X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/760b53a84bfc0c79bac266414136936400769e33..32e1e0a4865d64946a5497aff057d7be28c1cc3d:/src/reduce.c

diff --git a/src/reduce.c b/src/reduce.c
index 7e164c50..35aab2e7 100644
--- a/src/reduce.c
+++ b/src/reduce.c
@@ -1,5 +1,5 @@
 /* Grammar reduction for Bison.
-   Copyright 1988, 1989, 2000, 2001  Free Software Foundation, Inc.
+   Copyright (C) 1988, 1989, 2000, 2001, 2002  Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
@@ -26,71 +26,34 @@
    user's parser.  */
 
 #include "system.h"
+#include "quotearg.h"
 #include "getargs.h"
 #include "files.h"
+#include "symtab.h"
 #include "gram.h"
 #include "complain.h"
 #include "reduce.h"
 #include "reader.h"
 #include "getargs.h"
-
-typedef unsigned *BSet;
-typedef short *rule;
-
+#include "bitset.h"
 
 /* Set of all nonterminals which are not useless.  */
-static BSet N;
+static bitset N;
 
 /* Set of all rules which have no useless nonterminals in their RHS.  */
-static BSet P;
+static bitset P;
 
 /* Set of all accessible symbols.  */
-static BSet V;
+static bitset V;
 
 /* Set of symbols used to define rule precedence (so they are
    `useless', but no warning should be issued).  */
-static BSet V1;
+static bitset V1;
 
 static int nuseful_productions;
-static int nuseless_productions;
+int nuseless_productions;
 static int nuseful_nonterminals;
-static int nuseless_nonterminals;
-
-static 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;
-}
-
-
-static int
-nbits (unsigned i)
-{
-  int count = 0;
-
-  while (i != 0)
-    {
-      i ^= (i & ((unsigned) (-(int) i)));
-      ++count;
-    }
-  return count;
-}
-
-
-static int
-bits_size (BSet S, int n)
-{
-  int i, count = 0;
-
-  for (i = n - 1; i >= 0; i--)
-    count += nbits (S[i]);
-  return count;
-}
+int nuseless_nonterminals;
 
 /*-------------------------------------------------------------------.
 | Another way to do this would be with a set for each production and |
@@ -99,18 +62,17 @@ bits_size (BSet S, int n)
 `-------------------------------------------------------------------*/
 
 static bool
-useful_production (int i, BSet N0)
+useful_production (int i, bitset N0)
 {
-  rule r;
+  item_number_t *r;
   short n;
 
   /* A production is useful if all of the nonterminals in its appear
      in the set of useful nonterminals.  */
 
-  for (r = &ritem[rule_table[i].rhs]; *r > 0; r++)
-    if (ISVAR (n = *r))
-      if (!BITISSET (N0, n - ntokens))
-	return FALSE;
+  for (r = rules[i].rhs; *r >= 0; r++)
+    if (ISVAR (n = *r) && !bitset_test (N0, n - ntokens))
+      return FALSE;
   return TRUE;
 }
 
@@ -122,13 +84,14 @@ useful_production (int i, BSet N0)
 static void
 useless_nonterminals (void)
 {
-  BSet Np, Ns;
+  bitset Np, Ns;
   int i;
 
   /* 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 = XCALLOC (unsigned, WORDSIZE (nvars));
+  Np = bitset_create (nvars, BITSET_FIXED);
+
 
   /* The set being computed is a set of nonterminals which can derive
      the empty string or strings consisting of all terminals. At each
@@ -148,26 +111,21 @@ useless_nonterminals (void)
 
   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, rule_table[i].lhs - ntokens);
-		  SETBIT (P, i);
-		}
-	    }
-	}
-      if (bits_equal (N, Np, WORDSIZE (nvars)))
+      bitset_copy (Np, N);
+      for (i = 1; i < nrules + 1; i++)
+	if (!bitset_test (P, i)
+	    && useful_production (i, N))
+	  {
+	    bitset_set (Np, rules[i].lhs->number - ntokens);
+	    bitset_set (P, i);
+	  }
+      if (bitset_equal_p (N, Np))
 	break;
       Ns = Np;
       Np = N;
       N = Ns;
     }
-  XFREE (N);
+  bitset_free (N);
   N = Np;
 }
 
