X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/0ab3728b128584655dec71591b8e5ba0093baece..4ec8e00f609b4a44c3c9e5a25c82706b393a0e16:/src/LR0.c

diff --git a/src/LR0.c b/src/LR0.c
index 7770ecbc..5e8caef0 100644
--- a/src/LR0.c
+++ b/src/LR0.c
@@ -35,12 +35,10 @@
 
 int nstates;
 int final_state;
-state_t *first_state = NULL;
-shifts *first_shift = NULL;
+static state_t *first_state = NULL;
 
 static state_t *this_state = NULL;
 static state_t *last_state = NULL;
-static shifts *last_shift = NULL;
 
 static int nshifts;
 static short *shift_symbol = NULL;
@@ -318,16 +316,8 @@ static void
 save_shifts (void)
 {
   shifts *p = shifts_new (nshifts);
-
-  p->number = this_state->number;
-
   shortcpy (p->shifts, shiftset, nshifts);
-
-  if (last_shift)
-    last_shift->next = p;
-  else
-    first_shift = p;
-  last_shift = p;
+  this_state->shifts = p;
 }
 
 
@@ -347,7 +337,7 @@ insert_start_shifting_state (void)
   shifts *sp;
 
   statep = STATE_ALLOC (0);
-  statep->number = nstates;
+  statep->number = nstates++;
 
   /* The distinctive feature of this state from the
      eof_shifting_state, is that it is labeled as post-start-symbol
@@ -361,11 +351,8 @@ insert_start_shifting_state (void)
 
   /* Make a shift from this state to (what will be) the final state.  */
   sp = shifts_new (1);
-  sp->number = nstates++;
+  statep->shifts = sp;
   sp->shifts[0] = nstates;
-
-  last_shift->next = sp;
-  last_shift = sp;
 }
 
 
@@ -385,18 +372,15 @@ insert_eof_shifting_state (void)
      next-to-final state.
      The symbol for that shift is 0 (end-of-file).  */
   statep = STATE_ALLOC (0);
-  statep->number = nstates;
+  statep->number = nstates++;
 
   last_state->next = statep;
   last_state = statep;
 
   /* Make the shift from the final state to the termination state.  */
   sp = shifts_new (1);
-  sp->number = nstates++;
+  statep->shifts = sp;
   sp->shifts[0] = nstates;
-
-  last_shift->next = sp;
-  last_shift = sp;
 }
 
 
@@ -435,127 +419,82 @@ insert_accepting_state (void)
 static void
 augment_automaton (void)
 {
-  if (!first_shift->nshifts)
+  if (!first_state->shifts->nshifts)
     {
-      /* There are no shifts for any state.  Make one shift, from the
+      /* The first state has no shifts.  Make one shift, from the
 	 initial state to the next-to-final state.  */
 
       shifts *sp = shifts_new (1);
+      first_state->shifts = sp;
       sp->shifts[0] = nstates;
 
-      /* Initialize the chain of shifts with sp.  */
-      first_shift = sp;
-      last_shift = sp;
-
       /* Create the next-to-final state, with shift to
          what will be the final state.  */
       insert_start_shifting_state ();
     }
-  else if (first_shift->number == 0)
+  else
     {
       state_t *statep = first_state->next;
-      shifts *sp = first_shift;
-      shifts *sp1 = NULL;
       /* The states reached by shifts from FIRST_STATE are numbered
-	 1..(SP->NSHIFTS).  Look for one reached by START_SYMBOL.  */
+	 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->number < first_state->shifts->nshifts)
 	statep = statep->next;
 
       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.  */
-	  while (sp && sp->number < statep->number)
-	    {
-	      sp1 = sp;
-	      sp = sp->next;
-	    }
+	  /* We already have STATEP, a next-to-final state for `start:
+	     start . ...'.  Make sure it has a shift to what will be
+	     the final state.  */
+	  int i;
 
-	  if (sp && sp->number == statep->number)
-	    {
-	      int i;
-	      shifts *sp2 = shifts_new (sp->nshifts + 1);
-	      sp2->number = statep->number;
-	      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;
-	      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;
-	    }
+	  /* Find the shift of the inital state that leads to STATEP.  */
+	  shifts *sp = statep->shifts;
+
+	  shifts *sp1 = shifts_new (sp->nshifts + 1);
+	  statep->shifts = sp1;
+	  sp1->shifts[0] = nstates;
+	  for (i = sp->nshifts; i > 0; i--)
+	    sp1->shifts[i] = sp->shifts[i - 1];
+
+	  XFREE (sp);
+
+	  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);
+	  shifts *sp = first_state->shifts;
+	  shifts *sp1 = NULL;
 
+	  /* Add one more shift to the initial state, going to the
+	     next-to-final state (yet to be made).  */
+	  sp1 = shifts_new (sp->nshifts + 1);
+	  first_state->shifts = sp1;
 	  /* 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];
+		sp1->shifts[k++] = nstates;
+	      sp1->shifts[k] = sp->shifts[i];
 	      statep = statep->next;
 	    }
 	  if (i == k)
-	    sp2->shifts[k++] = nstates;
-
-	  /* 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;
+	    sp1->shifts[k++] = nstates;
 
 	  XFREE (sp);
 
-	  /* Create the next-to-final state, with shift to
-	     what will be the final state.  */
+	  /* Create the next-to-final state, with shift to what will
+	     be the final state.  Corresponds to `start: start . ...'.  */
 	  insert_start_shifting_state ();
 	}
     }
-  else
-    {
-      /* The initial state didn't even have any shifts.
-	 Give it one shift, to the next-to-final state.  */
-      shifts *sp = shifts_new (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_shifting_state ();
-    }
 
-  insert_eof_shifting_state ();
   insert_accepting_state ();
 }
 
@@ -595,6 +534,34 @@ save_reductions (void)
 }
 
 
+/*--------------------.
+| 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);
+  }
+}
+
 /*-------------------------------------------------------------------.
 | Compute the nondeterministic finite state machine (see state.h for |
 | details) from the grammar.                                         |
@@ -638,4 +605,7 @@ generate_states (void)
 
   /* set up initial and final states as parser wants them */
   augment_automaton ();
+
+  /* Set up STATE_TABLE. */
+  set_state_table ();
 }