
+  int count = 0;
+
+  while (i != 0) {
+    i ^= (i & -i);
+    ++count;
+  }
+  return count;
+}
+
+
+int
+bits_size (BSet S, int n)
+{
+  int i, count = 0;
+
+  for (i = n - 1; i >= 0; i--)
+    count += nbits(S[i]);
+  return count;
+}
+
+void
+reduce_grammar ()
+{
+  bool reduced;
+
+  /* Allocate the global sets used to compute the reduced grammar */
+
+  N = NEW2(WORDSIZE(nvars), unsigned);
+  P = NEW2(WORDSIZE(nrules + 1), unsigned);
+  V = NEW2(WORDSIZE(nsyms), unsigned);
+  V1 = NEW2(WORDSIZE(nsyms), unsigned);
+
+  useless_nonterminals();
+  inaccessable_symbols();
+
+  reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0);
+
+  if (verboseflag)
+    print_results();
+
+  if (reduced == FALSE)
+    goto done_reducing;
+
+  print_notices();
+
+  if (!BITISSET(N, start_symbol - ntokens))
+    fatals("Start symbol %s does not derive any sentence.",
+	   tags[start_symbol]);
+
+  reduce_grammar_tables();
+  /* if (verboseflag) {
+     fprintf(foutput, "REDUCED GRAMMAR\n\n");
+     dump_grammar();
+     }
+     */
+
+  /**/ statisticsflag = FALSE; /* someday getopts should handle this */
+  if (statisticsflag == TRUE)
+    fprintf(stderr,
+	    "reduced %s defines %d terminal%s, %d nonterminal%s\
+, and %d production%s.\n", infile,
+	    ntokens, (ntokens == 1 ? "" : "s"),
+	    nvars,   (nvars   == 1 ? "" : "s"),
+	    nrules,  (nrules  == 1 ? "" : "s"));
+
+ done_reducing:
+
+  /* Free the global sets used to compute the reduced grammar */
+
+  FREE(N);
+  FREE(V);
+  FREE(P);
+
+}
+
+/*
+ * Another way to do this would be with a set for each production and then do
+ * subset tests against N, but even for the C grammar the whole reducing
+ * process takes only 2 seconds on my 8Mhz AT.
+ */
+
+static bool 
+useful_production (int i, BSet N)
+{
+  rule  r;
+  short n;
+
+  /*
+   * A production is useful if all of the nonterminals in its RHS
+   * appear in the set of useful nonterminals.
+   */
+
+  for (r = &ritem[rrhs[i]]; *r > 0; r++)
+    if (ISVAR(n = *r))
+      if (!BITISSET(N, n - ntokens))
+	return FALSE;
+  return TRUE;
+}
+
+
+/* Remember that rules are 1-origin, symbols are 0-origin. */
+
+static void 
+useless_nonterminals ()
+{
+  BSet Np, Ns;
+  int  i, n;
+
+  /*
+   * N is set as built.  Np is set being built this iteration. P is set
+   * of all productions which have a RHS all in N.
+   */
+
+  Np = NEW2(WORDSIZE(nvars), unsigned);
+
+  /*
+   * The set being computed is a set of nonterminals which can derive
+   * the empty string or strings consisting of all terminals. At each
+   * iteration a nonterminal is added to the set if there is a
+   * production with that nonterminal as its LHS for which all the
+   * nonterminals in its RHS are already in the set.  Iterate until the
+   * set being computed remains unchanged.  Any nonterminals not in the
+   * set at that point are useless in that they will never be used in
+   * deriving a sentence of the language.
+   * 
+   * This iteration doesn't use any special traversal over the
+   * productions.  A set is kept of all productions for which all the
+   * nonterminals in the RHS are in useful.  Only productions not in
+   * this set are scanned on each iteration.  At the end, this set is
+   * saved to be used when finding useful productions: only productions
+   * in this set will appear in the final grammar.
