Turn misc objects into pseudovectors

Eliminate the category of miscellaneous objects, and turn all
such objects into pseudovectors.  The immediate motivation
for this change is to free up an enum Lisp_Type tag value, a
scarce resource that can be better used elsewhere.  However,
this change is worthwhile in its own right, as it improves
performance slightly on my platform, 0.3% faster for 'make
compile-always' on Fedora 28, and it simplifies the garbage
collector and interpreter (Bug#32405).
* doc/lispref/internals.texi (Garbage Collection):
* etc/NEWS:
Document change to garbage-collect return value.
* src/alloc.c (total_markers, total_free_markers):
(union aligned_Lisp_Misc, MARKER_BLOCK_SIZE)
(struct marker_block, marker_block, marker_block_index)
(misc_free_list, allocate_misc, live_misc_holding)
(live_misc_p, sweep_misc):
* src/lisp.h (lisp_h_MARKERP, lisp_h_MISCP, MARKERP, MISCP)
(Lisp_Misc, enum Lisp_Misc_Type, Lisp_Misc_Free)
(Lisp_Misc_Marker, Lisp_Misc_Overlay, Lisp_Misc_Finalizer)
(Lisp_Misc_Ptr, Lisp_Misc_User_Ptr, Lisp_Misc_Limit)
(Lisp_Misc_Bignum)
(XSETMISC, struct Lisp_Misc_Any, XMISCANY, XMISCTYPE)
(struct Lisp_Free, union Lisp_Misc, XMISC):
Remove.  All uses removed.
(cleanup_vector): Clean up objects that were formerly misc
and are now pseudovectors.
(make_misc_ptr, build_overlay, Fmake_marker, build_marker)
(make_bignum_str, make_number, make_pure_bignum)
(make_user_ptr, Fmake_finalizer):
Build as pseudovectors, not as misc objects.
(mark_finalizer_list, queue_doomed_finalizers)
(compact_undo_list, mark_overlay, mark_object)
(unchain_dead_markers):
Mark as vector-like objects, not as misc objects.
(mark_maybe_object, mark_maybe_pointer, valid_lisp_object_p)
(total_bytes_of_live_objects, survives_gc_p):
* src/fns.c (sxhash):
No need to worry about misc objects.
(garbage_collect_1): Do not generate a 'misc' component.
(syms_of_alloc): No need for 'misc' symbol.
* src/buffer.c (overlays_at, overlays_in, overlay_touches_p)
(overlay_strings, recenter_overlay_lists)
(fix_start_end_in_overlays, fix_overlays_before)
(Foverlay_lists, report_overlay_modification)
(evaporate_overlays):
* src/editfns.c (overlays_around):
* src/data.c (Ftype_of):
* src/fns.c (internal_equal):
* src/lisp.h (mint_ptrp, xmint_pointer, FINALIZERP)
(XFINALIZER, MARKERP, XMARKER, OVERLAYP, XOVERLAY, USER_PTRP)
(XUSER_PTR, BIGNUMP, XBIGNUM):
* src/print.c (print_vectorlike, print_object):
* src/undo.c (record_marker_adjustments):
* src/xdisp.c (load_overlay_strings):
Formerly misc objects are now pseudovectors.
* src/lisp.h (PVEC_MARKER, PVEC_OVERLAY, PVEC_FINALIZER)
(PVEC_BIGNUM, PVEC_MISC_PTR, PVEC_USER_PTR):
New constants, replacing their misc versions.  All uses changed.
(struct Lisp_Marker, struct Lisp_Overlay, struct Lisp_Misc_Ptr)
(struct Lisp_Bignum, struct Lisp_User_Ptr, struct Lisp_Finalizer):
Make usable as a pseudovector by using a pseudovector header,
replacing any DIY components, and putting Lisp_Object members
first.  All uses changed.