@@ -175,10 +133,10 @@ useless_nonterminals (void)
 static void
 inaccessable_symbols (void)
 {
-  BSet Vp, Vs, Pp;
+  bitset Vp, Vs, Pp;
   int i;
   short t;
-  rule r;
+  item_number_t *r;
 
   /* Find out which productions are reachable and which symbols are
      used.  Starting with an empty set of productions and a set of
@@ -203,31 +161,30 @@ inaccessable_symbols (void)
      terminals are printed (if running in verbose mode) so that the
      user can know.  */
 
-  Vp = XCALLOC (unsigned, WORDSIZE (nsyms));
-  Pp = XCALLOC (unsigned, WORDSIZE (nrules + 1));
+  Vp = bitset_create (nsyms, BITSET_FIXED);
+  Pp = bitset_create (nrules + 1, BITSET_FIXED);
 
   /* If the start symbol isn't useful, then nothing will be useful. */
-  if (BITISSET (N, start_symbol - ntokens))
+  if (bitset_test (N, axiom->number - ntokens))
     {
-      SETBIT (V, start_symbol);
+      bitset_set (V, axiom->number);
 
       while (1)
 	{
-	  for (i = WORDSIZE (nsyms) - 1; i >= 0; i--)
-	    Vp[i] = V[i];
-	  for (i = 1; i <= nrules; i++)
+	  bitset_copy (Vp, V);
+	  for (i = 1; i < nrules + 1; i++)
 	    {
-	      if (!BITISSET (Pp, i)
-		  && BITISSET (P, i)
-		  && BITISSET (V, rule_table[i].lhs))
+	      if (!bitset_test (Pp, i)
+		  && bitset_test (P, i)
+		  && bitset_test (V, rules[i].lhs->number))
 		{
-		  for (r = &ritem[rule_table[i].rhs]; *r >= 0; r++)
-		    if (ISTOKEN (t = *r) || BITISSET (N, t - ntokens))
-		      SETBIT (Vp, t);
-		  SETBIT (Pp, i);
+		  for (r = rules[i].rhs; *r >= 0; r++)
+		    if (ISTOKEN (t = *r) || bitset_test (N, t - ntokens))
+		      bitset_set (Vp, t);
+		  bitset_set (Pp, i);
 		}
 	    }
-	  if (bits_equal (V, Vp, WORDSIZE (nsyms)))
+	  if (bitset_equal_p (V, Vp))
 	    break;
 	  Vs = Vp;
 	  Vp = V;
@@ -235,96 +192,90 @@ inaccessable_symbols (void)
 	}
     }
 
-  XFREE (V);
+  bitset_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);		/* some undefined token */
+  bitset_set (V, eoftoken->number);		/* end-of-input token */
+  bitset_set (V, errtoken->number);		/* error token */
+  bitset_set (V, undeftoken->number);		/* some undefined token */
 
-  XFREE (P);
+  bitset_free (P);
   P = Pp;
 
-  nuseful_productions = bits_size (P, WORDSIZE (nrules + 1));
+  nuseful_productions = bitset_count (P);
   nuseless_productions = nrules - nuseful_productions;
 
   nuseful_nonterminals = 0;
   for (i = ntokens; i < nsyms; i++)
-    if (BITISSET (V, i))
+    if (bitset_test (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 (rule_table[i].precsym != 0)
-      SETBIT (V1, rule_table[i].precsym);
+  for (i = 1; i < nrules + 1; i++)
+    if (rules[i].precsym != 0)
+      bitset_set (V1, rules[i].precsym->number);
 }
 
+
+/*-------------------------------------------------------------------.
+| Put the useless productions at the end of RULES, and adjust NRULES |
+| accordingly.                                                       |
+`-------------------------------------------------------------------*/
+
 static void
 reduce_grammar_tables (void)
 {
-/* 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)
-		{
-		  rule_table[np].lhs = rule_table[pn].lhs;
-		  rline[np] = rline[pn];
-		  rule_table[np].prec = rule_table[pn].prec;
-		  rule_table[np].assoc = rule_table[pn].assoc;
-		  rule_table[np].rhs = rule_table[pn].rhs;
-		  if (rule_table[np].rhs != ni)
-		    {
-		      pi = rule_table[np].rhs;
-		      rule_table[np].rhs = 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.  */
+  /* Report and flag useless productions.  */
+  {
+    int r;
+    for (r = 1; r < nrules + 1; r++)
+      {
+	rules[r].useful = bitset_test (P, r);
+	if (!rules[r].useful)
+	  {
+	    LOCATION_PRINT (stderr, rules[r].location);
+	    fprintf (stderr, ": %s: %s: ", _("warning"), _("useless rule"));
+	    rule_print (&rules[r], stderr);
+	  }
+      }
+  }
 