+   */
+
+  n = 0;
+  while (1)
+    {
+      for (i = WORDSIZE(nvars) - 1; i >= 0; i--)
+	Np[i] = N[i];
+      for (i = 1; i <= nrules; i++)
+	{
+	  if (!BITISSET(P, i))
+	    {
+	      if (useful_production(i, N))
+		{
+		  SETBIT(Np, rlhs[i] - ntokens);
+		  SETBIT(P, i);
+		}
+	    }
+	}
+      if (bits_equal(N, Np, WORDSIZE(nvars)))
+	break;
+      Ns = Np;
+      Np = N;
+      N = Ns;
+    }
+  FREE(N);
+  N = Np;
+}
+
+static void 
+inaccessable_symbols ()
+{
+  BSet  Vp, Vs, Pp;
+  int   i, n;
+  short t;
+  rule  r;
+
+  /*
+   * Find out which productions are reachable and which symbols are
+   * used.  Starting with an empty set of productions and a set of
+   * symbols which only has the start symbol in it, iterate over all
+   * productions until the set of productions remains unchanged for an
+   * iteration.  For each production which has a LHS in the set of
+   * reachable symbols, add the production to the set of reachable
+   * productions, and add all of the nonterminals in the RHS of the
+   * production to the set of reachable symbols.
+   * 
+   * Consider only the (partially) reduced grammar which has only
+   * nonterminals in N and productions in P.
+   * 
+   * The result is the set P of productions in the reduced grammar, and
+   * the set V of symbols in the reduced grammar.
+   * 
+   * Although this algorithm also computes the set of terminals which are
+   * reachable, no terminal will be deleted from the grammar. Some
+   * terminals might not be in the grammar but might be generated by
+   * semantic routines, and so the user might want them available with
+   * specified numbers.  (Is this true?)  However, the nonreachable
+   * terminals are printed (if running in verbose mode) so that the user
+   * can know.
+   */
+
+  Vp = NEW2(WORDSIZE(nsyms), unsigned);
+  Pp = NEW2(WORDSIZE(nrules + 1), unsigned);
+
+  /* If the start symbol isn't useful, then nothing will be useful. */
+  if (!BITISSET(N, start_symbol - ntokens))
+    goto end_iteration;
+
+  SETBIT(V, start_symbol);
+
+  n = 0;
+  while (1)
+    {
+      for (i = WORDSIZE(nsyms) - 1; i >= 0; i--)
+	Vp[i] = V[i];
+      for (i = 1; i <= nrules; i++)
+	{
+	  if (!BITISSET(Pp, i) && BITISSET(P, i) && 
+	      BITISSET(V, rlhs[i]))
+	    {
+	      for (r = &ritem[rrhs[i]]; *r >= 0; r++)
+		{
+		  if (ISTOKEN(t = *r)
+		      || BITISSET(N, t - ntokens))
+		    {
+		      SETBIT(Vp, t);
+		    }
+		}
+	      SETBIT(Pp, i);
+	    }
+	}
+      if (bits_equal(V, Vp, WORDSIZE(nsyms)))
+	{
+	  break;
+	}
+      Vs = Vp;
+      Vp = V;
+      V = Vs;
+    }
+ end_iteration:
+
+  FREE(V);
+  V = Vp;
+
+  /* Tokens 0, 1, and 2 are internal to Bison.  Consider them useful. */
+  SETBIT(V, 0);			/* end-of-input token */
+  SETBIT(V, 1);			/* error token */
+  SETBIT(V, 2);			/* illegal token */
+
+  FREE(P);
+  P = Pp;
+
+  nuseful_productions = bits_size(P, WORDSIZE(nrules + 1));
+  nuseless_productions = nrules - nuseful_productions;
+
+  nuseful_nonterminals = 0;