1 files changed, 110 insertions, 140 deletions

diff --git a/src/buffer.c b/src/buffer.c
index ec6f4647119..878844dd020 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2789,8 +2789,6 @@ overlays_at (EMACS_INT pos, bool extend, Lisp_Object **vec_ptr,
              ptrdiff_t *len_ptr,
              ptrdiff_t *next_ptr, ptrdiff_t *prev_ptr, bool change_req)
 {
-  Lisp_Object overlay, start, end;
-  struct Lisp_Overlay *tail;
   ptrdiff_t idx = 0;
   ptrdiff_t len = *len_ptr;
   Lisp_Object *vec = *vec_ptr;
@@ -2798,22 +2796,20 @@ overlays_at (EMACS_INT pos, bool extend, Lisp_Object **vec_ptr,
   ptrdiff_t prev = BEGV;
   bool inhibit_storing = 0;
 
-  for (tail = current_buffer->overlays_before; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+       tail; tail = tail->next)
     {
-      ptrdiff_t startpos, endpos;
-
-      XSETMISC (overlay, tail);
-
-      start = OVERLAY_START (overlay);
-      end = OVERLAY_END (overlay);
-      endpos = OVERLAY_POSITION (end);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+      Lisp_Object start = OVERLAY_START (overlay);
+      Lisp_Object end = OVERLAY_END (overlay);
+      ptrdiff_t endpos = OVERLAY_POSITION (end);
       if (endpos < pos)
         {
           if (prev < endpos)
             prev = endpos;
           break;
         }
-      startpos = OVERLAY_POSITION (start);
+      ptrdiff_t startpos = OVERLAY_POSITION (start);
       /* This one ends at or after POS
          so its start counts for PREV_PTR if it's before POS.  */
       if (prev < startpos && startpos < pos)
@@ -2846,22 +2842,20 @@ overlays_at (EMACS_INT pos, bool extend, Lisp_Object **vec_ptr,
         next = startpos;
     }
 
-  for (tail = current_buffer->overlays_after; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+       tail; tail = tail->next)
     {
-      ptrdiff_t startpos, endpos;
-
-      XSETMISC (overlay, tail);
-
-      start = OVERLAY_START (overlay);
-      end = OVERLAY_END (overlay);
-      startpos = OVERLAY_POSITION (start);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+      Lisp_Object start = OVERLAY_START (overlay);
+      Lisp_Object end = OVERLAY_END (overlay);
+      ptrdiff_t startpos = OVERLAY_POSITION (start);
       if (pos < startpos)
         {
           if (startpos < next)
             next = startpos;
           break;
         }
-      endpos = OVERLAY_POSITION (end);
+      ptrdiff_t endpos = OVERLAY_POSITION (end);
       if (pos < endpos)
         {
           if (idx == len)
@@ -2923,8 +2917,6 @@ overlays_in (EMACS_INT beg, EMACS_INT end, bool extend,
              Lisp_Object **vec_ptr, ptrdiff_t *len_ptr,
              ptrdiff_t *next_ptr, ptrdiff_t *prev_ptr)
 {
-  Lisp_Object overlay, ostart, oend;
-  struct Lisp_Overlay *tail;
   ptrdiff_t idx = 0;
   ptrdiff_t len = *len_ptr;
   Lisp_Object *vec = *vec_ptr;
@@ -2933,22 +2925,20 @@ overlays_in (EMACS_INT beg, EMACS_INT end, bool extend,
   bool inhibit_storing = 0;
   bool end_is_Z = end == Z;
 
-  for (tail = current_buffer->overlays_before; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+       tail; tail = tail->next)
     {
-      ptrdiff_t startpos, endpos;
-
-      XSETMISC (overlay, tail);
-
-      ostart = OVERLAY_START (overlay);
-      oend = OVERLAY_END (overlay);
-      endpos = OVERLAY_POSITION (oend);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+      Lisp_Object ostart = OVERLAY_START (overlay);
+      Lisp_Object oend = OVERLAY_END (overlay);
+      ptrdiff_t endpos = OVERLAY_POSITION (oend);
       if (endpos < beg)
         {
           if (prev < endpos)
             prev = endpos;
           break;
         }
-      startpos = OVERLAY_POSITION (ostart);
+      ptrdiff_t startpos = OVERLAY_POSITION (ostart);
       /* Count an interval if it overlaps the range, is empty at the
          start of the range, or is empty at END provided END denotes the
          end of the buffer.  */
@@ -2980,22 +2970,20 @@ overlays_in (EMACS_INT beg, EMACS_INT end, bool extend,
         next = startpos;
     }
 
