X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/c87d4863f6de617e0ed35dc566c59d5b4a072101..74392f6a54a667ced35be695c0ed24b0803e40b6:/src/LR0.c

diff --git a/src/LR0.c b/src/LR0.c
index b67bd78b..d21a946f 100644
--- a/src/LR0.c
+++ b/src/LR0.c
@@ -30,18 +30,17 @@
 #include "complain.h"
 #include "closure.h"
 #include "LR0.h"
-
+#include "lalr.h"
+#include "reduce.h"
 
 int nstates;
 int final_state;
-core *first_state = NULL;
-shifts *first_shift = NULL;
-reductions *first_reduction = NULL;
+static state_t *first_state = NULL;
+static shifts *first_shift = NULL;
 
-static core *this_state = NULL;
-static core *last_state = NULL;
+static state_t *this_state = NULL;
+static state_t *last_state = NULL;
 static shifts *last_shift = NULL;
-static reductions *last_reduction = NULL;
 
 static int nshifts;
 static short *shift_symbol = NULL;
@@ -50,24 +49,26 @@ static short *redset = NULL;
 static short *shiftset = NULL;
 
 static short **kernel_base = NULL;
-static short **kernel_end = NULL;
+static int *kernel_size = NULL;
 static short *kernel_items = NULL;
 
 /* hash table for states, to recognize equivalent ones.  */
 
-#define	STATE_TABLE_SIZE	1009
-static core **state_table = NULL;
+#define	STATE_HASH_SIZE	1009
+static state_t **state_hash = NULL;
 
 
 static void
 allocate_itemsets (void)
 {
   int i;
-  int count;
-  short *symbol_count = NULL;
 
-  count = 0;
-  symbol_count = XCALLOC (short, nsyms);
+  /* Count the number of occurrences of all the symbols in RITEMS.
+     Note that useless productions (hence useless nonterminals) are
+     browsed too, hence we need to allocate room for _all_ the
+     symbols.  */
+  int count = 0;
+  short *symbol_count = XCALLOC (short, nsyms + nuseless_nonterminals);
 
   for (i = 0; ritem[i]; ++i)
     if (ritem[i] > 0)
@@ -93,8 +94,8 @@ allocate_itemsets (void)
       count += symbol_count[i];
     }
 
-  shift_symbol = symbol_count;
-  kernel_end = XCALLOC (short *, nsyms);
+  free (symbol_count);
+  kernel_size = XCALLOC (int, nsyms);
 }
 
 
@@ -105,20 +106,20 @@ allocate_storage (void)
 
   shiftset = XCALLOC (short, nsyms);
   redset = XCALLOC (short, nrules + 1);
-  state_table = XCALLOC (core *, STATE_TABLE_SIZE);
+  state_hash = XCALLOC (state_t *, STATE_HASH_SIZE);
 }
 
 
 static void
 free_storage (void)
 {
-  XFREE (shift_symbol);
-  XFREE (redset);
-  XFREE (shiftset);
-  XFREE (kernel_base);
-  XFREE (kernel_end);
+  free (shift_symbol);
+  free (redset);
+  free (shiftset);
+  free (kernel_base);
+  free (kernel_size);
   XFREE (kernel_items);
-  XFREE (state_table);
+  free (state_hash);
 }
 
 
@@ -132,45 +133,39 @@ free_storage (void)
 | shift_symbol is set to a vector of the symbols that can be      |
 | shifted.  For each symbol in the grammar, kernel_base[symbol]   |
 | points to a vector of item numbers activated if that symbol is  |
-| shifted, and kernel_end[symbol] points after the end of that    |
-| vector.                                                         |
+| shifted, and kernel_size[symbol] is their numbers.              |
 `----------------------------------------------------------------*/
 
 static void
 new_itemsets (void)
 {
   int i;
-  int shiftcount;
 
   if (trace_flag)
     fprintf (stderr, "Entering new_itemsets, state = %d\n",
 	     this_state->number);
 
   for (i = 0; i < nsyms; i++)
-    kernel_end[i] = NULL;
+    kernel_size[i] = 0;
 
-  shiftcount = 0;
+  shift_symbol = XCALLOC (short, nsyms);
+  nshifts = 0;
 
