Remove redundant checks for the empty overlay treefeature/noverlay

* src/alloc.c (mark_buffer): Remove b->overlays check.
* src/buffer.c (copy_overlays): Also.
* src/buffer.c (swap_buffer_overlays, overlays_in): Also.
  (next_overlay_change, previous_overlay_change): Also.
  (overlay_touches_p, Foverlay_lists): Also.
  (evaporate_overlays): Also.
* src/xdisp.c (load_overlay_strings): Also.

3 files changed, 62 insertions, 97 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 15a6fc43b72..9f72f914e00 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6306,15 +6306,11 @@ mark_buffer (struct buffer *buffer)
      a special way just before the sweep phase, and after stripping
      some of its elements that are not needed any more.  */
 
-  if (buffer->overlays)
-    {
-      struct interval_node *node;
-      buffer_overlay_iter_start (buffer, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
-
-      while ((node = buffer_overlay_iter_next (buffer)))
-        mark_overlay (XOVERLAY (node->data));
-      buffer_overlay_iter_finish (buffer);
-    }
+  struct interval_node *node;
+  buffer_overlay_iter_start (buffer, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
+  while ((node = buffer_overlay_iter_next (buffer)))
+    mark_overlay (XOVERLAY (node->data));
+  buffer_overlay_iter_finish (buffer);
 
   /* If this is an indirect buffer, mark its base buffer.  */
   if (buffer->base_buffer && !VECTOR_MARKED_P (buffer->base_buffer))
diff --git a/src/buffer.c b/src/buffer.c
index 122c60fab39..9ddc9c7e056 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -607,14 +607,9 @@ static void
 copy_overlays (struct buffer *from, struct buffer *to)
 {
   eassert (to && ! to->overlays);
-
   struct interval_node *node;
 
-  if (! from->overlays)
-    return;
-
   buffer_overlay_iter_start (from, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
-
   while ((node = buffer_overlay_iter_next (from)))
     {
       Lisp_Object ov = node->data;
@@ -2277,20 +2272,16 @@ swap_buffer_overlays (struct buffer *buffer, struct buffer *other)
 {
   struct interval_node *node;
 
-  if (buffer->overlays)
-    {
-      buffer_overlay_iter_start  (buffer, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
-      while ((node = buffer_overlay_iter_next (buffer)))
-        XOVERLAY (node->data)->buffer = other;
-      buffer_overlay_iter_finish (buffer);
-    }
-  if (other->overlays)
-    {
-      buffer_overlay_iter_start (other, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
-      while ((node = buffer_overlay_iter_next (other)))
-        XOVERLAY (node->data)->buffer = buffer;
-      buffer_overlay_iter_finish (other);
-    }
+  buffer_overlay_iter_start  (buffer, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
+  while ((node = buffer_overlay_iter_next (buffer)))
+    XOVERLAY (node->data)->buffer = other;
+  buffer_overlay_iter_finish (buffer);
+
+  buffer_overlay_iter_start (other, PTRDIFF_MIN, PTRDIFF_MAX, ITREE_ASCENDING);
+  while ((node = buffer_overlay_iter_next (other)))
+    XOVERLAY (node->data)->buffer = buffer;
+  buffer_overlay_iter_finish (other);
+
   /* Swap the interval trees. */
   void *tmp = buffer->overlays;
   buffer->overlays = other->overlays;
@@ -2837,12 +2828,8 @@ overlays_in (ptrdiff_t beg, ptrdiff_t end, bool extend,
   ptrdiff_t len = *len_ptr;
   ptrdiff_t next = ZV;
   Lisp_Object *vec = *vec_ptr;
-
   struct interval_node *node;
 
-  if (! current_buffer->overlays)
-    return idx;
-
   buffer_overlay_iter_start (current_buffer, beg,
                              /* Find empty OV at Z ? */
                              (end >= Z && empty) ? Z + 1 : ZV,
@@ -2904,9 +2891,6 @@ next_overlay_change (ptrdiff_t pos)
   ptrdiff_t next = ZV;
   struct interval_node *node;
 
-  if (! current_buffer->overlays)
-    return next;
-
   buffer_overlay_iter_start (current_buffer, pos, ZV, ITREE_ASCENDING);
   while ((node = buffer_overlay_iter_next (current_buffer)))
     {
@@ -2935,9 +2919,6 @@ previous_overlay_change (ptrdiff_t pos)
   struct interval_node *node;
   ptrdiff_t prev = BEGV;
 
-  if (! current_buffer->overlays)
-    return prev;
-
   buffer_overlay_iter_start (current_buffer, BEGV, pos, ITREE_DESCENDING);
   while ((node = buffer_overlay_iter_next (current_buffer)))
     {
@@ -3023,9 +3004,6 @@ overlay_touches_p (ptrdiff_t pos)
   struct interval_node *node;
   bool result = false;
 
-  if (! current_buffer->overlays)
-    return false;
-
   /* We need to find overlays ending in pos, as well as empty ones at
      pos. */
   buffer_overlay_iter_start (current_buffer,
@@ -3729,16 +3707,13 @@ However, the overlays you get are the real objects that the buffer uses. */)
   (void)
 {
   Lisp_Object overlays = Qnil;
+  struct interval_node *node;
 