-  for (tail = current_buffer->overlays_after; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+       tail; tail = tail->next)
     {
-      ptrdiff_t startpos, endpos;
-
-      XSETMISC (overlay, tail);
-
-      ostart = OVERLAY_START (overlay);
-      oend = OVERLAY_END (overlay);
-      startpos = OVERLAY_POSITION (ostart);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+      Lisp_Object ostart = OVERLAY_START (overlay);
+      Lisp_Object oend = OVERLAY_END (overlay);
+      ptrdiff_t startpos = OVERLAY_POSITION (ostart);
       if (end < startpos)
         {
           if (startpos < next)
             next = startpos;
           break;
         }
-      endpos = OVERLAY_POSITION (oend);
+      ptrdiff_t endpos = OVERLAY_POSITION (oend);
       /* Count an interval if it overlaps the range, is empty at the
          start of the range, or is empty at END provided END denotes the
          end of the buffer.  */
@@ -3097,31 +3085,26 @@ disable_line_numbers_overlay_at_eob (void)
 bool
 overlay_touches_p (ptrdiff_t pos)
 {
-  Lisp_Object overlay;
-  struct Lisp_Overlay *tail;
-
-  for (tail = current_buffer->overlays_before; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+       tail; tail = tail->next)
     {
-      ptrdiff_t endpos;
-
-      XSETMISC (overlay ,tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+      ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
       if (endpos < pos)
         break;
       if (endpos == pos || OVERLAY_POSITION (OVERLAY_START (overlay)) == pos)
         return 1;
     }
 
-  for (tail = current_buffer->overlays_after; tail; tail = tail->next)
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+       tail; tail = tail->next)
     {
-      ptrdiff_t startpos;
-
-      XSETMISC (overlay, tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+      ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
       if (pos < startpos)
         break;
       if (startpos == pos || OVERLAY_POSITION (OVERLAY_END (overlay)) == pos)
@@ -3337,27 +3320,26 @@ record_overlay_string (struct sortstrlist *ssl, Lisp_Object str,
 ptrdiff_t
 overlay_strings (ptrdiff_t pos, struct window *w, unsigned char **pstr)
 {
-  Lisp_Object overlay, window, str;
-  struct Lisp_Overlay *ov;
-  ptrdiff_t startpos, endpos;
   bool multibyte = ! NILP (BVAR (current_buffer, enable_multibyte_characters));
 
   overlay_heads.used = overlay_heads.bytes = 0;
   overlay_tails.used = overlay_tails.bytes = 0;
-  for (ov = current_buffer->overlays_before; ov; ov = ov->next)
+  for (struct Lisp_Overlay *ov = current_buffer->overlays_before;
+       ov; ov = ov->next)
     {
-      XSETMISC (overlay, ov);
+      Lisp_Object overlay = make_lisp_ptr (ov, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
-      endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+      ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+      ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
       if (endpos < pos)
         break;
       if (endpos != pos && startpos != pos)
         continue;
-      window = Foverlay_get (overlay, Qwindow);
+      Lisp_Object window = Foverlay_get (overlay, Qwindow);
       if (WINDOWP (window) && XWINDOW (window) != w)
         continue;
+      Lisp_Object str;
       if (startpos == pos
           && (str = Foverlay_get (overlay, Qbefore_string), STRINGP (str)))
         record_overlay_string (&overlay_heads, str,
@@ -3372,20 +3354,22 @@ overlay_strings (ptrdiff_t pos, struct window *w, unsigned char **pstr)
                                Foverlay_get (overlay, Qpriority),
                                endpos - startpos);
     }
-  for (ov = current_buffer->overlays_after; ov; ov = ov->next)
+  for (struct Lisp_Overlay *ov = current_buffer->overlays_after;
+       ov; ov = ov->next)
     {
-      XSETMISC (overlay, ov);
+      Lisp_Object overlay = make_lisp_ptr (ov, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
-      endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+      ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+      ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
       if (startpos > pos)
         break;
       if (endpos != pos && startpos != pos)
         continue;
-      window = Foverlay_get (overlay, Qwindow);
+      Lisp_Object window = Foverlay_get (overlay, Qwindow);
       if (WINDOWP (window) && XWINDOW (window) != w)
         continue;
+      Lisp_Object str;
       if (startpos == pos
           && (str = Foverlay_get (overlay, Qbefore_string), STRINGP (str)))
         record_overlay_string (&overlay_heads, str,
@@ -3460,8 +3444,7 @@ overlay_strings (ptrdiff_t pos, struct window *w, unsigned char **pstr)
 void
 recenter_overlay_lists (struct buffer *buf, ptrdiff_t pos)
 {
-  Lisp_Object overlay, beg, end;
-  struct Lisp_Overlay *prev, *tail, *next;
+  struct Lisp_Overlay *prev, *next;
 