-  for (i = 0; i < itemsetend - itemset; ++i)
+  for (i = 0; i < nitemset; ++i)
     {
       int symbol = ritem[itemset[i]];
       if (symbol > 0)
 	{
-	  short *ksp = kernel_end[symbol];
-
-	  if (!ksp)
+	  if (!kernel_size[symbol])
 	    {
-	      shift_symbol[shiftcount] = symbol;
-	      ksp = kernel_base[symbol];
-	      shiftcount++;
+	      shift_symbol[nshifts] = symbol;
+	      nshifts++;
 	    }
 
-	  *ksp++ = itemset[i] + 1;
-	  kernel_end[symbol] = ksp;
+	  kernel_base[symbol][kernel_size[symbol]] = itemset[i] + 1;
+	  kernel_size[symbol]++;
 	}
     }
-
-  nshifts = shiftcount;
 }
 
 
@@ -180,11 +175,10 @@ new_itemsets (void)
 | necessary.                                                       |
 `-----------------------------------------------------------------*/
 
-static core *
+static state_t *
 new_state (int symbol)
 {
-  int n;
-  core *p;
+  state_t *p;
 
   if (trace_flag)
     fprintf (stderr, "Entering new_state, state = %d, symbol = %d (%s)\n",
@@ -193,14 +187,12 @@ new_state (int symbol)
   if (nstates >= MAXSHORT)
     fatal (_("too many states (max %d)"), MAXSHORT);
 
-  n = kernel_end[symbol] - kernel_base[symbol];
-
-  p = CORE_ALLOC (n);
+  p = STATE_ALLOC (kernel_size[symbol]);
   p->accessing_symbol = symbol;
   p->number = nstates;
-  p->nitems = n;
+  p->nitems = kernel_size[symbol];
 
-  shortcpy (p->items, kernel_base[symbol], n);
+  shortcpy (p->items, kernel_base[symbol], kernel_size[symbol]);
 
   last_state->next = p;
   last_state = p;
@@ -220,11 +212,8 @@ static int
 get_state (int symbol)
 {
   int key;
-  short *isp2;
   int i;
-  core *sp;
-
-  int n = kernel_end[symbol] - kernel_base[symbol];
+  state_t *sp;
 
   if (trace_flag)
     fprintf (stderr, "Entering get_state, state = %d, symbol = %d (%s)\n",
@@ -233,21 +222,20 @@ get_state (int symbol)
   /* Add up the target state's active item numbers to get a hash key.
      */
   key = 0;
-  for (i = 0; i < n; ++i)
+  for (i = 0; i < kernel_size[symbol]; ++i)
     key += kernel_base[symbol][i];
-  key = key % STATE_TABLE_SIZE;
-  sp = state_table[key];
+  key = key % STATE_HASH_SIZE;
+  sp = state_hash[key];
 
   if (sp)
     {
       int found = 0;
       while (!found)
 	{
-	  if (sp->nitems == n)
+	  if (sp->nitems == kernel_size[symbol])
 	    {
-	      int i;
 	      found = 1;
-	      for (i = 0; i < n; ++i)
+	      for (i = 0; i < kernel_size[symbol]; ++i)
 		if (kernel_base[symbol][i] != sp->items[i])
 		  found = 0;
 	    }
@@ -268,7 +256,7 @@ get_state (int symbol)
     }
   else				/* bucket is empty */
     {
-      state_table[key] = sp = new_state (symbol);
+      state_hash[key] = sp = new_state (symbol);
     }
 
   if (trace_flag)
@@ -317,20 +305,23 @@ append_states (void)
 static void
 new_states (void)
 {
-  first_state = last_state = this_state = CORE_ALLOC (0);
+  first_state = last_state = this_state = STATE_ALLOC (0);
   nstates = 1;
 }
 