-  if (current_buffer->overlays)
-    {
-      struct interval_node *node;
+  buffer_overlay_iter_start (current_buffer, BEG, Z, ITREE_DESCENDING);
+  while ((node = buffer_overlay_iter_next (current_buffer)))
+    overlays = Fcons (node->data, overlays);
+  buffer_overlay_iter_finish (current_buffer);
 
-      buffer_overlay_iter_start (current_buffer, BEG, Z, ITREE_DESCENDING);
-      while ((node = buffer_overlay_iter_next (current_buffer)))
-        overlays = Fcons (node->data, overlays);
-      buffer_overlay_iter_finish (current_buffer);
-    }
   return Fcons (overlays, Qnil);
 }
 
@@ -3972,15 +3947,10 @@ call_overlay_mod_hooks (Lisp_Object list, Lisp_Object overlay, bool after,
 void
 evaporate_overlays (ptrdiff_t pos)
 {
-  Lisp_Object hit_list;
+  Lisp_Object hit_list = Qnil;
   struct interval_node *node;
 
-  if (! current_buffer->overlays)
-    return;
-
-  hit_list = Qnil;
   buffer_overlay_iter_start (current_buffer, pos, pos, ITREE_ASCENDING);
-
   while ((node = buffer_overlay_iter_next (current_buffer)))
     {
       if (node->end == pos
@@ -3988,6 +3958,7 @@ evaporate_overlays (ptrdiff_t pos)
         hit_list = Fcons (node->data, hit_list);
     }
   buffer_overlay_iter_finish (current_buffer);
+
   for (; CONSP (hit_list); hit_list = XCDR (hit_list))
     Fdelete_overlay (XCAR (hit_list));
 }
diff --git a/src/xdisp.c b/src/xdisp.c
index b3b9ecae377..f94643b1f7b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -5790,48 +5790,46 @@ load_overlay_strings (struct it *it, ptrdiff_t charpos)
     }									\
   while (false)
 
-  if (current_buffer->overlays)
-    {
-      buffer_overlay_iter_start (current_buffer,
-                                 charpos - 1, charpos + 1, ITREE_DESCENDING);
-      /* Process overlays.  */
-      while ((node = buffer_overlay_iter_next (current_buffer)))
-        {
-          overlay = node->data;
-          eassert (OVERLAYP (overlay));
-          start = node->begin;
-          end = node->end;
-
-          /* Skip this overlay if it doesn't start or end at IT's current
-             position.  */
-          if (end != charpos && start != charpos)
-            continue;
-
-          /* Skip this overlay if it doesn't apply to IT->w.  */
-          window = Foverlay_get (overlay, Qwindow);
-          if (WINDOWP (window) && XWINDOW (window) != it->w)
-            continue;
-
-          /* If the text ``under'' the overlay is invisible, both before-
-             and after-strings from this overlay are visible; start and
-             end position are indistinguishable.  */
-          invisible = Foverlay_get (overlay, Qinvisible);
-          invis = TEXT_PROP_MEANS_INVISIBLE (invisible);
-
-          /* If overlay has a non-empty before-string, record it.  */
-          if ((start == charpos || (end == charpos && invis != 0))
-              && (str = Foverlay_get (overlay, Qbefore_string), STRINGP (str))
-              && SCHARS (str))
-            RECORD_OVERLAY_STRING (overlay, str, false);
-
-          /* If overlay has a non-empty after-string, record it.  */
-          if ((end == charpos || (start == charpos && invis != 0))
-              && (str = Foverlay_get (overlay, Qafter_string), STRINGP (str))
-              && SCHARS (str))
-            RECORD_OVERLAY_STRING (overlay, str, true);
-        }
-      buffer_overlay_iter_finish (current_buffer);
-    }
+
+  buffer_overlay_iter_start (current_buffer,
+                             charpos - 1, charpos + 1, ITREE_DESCENDING);
+  /* Process overlays.  */
+  while ((node = buffer_overlay_iter_next (current_buffer)))
+    {
+      overlay = node->data;
+      eassert (OVERLAYP (overlay));
+      start = node->begin;
+      end = node->end;
+
+      /* Skip this overlay if it doesn't start or end at IT's current
+         position.  */
+      if (end != charpos && start != charpos)
+        continue;
+
+      /* Skip this overlay if it doesn't apply to IT->w.  */
+      window = Foverlay_get (overlay, Qwindow);
+      if (WINDOWP (window) && XWINDOW (window) != it->w)
+        continue;
+
+      /* If the text ``under'' the overlay is invisible, both before-
+         and after-strings from this overlay are visible; start and
+         end position are indistinguishable.  */
+      invisible = Foverlay_get (overlay, Qinvisible);
+      invis = TEXT_PROP_MEANS_INVISIBLE (invisible);
+
+      /* If overlay has a non-empty before-string, record it.  */
+      if ((start == charpos || (end == charpos && invis != 0))
+          && (str = Foverlay_get (overlay, Qbefore_string), STRINGP (str))
+          && SCHARS (str))
+        RECORD_OVERLAY_STRING (overlay, str, false);
+
+      /* If overlay has a non-empty after-string, record it.  */
+      if ((end == charpos || (start == charpos && invis != 0))
+          && (str = Foverlay_get (overlay, Qafter_string), STRINGP (str))
+          && SCHARS (str))
+        RECORD_OVERLAY_STRING (overlay, str, true);
+    }
+  buffer_overlay_iter_finish (current_buffer);
 
 #undef RECORD_OVERLAY_STRING