-    }
-#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;
+  /* Map the nonterminals to their new index: useful first, useless
+     afterwards.  Kept for later report.  */
+  {
+    int useful = 1;
+    int useless = nrules + 1 - nuseless_productions;
+    rule_t *rules_sorted = XMALLOC (rule_t, nrules + 1) - 1;
+    int i;
+    for (i = 1; i < nrules + 1; ++i)
+      rules_sorted[rules[i].useful ? useful++ : useless++] = rules[i];
+    free (rules + 1);
+    rules = rules_sorted;
+
+    /* Renumber the rules markers in RITEMS.  */
+    for (i = 1; i < nrules + 1; ++i)
+      {
+	item_number_t *rhsp = rules[i].rhs;
+	for (/* Nothing. */; *rhsp >= 0; ++rhsp)
+	  /* Nothing. */;
+	*rhsp = -i;
+	rules[i].number = i;
+      }
+    nrules -= nuseless_productions;
+  }
 
-      for (pn = 1; pn <= nrules; pn++)
-	{
-	  if (!BITISSET (P, pn))
-	    {
-	      rule_table[pn].lhs = -1;
-	    }
-	}
-    }
+  /* Adjust NRITEMS.  */
+  {
+    int r;
+    int length;
+    for (r = nrules + 1; r < nrules + 1 + nuseless_productions; ++r)
+      {
+	length = rule_rhs_length (&rules[r]);
+	nritems -= length + 1;
+      }
+  }
 }
 
 
@@ -335,68 +286,56 @@ reduce_grammar_tables (void)
 static void
 nonterminals_reduce (void)
 {
-  int i, n;
-  rule r;
+  symbol_number_t i, n;
 
-  /* Create a map of nonterminal number to new nonterminal number. -1
-     in the map means it was useless and is being eliminated.  */
+  /* Map the nonterminals to their new index: useful first, useless
+     afterwards.  Kept for later report.  */
 
-  short *nontermmap = XCALLOC (short, nvars) - ntokens;
+  symbol_number_t *nontermmap = XCALLOC (symbol_number_t, nvars) - ntokens;
   n = ntokens;
   for (i = ntokens; i < nsyms; i++)
-    if (BITISSET (V, i))
+    if (bitset_test (V, i))
       nontermmap[i] = n++;
   for (i = ntokens; i < nsyms; i++)
-    if (!BITISSET (V, i))
-      nontermmap[i] = n++;
+    if (!bitset_test (V, i))
+      {
+	nontermmap[i] = n++;
+	LOCATION_PRINT (stderr, symbols[i]->location);
+	fprintf (stderr, ": %s: %s: %s\n",
+		 _("warning"), _("useless nonterminal"),
+		 symbol_tag_get (symbols[i]));
+      }
 
 
   /* Shuffle elements of tables indexed by symbol number.  */
   {
-    short *sassoc_sorted = XMALLOC (short, nvars) - ntokens;
-    short *sprec_sorted  = XMALLOC (short, nvars) - ntokens;
-    char **tags_sorted   = XMALLOC (char *, nvars) - ntokens;
+    symbol_t **symbols_sorted = XMALLOC (symbol_t *, nvars) - ntokens;
 