 
+/*------------------------------------------------------------.
+| Save the NSHIFTS of SHIFTSET into the current linked list.  |
+`------------------------------------------------------------*/
+
 static void
 save_shifts (void)
 {
-  shifts *p = SHIFTS_ALLOC (nshifts);
+  shifts *p = shifts_new (nshifts);
 
   p->number = this_state->number;
-  p->nshifts = nshifts;
-
   shortcpy (p->shifts, shiftset, nshifts);
+  this_state->shifts = p;
 
   if (last_shift)
     last_shift->next = p;
@@ -343,25 +334,35 @@ save_shifts (void)
 /*------------------------------------------------------------------.
 | Subroutine of augment_automaton.  Create the next-to-final state, |
 | to which a shift has already been made in the initial state.      |
+|                                                                   |
+| The task of this state consists in shifting (actually, it's a     |
+| goto, but shifts and gotos are both stored in SHIFTS) the start   |
+| symbols, hence the name.                                          |
 `------------------------------------------------------------------*/
 
 static void
-insert_start_shift (void)
+insert_start_shifting_state (void)
 {
-  core *statep;
+  state_t *statep;
   shifts *sp;
 
-  statep = CORE_ALLOC (0);
+  statep = STATE_ALLOC (0);
   statep->number = nstates;
+
+  /* The distinctive feature of this state from the
+     eof_shifting_state, is that it is labeled as post-start-symbol
+     shifting.  I fail to understand why this state, and the
+     post-start-start can't be merged into one.  But it does fail if
+     you try. --akim */
   statep->accessing_symbol = start_symbol;
 
   last_state->next = statep;
   last_state = statep;
 
   /* Make a shift from this state to (what will be) the final state.  */
-  sp = SHIFTS_ALLOC (1);
+  sp = shifts_new (1);
+  statep->shifts = sp;
   sp->number = nstates++;
-  sp->nshifts = 1;
   sp->shifts[0] = nstates;
 
   last_shift->next = sp;
@@ -369,142 +370,80 @@ insert_start_shift (void)
 }
 
 
-/*------------------------------------------------------------------.
-| Make sure that the initial state has a shift that accepts the     |
-| grammar's start symbol and goes to the next-to-final state, which |
-| has a shift going to the final state, which has a shift to the    |
-| termination state.  Create such states and shifts if they don't   |
-| happen to exist already.                                          |
-`------------------------------------------------------------------*/
+/*-----------------------------------------------------------------.
+| Subroutine of augment_automaton.  Create the final state, which  |
+| shifts `0', the end of file.  The initial state shifts the start |
+| symbol, and goes to here.                                        |
+`-----------------------------------------------------------------*/
 
 static void
-augment_automaton (void)
+insert_eof_shifting_state (void)
 {
-  int i;
-  int k;
-  core *statep;
+  state_t *statep;
   shifts *sp;
-  shifts *sp2;
-  shifts *sp1 = NULL;
 
-  sp = first_shift;
+  /* Make the final state--the one that follows a shift from the
+     next-to-final state.
+     The symbol for that shift is 0 (end-of-file).  */
+  statep = STATE_ALLOC (0);
+  statep->number = nstates;
+
+  last_state->next = statep;
+  last_state = statep;
 
-  if (sp)
-    {
-      if (sp->number == 0)
-	{
-	  k = sp->nshifts;
-	  statep = first_state->next;
+  /* Make the shift from the final state to the termination state.  */
+  sp = shifts_new (1);
+  statep->shifts = sp;
+  sp->number = nstates++;
+  sp->shifts[0] = nstates;
 
-	  /* The states reached by shifts from first_state are numbered 1...K.
-	     Look for one reached by start_symbol.  */
-	  while (statep->accessing_symbol < start_symbol
-		 && statep->number < k)
-	    statep = statep->next;
+  last_shift->next = sp;
+  last_shift = sp;
+}
 
-	  if (statep->accessing_symbol == start_symbol)
-	    {
-	      /* We already have a next-to-final state.
-	         Make sure it has a shift to what will be the final state.  */
-	      k = statep->number;
 
-	      while (sp && sp->number < k)
-		{
-		  sp1 = sp;
-		  sp = sp->next;
-		}
+/*---------------------------------------------------------------.
+| Subroutine of augment_automaton.  Create the accepting state.  |
+`---------------------------------------------------------------*/
 