+  for (i = ntokens; i < nsyms; i++)
+    if (BITISSET(V, i))
+      nuseful_nonterminals++;
+  nuseless_nonterminals = nvars - nuseful_nonterminals;
+
+  /* A token that was used in %prec should not be warned about.  */
+  for (i = 1; i < nrules; i++)
+    if (rprecsym[i] != 0)
+      SETBIT(V1, rprecsym[i]);
+}
+
+static void 
+reduce_grammar_tables ()
+{
+/* This is turned off because we would need to change the numbers
+   in the case statements in the actions file.  */
+#if 0
+  /* remove useless productions */
+  if (nuseless_productions > 0)
+    {
+      short np, pn, ni, pi;
+
+      np = 0;
+      ni = 0;
+      for (pn = 1; pn <= nrules; pn++)
+	{
+	  if (BITISSET(P, pn))
+	    {
+	      np++;
+	      if (pn != np)
+		{
+		  rlhs[np] = rlhs[pn];
+		  rline[np] = rline[pn];
+		  rprec[np] = rprec[pn];
+		  rassoc[np] = rassoc[pn];
+		  rrhs[np] = rrhs[pn];
+		  if (rrhs[np] != ni)
+		    {
+		      pi = rrhs[np];
+		      rrhs[np] = ni;
+		      while (ritem[pi] >= 0)
+			ritem[ni++] = ritem[pi++];
+		      ritem[ni++] = -np;
+		    }
+		} else {
+		  while (ritem[ni++] >= 0);
+		}
+	    }
+	}
+      ritem[ni] = 0;
+      nrules -= nuseless_productions;
+      nitems = ni;
+
+      /*
+       * Is it worth it to reduce the amount of memory for the
+       * grammar? Probably not.
+       */
+
+    }
+#endif /* 0 */
+  /* Disable useless productions,
+     since they may contain useless nonterms
+     that would get mapped below to -1 and confuse everyone.  */
+  if (nuseless_productions > 0)
+    {
+      int pn;
+
+      for (pn = 1; pn <= nrules; pn++)
+	{
+	  if (!BITISSET(P, pn))
+	    {
+	      rlhs[pn] = -1;
+	    }
+	}
+    }
+
+  /* remove useless symbols */
+  if (nuseless_nonterminals > 0)
+    {
+
+      int    i, n;
+/*      short  j; JF unused */
+      short *nontermmap;
+      rule   r;
+
+      /*
+       * create a map of nonterminal number to new nonterminal
+       * number. -1 in the map means it was useless and is being
+       * eliminated.
+       */
+
+      nontermmap = NEW2(nvars, short) - ntokens;
+      for (i = ntokens; i < nsyms; i++)
+	nontermmap[i] = -1;
+
+      n = ntokens;
+      for (i = ntokens; i < nsyms; i++)
+	if (BITISSET(V, i))
+	  nontermmap[i] = n++;
+
+      /* Shuffle elements of tables indexed by symbol number.  */
+
+      for (i = ntokens; i < nsyms; i++)
+	{
+	  n = nontermmap[i];
+	  if (n >= 0)
+	    {
+	      sassoc[n] = sassoc[i];
+	      sprec[n] = sprec[i];
+	      tags[n] = tags[i];
+	    } else {
+	      free(tags[i]);
+	    }
+	}
+
+      /* Replace all symbol numbers in valid data structures.  */
+
+      for (i = 1; i <= nrules; i++)
+	{
+	  /* Ignore the rules disabled above.  */
+	  if (rlhs[i] >= 0)
+	    rlhs[i] = nontermmap[rlhs[i]];
+	  if (ISVAR (rprecsym[i]))
+	    /* Can this happen?  */
+	    rprecsym[i] = nontermmap[rprecsym[i]];
+	}
+
+      for (r = ritem; *r; r++)
+	if (ISVAR(*r))
+	  *r = nontermmap[*r];
+
+      start_symbol = nontermmap[start_symbol];
+
+      nsyms -= nuseless_nonterminals;