   /* See if anything in overlays_before should move to overlays_after.  */
 
@@ -3469,14 +3452,15 @@ recenter_overlay_lists (struct buffer *buf, ptrdiff_t pos)
      But we use it for symmetry and in case that should cease to be true
      with some future change.  */
   prev = NULL;
-  for (tail = buf->overlays_before; tail; prev = tail, tail = next)
+  for (struct Lisp_Overlay *tail = buf->overlays_before;
+       tail; prev = tail, tail = next)
     {
       next = tail->next;
-      XSETMISC (overlay, tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      beg = OVERLAY_START (overlay);
-      end = OVERLAY_END (overlay);
+      Lisp_Object beg = OVERLAY_START (overlay);
+      Lisp_Object end = OVERLAY_END (overlay);
 
       if (OVERLAY_POSITION (end) > pos)
         {
@@ -3495,12 +3479,10 @@ recenter_overlay_lists (struct buffer *buf, ptrdiff_t pos)
           for (other = buf->overlays_after; other;
                other_prev = other, other = other->next)
             {
-              Lisp_Object otherbeg, otheroverlay;
-
-              XSETMISC (otheroverlay, other);
+              Lisp_Object otheroverlay = make_lisp_ptr (other, Lisp_Vectorlike);
               eassert (OVERLAYP (otheroverlay));
 
-              otherbeg = OVERLAY_START (otheroverlay);
+              Lisp_Object otherbeg = OVERLAY_START (otheroverlay);
               if (OVERLAY_POSITION (otherbeg) >= where)
                 break;
             }
@@ -3522,14 +3504,15 @@ recenter_overlay_lists (struct buffer *buf, ptrdiff_t pos)
 
   /* See if anything in overlays_after should be in overlays_before.  */
   prev = NULL;
-  for (tail = buf->overlays_after; tail; prev = tail, tail = next)
+  for (struct Lisp_Overlay *tail = buf->overlays_after;
+       tail; prev = tail, tail = next)
     {
       next = tail->next;
-      XSETMISC (overlay, tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
       eassert (OVERLAYP (overlay));
 
-      beg = OVERLAY_START (overlay);
-      end = OVERLAY_END (overlay);
+      Lisp_Object beg = OVERLAY_START (overlay);
+      Lisp_Object end = OVERLAY_END (overlay);
 
       /* Stop looking, when we know that nothing further
          can possibly end before POS.  */
@@ -3553,12 +3536,10 @@ recenter_overlay_lists (struct buffer *buf, ptrdiff_t pos)
           for (other = buf->overlays_before; other;
                other_prev = other, other = other->next)
             {
-              Lisp_Object otherend, otheroverlay;
-
-              XSETMISC (otheroverlay, other);
+              Lisp_Object otheroverlay = make_lisp_ptr (other, Lisp_Vectorlike);
               eassert (OVERLAYP (otheroverlay));
 
-              otherend = OVERLAY_END (otheroverlay);
+              Lisp_Object otherend = OVERLAY_END (otheroverlay);
               if (OVERLAY_POSITION (otherend) <= where)
                 break;
             }
@@ -3613,7 +3594,6 @@ adjust_overlays_for_delete (ptrdiff_t pos, ptrdiff_t length)
 void
 fix_start_end_in_overlays (register ptrdiff_t start, register ptrdiff_t end)
 {
-  Lisp_Object overlay;
   struct Lisp_Overlay *before_list UNINIT;
   struct Lisp_Overlay *after_list UNINIT;
   /* These are either nil, indicating that before_list or after_list
@@ -3623,8 +3603,7 @@ fix_start_end_in_overlays (register ptrdiff_t start, register ptrdiff_t end)
   /* 'Parent', likewise, indicates a cons cell or
      current_buffer->overlays_before or overlays_after, depending
      which loop we're in.  */
-  struct Lisp_Overlay *tail, *parent;
-  ptrdiff_t startpos, endpos;
+  struct Lisp_Overlay *parent;
 