-	      if (sp && sp->number == k)
-		{
-		  sp2 = SHIFTS_ALLOC (sp->nshifts + 1);
-		  sp2->number = k;
-		  sp2->nshifts = sp->nshifts + 1;
-		  sp2->shifts[0] = nstates;
-		  for (i = sp->nshifts; i > 0; i--)
-		    sp2->shifts[i] = sp->shifts[i - 1];
-
-		  /* Patch sp2 into the chain of shifts in place of sp,
-		     following sp1.  */
-		  sp2->next = sp->next;
-		  sp1->next = sp2;
-		  if (sp == last_shift)
-		    last_shift = sp2;
-		  XFREE (sp);
-		}
-	      else
-		{
-		  sp2 = SHIFTS_ALLOC (1);
-		  sp2->number = k;
-		  sp2->nshifts = 1;
-		  sp2->shifts[0] = nstates;
-
-		  /* Patch sp2 into the chain of shifts between sp1 and sp.  */
-		  sp2->next = sp;
-		  sp1->next = sp2;
-		  if (sp == 0)
-		    last_shift = sp2;
-		}
-	    }
-	  else
-	    {
-	      /* There is no next-to-final state as yet.  */
-	      /* Add one more shift in first_shift,
-	         going to the next-to-final state (yet to be made).  */
-	      sp = first_shift;
+static void
+insert_accepting_state (void)
+{
+  state_t *statep;
 
-	      sp2 = SHIFTS_ALLOC (sp->nshifts + 1);
-	      sp2->nshifts = sp->nshifts + 1;
+   /* Note that the variable `final_state' refers to what we sometimes
+      call the termination state.  */
+  final_state = nstates;
 
-	      /* Stick this shift into the vector at the proper place.  */
-	      statep = first_state->next;
-	      for (k = 0, i = 0; i < sp->nshifts; k++, i++)
-		{
-		  if (statep->accessing_symbol > start_symbol && i == k)
-		    sp2->shifts[k++] = nstates;
-		  sp2->shifts[k] = sp->shifts[i];
-		  statep = statep->next;
-		}
-	      if (i == k)
-		sp2->shifts[k++] = nstates;
+  /* Make the termination state.  */
+  statep = STATE_ALLOC (0);
+  statep->number = nstates++;
+  last_state->next = statep;
+  last_state = statep;
+}
 
-	      /* Patch sp2 into the chain of shifts
-	         in place of sp, at the beginning.  */
-	      sp2->next = sp->next;
-	      first_shift = sp2;
-	      if (last_shift == sp)
-		last_shift = sp2;
 
-	      XFREE (sp);
 
-	      /* Create the next-to-final state, with shift to
-	         what will be the final state.  */
-	      insert_start_shift ();
-	    }
-	}
-      else
-	{
-	  /* The initial state didn't even have any shifts.
-	     Give it one shift, to the next-to-final state.  */
-	  sp = SHIFTS_ALLOC (1);
-	  sp->nshifts = 1;
-	  sp->shifts[0] = nstates;
-
-	  /* Patch sp into the chain of shifts at the beginning.  */
-	  sp->next = first_shift;
-	  first_shift = sp;
-
-	  /* Create the next-to-final state, with shift to
-	     what will be the final state.  */
-	  insert_start_shift ();
-	}
-    }
-  else
+
+
+/*------------------------------------------------------------------.
+| Make sure that the initial state has a shift that accepts the     |
+| grammar's start symbol and goes to the next-to-final state, which |
+| has a shift going to the final state, which has a shift to the    |
+| termination state.  Create such states and shifts if they don't   |
+| happen to exist already.                                          |
+`------------------------------------------------------------------*/
+
+static void
+augment_automaton (void)
+{
+  if (!first_state->shifts->nshifts)
     {
-      /* There are no shifts for any state.
-         Make one shift, from the initial state to the next-to-final state.  */
+      /* The first state has no shifts.  Make one shift, from the
+	 initial state to the next-to-final state.  */
 
-      sp = SHIFTS_ALLOC (1);
-      sp->nshifts = 1;
+      shifts *sp = shifts_new (1);
+      first_state->shifts = sp;
       sp->shifts[0] = nstates;
 
       /* Initialize the chain of shifts with sp.  */
@@ -513,34 +452,106 @@ augment_automaton (void)
 