+      nvars -= nuseless_nonterminals;
+
+      free(&nontermmap[ntokens]);
+    }
+}
+
+static void 
+print_results ()
+{
+  int   i;
+/*  short j; JF unused */
+  rule  r;
+  bool  b;
+
+  if (nuseless_nonterminals > 0)
+    {
+      fprintf(foutput, "Useless nonterminals:\n\n");
+      for (i = ntokens; i < nsyms; i++)
+	if (!BITISSET(V, i))
+	  fprintf(foutput, "   %s\n", tags[i]);
+    }
+  b = FALSE;
+  for (i = 0; i < ntokens; i++)
+    {
+      if (!BITISSET(V, i) && !BITISSET(V1, i))
+	{
+	  if (!b)
+	    {
+	      fprintf(foutput, "\n\nTerminals which are not used:\n\n");
+	      b = TRUE;
+	    }
+	  fprintf(foutput, "   %s\n", tags[i]);
+	}
+    }
+
+  if (nuseless_productions > 0)
+    {
+      fprintf(foutput, "\n\nUseless rules:\n\n");
+      for (i = 1; i <= nrules; i++)
+	{
+	  if (!BITISSET(P, i))
+	    {
+	      fprintf(foutput, "#%-4d  ", i);
+	      fprintf(foutput, "%s :\t", tags[rlhs[i]]);
+	      for (r = &ritem[rrhs[i]]; *r >= 0; r++)
+		{
+		  fprintf(foutput, " %s", tags[*r]);
+		}
+	      fprintf(foutput, ";\n");
+	    }
+	}
+    }
+  if (nuseless_nonterminals > 0 || nuseless_productions > 0 || b)
+    fprintf(foutput, "\n\n");
+}
+
+void 
+dump_grammar ()
+{
+  int i;
+  rule r;
+
+  fprintf(foutput,
+	  "ntokens = %d, nvars = %d, nsyms = %d, nrules = %d, nitems = %d\n\n",
+	  ntokens, nvars, nsyms, nrules, nitems);
+  fprintf(foutput, "Variables\n---------\n\n");
+  fprintf(foutput, "Value  Sprec    Sassoc    Tag\n");
+  for (i = ntokens; i < nsyms; i++)
+    fprintf(foutput, "%5d  %5d  %5d  %s\n",
+	    i, sprec[i], sassoc[i], tags[i]);
+  fprintf(foutput, "\n\n");
+  fprintf(foutput, "Rules\n-----\n\n");
+  for (i = 1; i <= nrules; i++)
+    {
+      fprintf(foutput, "%-5d(%5d%5d)%5d : (@%-5d)", 
+	      i, rprec[i], rassoc[i], rlhs[i], rrhs[i]);
+      for (r = &ritem[rrhs[i]]; *r > 0; r++)
+	fprintf(foutput, "%5d", *r);
+      fprintf(foutput, " [%d]\n", -(*r));
+    }
+  fprintf(foutput, "\n\n");
+  fprintf(foutput, "Rules interpreted\n-----------------\n\n");
+  for (i = 1; i <= nrules; i++)
+    {
+      fprintf(foutput, "%-5d  %s :", i, tags[rlhs[i]]);
+      for (r = &ritem[rrhs[i]]; *r > 0; r++)
+	fprintf(foutput, " %s", tags[*r]);
+      fprintf(foutput, "\n");
+    }
+  fprintf(foutput, "\n\n");
+}
+
+
+static void 
+print_notices ()
+{
+  extern int fixed_outfiles;
+
+  if (fixed_outfiles && nuseless_productions)
+    fprintf(stderr, "%d rules never reduced\n", nuseless_productions);
+
+  fprintf(stderr, "%s contains ", infile);
+
+  if (nuseless_nonterminals > 0)
+    {
+      fprintf(stderr, "%d useless nonterminal%s",
+	      nuseless_nonterminals,
+	      (nuseless_nonterminals == 1 ? "" : "s"));
+    }
+  if (nuseless_nonterminals > 0 && nuseless_productions > 0)
+    fprintf(stderr, " and ");
+
+  if (nuseless_productions > 0)
+    {
+      fprintf(stderr, "%d useless rule%s",
+	      nuseless_productions,
+	      (nuseless_productions == 1 ? "" : "s"));
+    }
+  fprintf(stderr, ".\n");
+  fflush(stderr);
+}