   /* This algorithm shifts links around instead of consing and GCing.
      The loop invariant is that before_list (resp. after_list) is a
@@ -3633,12 +3612,14 @@ fix_start_end_in_overlays (register ptrdiff_t start, register ptrdiff_t end)
      (after_list) if it is, is still uninitialized.  So it's not a bug
      that before_list isn't initialized, although it may look
      strange.  */
-  for (parent = NULL, tail = current_buffer->overlays_before; tail;)
+  parent = NULL;
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+       tail; tail = tail->next)
     {
-      XSETMISC (overlay, tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
 
-      endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
-      startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+      ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+      ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
 
       /* If the overlay is backwards, make it empty.  */
       if (endpos < startpos)
@@ -3676,17 +3657,18 @@ fix_start_end_in_overlays (register ptrdiff_t start, register ptrdiff_t end)
             set_buffer_overlays_before (current_buffer, tail->next);
           else
             parent->next = tail->next;
-          tail = tail->next;
         }
       else
-        parent = tail, tail = parent->next;
+        parent = tail;
     }
-  for (parent = NULL, tail = current_buffer->overlays_after; tail;)
+  parent = NULL;
+  for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+       tail; tail = tail->next)
     {
-      XSETMISC (overlay, tail);
+      Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
 
-      startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
-      endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+      ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+      ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
 
       /* If the overlay is backwards, make it empty.  */
       if (endpos < startpos)
@@ -3722,10 +3704,9 @@ fix_start_end_in_overlays (register ptrdiff_t start, register ptrdiff_t end)
             set_buffer_overlays_after (current_buffer, tail->next);
           else
             parent->next = tail->next;
-          tail = tail->next;
         }
       else
-        parent = tail, tail = parent->next;
+        parent = tail;
     }
 
   /* Splice the constructed (wrong) lists into the buffer's lists,
@@ -3776,7 +3757,7 @@ fix_overlays_before (struct buffer *bp, ptrdiff_t prev, ptrdiff_t pos)
      overlay whose ending marker is after-insertion-marker if disorder
      exists).  */
   while (tail
-         && (XSETMISC (tem, tail),
+         && (tem = make_lisp_ptr (tail, Lisp_Vectorlike),
              (end = OVERLAY_POSITION (OVERLAY_END (tem))) >= pos))
     {
       parent = tail;
@@ -3801,7 +3782,7 @@ fix_overlays_before (struct buffer *bp, ptrdiff_t prev, ptrdiff_t pos)
      overlays are in correct order.  */
   while (tail)
     {
-      XSETMISC (tem, tail);
+      tem = make_lisp_ptr (tail, Lisp_Vectorlike);
       end = OVERLAY_POSITION (OVERLAY_END (tem));
 
       if (end == pos)
@@ -4308,19 +4289,14 @@ The lists you get are copies, so that changing them has no effect.
 However, the overlays you get are the real objects that the buffer uses.  */)
   (void)
 {
-  struct Lisp_Overlay *ol;
-  Lisp_Object before = Qnil, after = Qnil, tmp;
+  Lisp_Object before = Qnil, after = Qnil;
 
-  for (ol = current_buffer->overlays_before; ol; ol = ol->next)
-    {
-      XSETMISC (tmp, ol);
-      before = Fcons (tmp, before);
-    }
-  for (ol = current_buffer->overlays_after; ol; ol = ol->next)
-    {
-      XSETMISC (tmp, ol);
-      after = Fcons (tmp, after);
-    }
+  for (struct Lisp_Overlay *ol = current_buffer->overlays_before;
+       ol; ol = ol->next)
+    before = Fcons (make_lisp_ptr (ol, Lisp_Vectorlike), before);
+  for (struct Lisp_Overlay *ol = current_buffer->overlays_after;
+       ol; ol = ol->next)
+    after = Fcons (make_lisp_ptr (ol, Lisp_Vectorlike), after);
 
   return Fcons (Fnreverse (before), Fnreverse (after));
 }
@@ -4439,14 +4415,9 @@ void
 report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
                              Lisp_Object arg1, Lisp_Object arg2, Lisp_Object arg3)
 {
-  Lisp_Object prop, overlay;
-  struct Lisp_Overlay *tail;
   /* True if this change is an insertion.  */
   bool insertion = (after ? XFIXNAT (arg3) == 0 : EQ (start, end));
 