       /* Create the next-to-final state, with shift to
          what will be the final state.  */
-      insert_start_shift ();
+      insert_start_shifting_state ();
     }
+  else
+    {
+      state_t *statep = first_state->next;
+      shifts *sp = first_state->shifts;
+      shifts *sp1 = NULL;
+      /* The states reached by shifts from FIRST_STATE are numbered
+	 1..(SP->NSHIFTS).  Look for one reached by START_SYMBOL.
+	 This is typical of `start: start ... ;': there is a state
+	 with the item `start: start . ...'.  We want to add a `shift
+	 on EOF to eof-shifting state here.  */
+      while (statep->accessing_symbol != start_symbol
+	     && statep->number < sp->nshifts)
+	statep = statep->next;
+
+      if (statep->accessing_symbol == start_symbol)
+	{
+	  /* We already have a next-to-final state, i.e., for `start:
+	     start . ...'.  Make sure it has a shift to what will be
+	     the final state.  */
+	  while (sp && sp->number < statep->number)
+	    {
+	      sp1 = sp;
+	      sp = sp->next;
+	    }
 
-  /* Make the final state--the one that follows a shift from the
-     next-to-final state.
-     The symbol for that shift is 0 (end-of-file).  */
-  statep = CORE_ALLOC (0);
-  statep->number = nstates;
-  last_state->next = statep;
-  last_state = statep;
+	  if (sp && sp->number == statep->number)
+	    {
+	      int i;
+	      shifts *sp2 = shifts_new (sp->nshifts + 1);
+	      sp2->number = statep->number;
+	      statep->shifts = sp2;
+	      sp2->shifts[0] = nstates;
+	      for (i = sp->nshifts; i > 0; i--)
+		sp2->shifts[i] = sp->shifts[i - 1];
+
+	      /* Patch sp2 into the chain of shifts in place of sp,
+		 following sp1.  */
+	      sp2->next = sp->next;
+	      sp1->next = sp2;
+	      if (sp == last_shift)
+		last_shift = sp2;
+	      XFREE (sp);
+	    }
+	  else
+	    {
+	      shifts *sp2 = shifts_new (1);
+	      sp2->number = statep->number;
+	      statep->shifts = sp2;
+	      sp2->shifts[0] = nstates;
+
+	      /* Patch sp2 into the chain of shifts between sp1 and sp.  */
+	      sp2->next = sp;
+	      sp1->next = sp2;
+	      if (sp == 0)
+		last_shift = sp2;
+	    }
+	  insert_eof_shifting_state ();
+	}
+      else
+	{
+	  /* There is no state for `start: start . ...'. */
+	  int i, k;
+	  shifts *sp2;
+	  sp = first_shift;
+
+	  /* There is no next-to-final state as yet.  */
+	  /* Add one more shift in first_shift,
+	     going to the next-to-final state (yet to be made).  */
+	  sp2 = shifts_new (sp->nshifts + 1);
+	  first_state->shifts = sp2;
+	  /* Stick this shift into the vector at the proper place.  */
+	  statep = first_state->next;
+	  for (k = 0, i = 0; i < sp->nshifts; k++, i++)
+	    {
+	      if (statep->accessing_symbol > start_symbol && i == k)
+		sp2->shifts[k++] = nstates;
+	      sp2->shifts[k] = sp->shifts[i];
+	      statep = statep->next;
+	    }
+	  if (i == k)
+	    sp2->shifts[k++] = nstates;
 
-  /* Make the shift from the final state to the termination state.  */
-  sp = SHIFTS_ALLOC (1);
-  sp->number = nstates++;
-  sp->nshifts = 1;
-  sp->shifts[0] = nstates;
-  last_shift->next = sp;
-  last_shift = sp;
+	  /* Patch sp2 into the chain of shifts
+	     in place of sp, at the beginning.  */
+	  sp2->next = sp->next;
+	  first_shift = sp2;
+	  if (last_shift == sp)
+	    last_shift = sp2;
 
-  /* Note that the variable `final_state' refers to what we sometimes call
-     the termination state.  */
-  final_state = nstates;
+	  XFREE (sp);
 
-  /* Make the termination state.  */
-  statep = CORE_ALLOC (0);
-  statep->number = nstates++;
-  last_state->next = statep;
-  last_state = statep;
+	  /* Create the next-to-final state, with shift to what will
+	     be the final state.  Corresponds to `start: start . ...'.  */
+	  insert_start_shifting_state ();
+	}
+    }
+
+  insert_accepting_state ();
 }
 