     for (i = ntokens; i < nsyms; i++)
-      {
-	n = nontermmap[i];
-	sassoc_sorted[n] = sassoc[i];
-	sprec_sorted[n]  = sprec[i];
-	tags_sorted[n]   = tags[i];
-      }
+      symbols[i]->number = nontermmap[i];
+    for (i = ntokens; i < nsyms; i++)
+      symbols_sorted[nontermmap[i]] = symbols[i];
     for (i = ntokens; i < nsyms; i++)
+      symbols[i] = symbols_sorted[i];
+    free (symbols_sorted + ntokens);
+  }
+
+  {
+    int r;
+    for (r = 1; r < nrules + 1; ++r)
       {
-	sassoc[i] = sassoc_sorted[i];
-	sprec[i]  = sprec_sorted[i];
-	tags[i]   = tags_sorted[i];
+	item_number_t *rhsp;
+	for (rhsp = rules[r].rhs; *rhsp >= 0; ++rhsp)
+	  if (ISVAR (*rhsp))
+	    *rhsp =  symbol_number_as_item_number (nontermmap[*rhsp]);
       }
-    free (sassoc_sorted + ntokens);
-    free (sprec_sorted + ntokens);
-    free (tags_sorted + ntokens);
+    axiom->number = nontermmap[axiom->number];
   }
 
-  /* Replace all symbol numbers in valid data structures.  */
-
-  for (i = 1; i <= nrules; i++)
-    {
-      /* Ignore the rules disabled above.  */
-      if (rule_table[i].lhs >= 0)
-	rule_table[i].lhs = nontermmap[rule_table[i].lhs];
-      if (ISVAR (rule_table[i].precsym))
-	/* Can this happen?  */
-	rule_table[i].precsym = nontermmap[rule_table[i].precsym];
-    }
-
-  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]);
+  free (nontermmap + ntokens);
 }
 
 
@@ -407,92 +346,37 @@ nonterminals_reduce (void)
 void
 reduce_output (FILE *out)
 {
-  int i;
-  rule r;
-  bool b;
-
   if (nuseless_nonterminals > 0)
     {
-      fprintf (out, _("Useless nonterminals:"));
-      fprintf (out, "\n\n");
+      int i;
+      fprintf (out, "%s\n\n", _("Useless nonterminals:"));
       for (i = 0; i < nuseless_nonterminals; ++i)
-	fprintf (out, "   %s\n", tags[nsyms + i]);
+	fprintf (out, "   %s\n", symbol_tag_get (symbols[nsyms + i]));
+      fputs ("\n\n", out);
     }
-  b = FALSE;
-  for (i = 0; i < ntokens; i++)
-    {
-      if (!BITISSET (V, i) && !BITISSET (V1, i))
+
+  {
+    bool b = FALSE;
+    int i;
+    for (i = 0; i < ntokens; i++)
+      if (!bitset_test (V, i) && !bitset_test (V1, i))
 	{
 	  if (!b)
-	    {
-	      fprintf (out, "\n\n");
-	      fprintf (out, _("Terminals which are not used:"));
-	      fprintf (out, "\n\n");
-	      b = TRUE;
-	    }
-	  fprintf (out, "   %s\n", tags[i]);
+	    fprintf (out, "%s\n\n", _("Terminals which are not used:"));
+	  b = TRUE;
+	  fprintf (out, "   %s\n", symbol_tag_get (symbols[i]));
 	}
-    }
+    if (b)
+      fputs ("\n\n", out);
+  }
 
   if (nuseless_productions > 0)
-    {
-      fprintf (out, "\n\n");
-      fprintf (out, _("Useless rules:"));
-      fprintf (out, "\n\n");
-      for (i = 1; i <= nrules; i++)
-	if (!BITISSET (P, i))
-	  {
-	    fprintf (out, "#%-4d  ", i);
-	    fprintf (out, "%s :\t", tags[rule_table[i].lhs]);
-	    for (r = &ritem[rule_table[i].rhs]; *r >= 0; r++)
-	      fprintf (out, " %s", tags[*r]);
-	    fprintf (out, ";\n");
-	  }
-    }
-  if (nuseless_nonterminals > 0 || nuseless_productions > 0 || b)
-    fprintf (out, "\n\n");
+    grammar_rules_partial_print (out, _("Useless rules"),
+				 nrules + 1,
+				 nuseless_productions + nrules + 1);
 }
 
