don't try and free what must be a null vector when reserving 0 elements

in va_heap::reserve

2013-11-05  Trevor Saunders  <tsaunders@mozilla.com>

	* vec.c (vec_prefix::calculate_allocation): Don't try to handle the
	case of no prefix and reserving zero slots, because when that's the
	case we'll never get here.
	* vec.h (va_heap::reserve): Don't try and handle
	vec_prefix::calculate_allocation returning zero because that should
	never happen.

From-SVN: r204392

gcc/ChangeLog

+2013-11-05  Trevor Saunders  <tsaunders@mozilla.com>
+
+	* vec.c (vec_prefix::calculate_allocation): Don't try to handle the
+	case of no prefix and reserving zero slots, because when that's the
+	case we'll never get here.
+	* vec.h (va_heap::reserve): Don't try and handle
+	vec_prefix::calculate_allocation returning zero because that should
+	never happen.
+
 2013-11-05  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/58941

gcc/vec.c

@@ -187,9 +187,7 @@ vec_prefix::calculate_allocation (vec_prefix *pfx, unsigned reserve,
       num = pfx->m_num;
     }
   else if (!reserve)
-    /* If there's no vector, and we've not requested anything, then we
-       will create a NULL vector.  */
-    return 0;
+    gcc_unreachable ();
 
   /* We must have run out of room.  */
   gcc_assert (alloc - num < reserve);

gcc/vec.h

@@ -283,11 +283,7 @@ va_heap::reserve (vec<T, va_heap, vl_embed> *&v, unsigned reserve, bool exact
 {
   unsigned alloc
     = vec_prefix::calculate_allocation (v ? &v->m_vecpfx : 0, reserve, exact);
-  if (!alloc)
-    {
-      release (v);
-      return;
-    }
+  gcc_assert (alloc);
 
   if (GATHER_STATISTICS && v)
     v->m_vecpfx.release_overhead ();