 
@@ -553,19 +564,15 @@ augment_automaton (void)
 static void
 save_reductions (void)
 {
-  short *isp;
-  int item;
   int count;
-  reductions *p;
-
-  short *rend;
+  int i;
 
   /* Find and count the active items that represent ends of rules. */
 
   count = 0;
-  for (isp = itemset; isp < itemsetend; isp++)
+  for (i = 0; i < nitemset; ++i)
     {
-      item = ritem[*isp];
+      int item = ritem[itemset[i]];
       if (item < 0)
 	redset[count++] = -item;
     }
@@ -574,22 +581,76 @@ save_reductions (void)
 
   if (count)
     {
-      p = REDUCTIONS_ALLOC (count);
-
-      p->number = this_state->number;
+      reductions *p = REDUCTIONS_ALLOC (count);
       p->nreds = count;
-
       shortcpy (p->rules, redset, count);
 
-      if (last_reduction)
-	last_reduction->next = p;
-      else
-	first_reduction = p;
-      last_reduction = p;
+      this_state->reductions = p;
     }
 }
 
 
+/*--------------------.
+| Build STATE_TABLE.  |
+`--------------------*/
+
+static void
+set_state_table (void)
+{
+  /* NSTATES + 1 because lookahead for the pseudo state number NSTATES
+     might be used (see conflicts.c).  It is too opaque for me to
+     provide a probably less hacky implementation. --akim */
+  state_table = XCALLOC (state_t *, nstates + 1);
+
+  {
+    state_t *sp;
+    for (sp = first_state; sp; sp = sp->next)
+      state_table[sp->number] = sp;
+  }
+
+  /* Pessimization, but simplification of the code: make sure all the
+     states have a shifts, even if reduced to 0 shifts.  */
+  {
+    int i;
+    for (i = 0; i < nstates; i++)
+      if (!state_table[i]->shifts)
+	state_table[i]->shifts = shifts_new (0);
+  }
+
+  /* Initializing the lookaheads members.  Please note that it must be
+     performed after having set some of the other members which are
+     used below.  Change with extreme caution.  */
+  {
+    int i;
+    int count = 0;
+    for (i = 0; i < nstates; i++)
+      {
+	int k;
+	reductions *rp = state_table[i]->reductions;
+	shifts *sp = state_table[i]->shifts;
+
+	state_table[i]->lookaheads = count;
+
+	if (rp
+	    && (rp->nreds > 1 || (sp->nshifts && SHIFT_IS_SHIFT (sp, 0))))
+	  count += rp->nreds;
+	else
+	  state_table[i]->consistent = 1;
+
+	for (k = 0; k < sp->nshifts; k++)
+	  if (SHIFT_IS_ERROR (sp, k))
+	    {
+	      state_table[i]->consistent = 0;
+	      break;
+	    }
+      }
+
+    /* Seems to be needed by conflicts.c. */
+    state_table[nstates] = STATE_ALLOC (0);
+    state_table[nstates]->lookaheads = count;
+  }
+}
+
 /*-------------------------------------------------------------------.
 | Compute the nondeterministic finite state machine (see state.h for |
 | details) from the grammar.                                         |
@@ -604,6 +665,9 @@ generate_states (void)
 
   while (this_state)
     {
+      if (trace_flag)
+	fprintf (stderr, "Processing state %d (reached by %s)\n",
+		 this_state->number, tags[this_state->accessing_symbol]);
       /* Set up ruleset and itemset for the transitions out of this
          state.  ruleset gets a 1 bit for each rule that could reduce
          now.  itemset gets a vector of all the items that could be
@@ -618,8 +682,7 @@ generate_states (void)
 
       /* create the shifts structures for the shifts to those states,
          now that the state numbers transitioning to are known */
-      if (nshifts > 0)
-	save_shifts ();
+      save_shifts ();
 
       /* states are queued when they are created; process them all */
       this_state = this_state->next;
@@ -631,4 +694,7 @@ generate_states (void)
 
   /* set up initial and final states as parser wants them */
   augment_automaton ();
+
+  /* Set up STATE_TABLE. */
+  set_state_table ();
 }