-  overlay = Qnil;
-  tail = NULL;
-
   /* We used to run the functions as soon as we found them and only register
      them in last_overlay_modification_hooks for the purpose of the `after'
      case.  But running elisp code as we traverse the list of overlays is
@@ -4460,12 +4431,13 @@ report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
       /* We are being called before a change.
          Scan the overlays to find the functions to call.  */
       last_overlay_modification_hooks_used = 0;
-      for (tail = current_buffer->overlays_before; tail; tail = tail->next)
+      for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+           tail; tail = tail->next)
         {
           ptrdiff_t startpos, endpos;
           Lisp_Object ostart, oend;
 
-          XSETMISC (overlay, tail);
+          Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
 
           ostart = OVERLAY_START (overlay);
           oend = OVERLAY_END (overlay);
@@ -4476,14 +4448,14 @@ report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
           if (insertion && (XFIXNAT (start) == startpos
                             || XFIXNAT (end) == startpos))
             {
-              prop = Foverlay_get (overlay, Qinsert_in_front_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qinsert_in_front_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
           if (insertion && (XFIXNAT (start) == endpos
                             || XFIXNAT (end) == endpos))
             {
-              prop = Foverlay_get (overlay, Qinsert_behind_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qinsert_behind_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
@@ -4491,18 +4463,19 @@ report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
              for both insertion and deletion.  */
           if (XFIXNAT (end) > startpos && XFIXNAT (start) < endpos)
             {
-              prop = Foverlay_get (overlay, Qmodification_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qmodification_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
         }
 
-      for (tail = current_buffer->overlays_after; tail; tail = tail->next)
+      for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+           tail; tail = tail->next)
         {
           ptrdiff_t startpos, endpos;
           Lisp_Object ostart, oend;
 
-          XSETMISC (overlay, tail);
+          Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
 
           ostart = OVERLAY_START (overlay);
           oend = OVERLAY_END (overlay);
@@ -4513,14 +4486,14 @@ report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
           if (insertion && (XFIXNAT (start) == startpos
                             || XFIXNAT (end) == startpos))
             {
-              prop = Foverlay_get (overlay, Qinsert_in_front_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qinsert_in_front_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
           if (insertion && (XFIXNAT (start) == endpos
                             || XFIXNAT (end) == endpos))
             {
-              prop = Foverlay_get (overlay, Qinsert_behind_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qinsert_behind_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
@@ -4528,7 +4501,7 @@ report_overlay_modification (Lisp_Object start, Lisp_Object end, bool after,
              for both insertion and deletion.  */
           if (XFIXNAT (end) > startpos && XFIXNAT (start) < endpos)
             {
-              prop = Foverlay_get (overlay, Qmodification_hooks);
+              Lisp_Object prop = Foverlay_get (overlay, Qmodification_hooks);
               if (!NILP (prop))
                 add_overlay_mod_hooklist (prop, overlay);
             }
@@ -4596,16 +4569,13 @@ call_overlay_mod_hooks (Lisp_Object list, Lisp_Object overlay, bool after,
 void
 evaporate_overlays (ptrdiff_t pos)
 {
-  Lisp_Object overlay, hit_list;
-  struct Lisp_Overlay *tail;
-
-  hit_list = Qnil;
+  Lisp_Object hit_list = Qnil;
   if (pos <= current_buffer->overlay_center)
-    for (tail = current_buffer->overlays_before; tail; tail = tail->next)
+    for (struct Lisp_Overlay *tail = current_buffer->overlays_before;
+         tail; tail = tail->next)
       {
-        ptrdiff_t endpos;
-        XSETMISC (overlay, tail);
-        endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
+        Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+        ptrdiff_t endpos = OVERLAY_POSITION (OVERLAY_END (overlay));
         if (endpos < pos)
           break;
         if (endpos == pos && OVERLAY_POSITION (OVERLAY_START (overlay)) == pos
@@ -4613,11 +4583,11 @@ evaporate_overlays (ptrdiff_t pos)
           hit_list = Fcons (overlay, hit_list);
       }
   else
-    for (tail = current_buffer->overlays_after; tail; tail = tail->next)
+    for (struct Lisp_Overlay *tail = current_buffer->overlays_after;
+         tail; tail = tail->next)
       {
-        ptrdiff_t startpos;
-        XSETMISC (overlay, tail);
-        startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
+        Lisp_Object overlay = make_lisp_ptr (tail, Lisp_Vectorlike);
+        ptrdiff_t startpos = OVERLAY_POSITION (OVERLAY_START (overlay));
         if (startpos > pos)
           break;
         if (startpos == pos && OVERLAY_POSITION (OVERLAY_END (overlay)) == pos