-static void
-dump_grammar (FILE *out)
-{
-  int i;
-  rule r;
-
-  fprintf (out, "REDUCED GRAMMAR\n\n");
-  fprintf (out,
-	   "ntokens = %d, nvars = %d, nsyms = %d, nrules = %d, nitems = %d\n\n",
-	   ntokens, nvars, nsyms, nrules, nitems);
-  fprintf (out, "Variables\n---------\n\n");
-  fprintf (out, "Value  Sprec  Sassoc  Tag\n");
-  for (i = ntokens; i < nsyms; i++)
-    fprintf (out, "%5d  %5d   %5d  %s\n", i, sprec[i], sassoc[i], tags[i]);
-  fprintf (out, "\n\n");
-  fprintf (out, "Rules\n-----\n\n");
-  fprintf (out, "Num (Prec, Assoc) Lhs : (@Rhs) Ritems [Num?]\n");
-  for (i = 1; i <= nrules; i++)
-    {
-      fprintf (out, "%-5d(%5d%5d)%5d : (@%-5d)",
-	       i,
-	       rule_table[i].prec,
-	       rule_table[i].assoc,
-	       rule_table[i].lhs,
-	       rule_table[i].rhs);
-      for (r = &ritem[rule_table[i].rhs]; *r > 0; r++)
-	fprintf (out, "%5d", *r);
-      fprintf (out, " [%d]\n", -(*r));
-    }
-  fprintf (out, "\n\n");
-  fprintf (out, "Rules interpreted\n-----------------\n\n");
-  for (i = 1; i <= nrules; i++)
-    {
-      fprintf (out, "%-5d  %s :", i, tags[rule_table[i].lhs]);
-      for (r = &ritem[rule_table[i].rhs]; *r > 0; r++)
-	fprintf (out, " %s", tags[*r]);
-      fputc ('\n', out);
-    }
-  fprintf (out, "\n\n");
-}
+
 
 
 
@@ -509,7 +393,7 @@ reduce_print (void)
 			       nuseless_productions),
 	     nuseless_productions);
 
-  fprintf (stderr, _("%s contains "), infile);
+  fprintf (stderr, "%s: %s: ", infile, _("warning"));
 
   if (nuseless_nonterminals > 0)
     fprintf (stderr, ngettext ("%d useless nonterminal",
@@ -536,32 +420,35 @@ reduce_grammar (void)
 
   /* Allocate the global sets used to compute the reduced grammar */
 
-  N = XCALLOC (unsigned, WORDSIZE (nvars));
-  P = XCALLOC (unsigned, WORDSIZE (nrules + 1));
-  V = XCALLOC (unsigned, WORDSIZE (nsyms));
-  V1 = XCALLOC (unsigned, WORDSIZE (nsyms));
+  N = bitset_create (nvars, BITSET_FIXED);
+  P =  bitset_create (nrules + 1, BITSET_FIXED);
+  V = bitset_create (nsyms, BITSET_FIXED);
+  V1 = bitset_create (nsyms, BITSET_FIXED);
 
   useless_nonterminals ();
   inaccessable_symbols ();
 
   reduced = (bool) (nuseless_nonterminals + nuseless_productions > 0);
-
   if (!reduced)
     return;
 
   reduce_print ();
 
-  if (!BITISSET (N, start_symbol - ntokens))
+  if (!bitset_test (N, axiom->number - ntokens))
     fatal (_("Start symbol %s does not derive any sentence"),
-	   tags[start_symbol]);
+	   symbol_tag_get (symbols[axiom->number]));
 
-  reduce_grammar_tables ();
+  /* First reduce the nonterminals, as they renumber themselves in the
+     whole grammar.  If you change the order, nonterms would be
+     renumbered only in the reduced grammar.  */
   if (nuseless_nonterminals > 0)
     nonterminals_reduce ();
+  if (nuseless_productions > 0)
+    reduce_grammar_tables ();
 
   if (trace_flag)
     {
-      dump_grammar (stderr);
+      grammar_dump (stderr, "Reduced Grammar");
 
       fprintf (stderr, "reduced %s defines %d terminals, %d nonterminals\
 , and %d productions.\n",
@@ -577,8 +464,8 @@ reduce_grammar (void)
 void
 reduce_free (void)
 {
-  XFREE (N);
-  XFREE (V);
-  XFREE (V1);
-  XFREE (P);
+  bitset_free (N);
+  bitset_free (V);
+  bitset_free (V1);
+  bitset_free (P);
 }