Merge pull request #5913 from mhinz/buf-lookup-patches

vim-patch:7.4.2017,7.4.2018,7.4.2021,7.4.2022,7.4.2023,7.4.2024

21 files changed, 471 insertions, 301 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index eaaae943d2..738a5ae091 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -290,7 +290,6 @@ void nvim_buf_set_lines(uint64_t channel_id,
     return;
   }
 
-  buf_T *save_curbuf = NULL;
   win_T *save_curwin = NULL;
   tabpage_T *save_curtab = NULL;
   size_t new_len = replacement.size;
@@ -322,6 +321,7 @@ void nvim_buf_set_lines(uint64_t channel_id,
   }
 
   try_start();
+  bufref_T save_curbuf = { NULL, 0 };
   switch_to_win_for_buf(buf, &save_curwin, &save_curtab, &save_curbuf);
 
   if (u_save((linenr_T)(start - 1), (linenr_T)end) == FAIL) {
@@ -389,7 +389,7 @@ void nvim_buf_set_lines(uint64_t channel_id,
   // changed range, and move any in the remainder of the buffer.
   // Only adjust marks if we managed to switch to a window that holds
   // the buffer, otherwise line numbers will be invalid.
-  if (save_curbuf == NULL) {
+  if (save_curbuf.br_buf == NULL) {
     mark_adjust((linenr_T)start, (linenr_T)(end - 1), MAXLNUM, extra);
   }
 
@@ -405,7 +405,7 @@ end:
   }
 
   xfree(lines);
-  restore_win_for_buf(save_curwin, save_curtab, save_curbuf);
+  restore_win_for_buf(save_curwin, save_curtab, &save_curbuf);
   try_end(err);
 }
 
@@ -651,13 +651,13 @@ ArrayOf(Integer, 2) nvim_buf_get_mark(Buffer buffer, String name, Error *err)
   }
 
   pos_T *posp;
-  buf_T *savebuf;
   char mark = *name.data;
 
   try_start();
-  switch_buffer(&savebuf, buf);
+  bufref_T save_buf;
+  switch_buffer(&save_buf, buf);
   posp = getmark(mark, false);
-  restore_buffer(savebuf);
+  restore_buffer(&save_buf);
 
   if (try_end(err)) {
     return rv;
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 7daa4d7207..6f3f654bdc 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -899,7 +899,7 @@ static void set_option_value_for(char *key,
 {
   win_T *save_curwin = NULL;
   tabpage_T *save_curtab = NULL;
-  buf_T *save_curbuf = NULL;
+  bufref_T save_curbuf =  { NULL, 0 };
 
   try_start();
   switch (opt_type)
@@ -922,7 +922,7 @@ static void set_option_value_for(char *key,
     case SREQ_BUF:
       switch_buffer(&save_curbuf, (buf_T *)from);
       set_option_value_err(key, numval, stringval, opt_flags, err);
-      restore_buffer(save_curbuf);
+      restore_buffer(&save_curbuf);
       break;
     case SREQ_GLOBAL:
       set_option_value_err(key, numval, stringval, opt_flags, err);
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 868e842ecd..1089a2dc3b 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -78,6 +78,9 @@ static char *msg_loclist = N_("[Location List]");
 static char *msg_qflist = N_("[Quickfix List]");
 static char *e_auabort = N_("E855: Autocommands caused command to abort");
 
+// Number of times free_buffer() was called.
+static int buf_free_count = 0;
+
 /*
  * Open current buffer, that is: open the memfile and read the file into
  * memory.
@@ -91,7 +94,7 @@ open_buffer (
 )
 {
   int retval = OK;
-  buf_T       *old_curbuf;
+  bufref_T       old_curbuf;
   long old_tw = curbuf->b_p_tw;
 
   /*
@@ -133,10 +136,10 @@ open_buffer (
     return FAIL;
   }
 
-  /* The autocommands in readfile() may change the buffer, but only AFTER
-   * reading the file. */
-  old_curbuf = curbuf;
-  modified_was_set = FALSE;
+  // The autocommands in readfile() may change the buffer, but only AFTER
+  // reading the file.
+  set_bufref(&old_curbuf, curbuf);
+  modified_was_set = false;
 
   /* mark cursor position as being invalid */
   curwin->w_valid = 0;
@@ -249,11 +252,11 @@ open_buffer (
    * The autocommands may have changed the current buffer.  Apply the
    * modelines to the correct buffer, if it still exists and is loaded.
    */
-  if (buf_valid(old_curbuf) && old_curbuf->b_ml.ml_mfp != NULL) {
+  if (bufref_valid(&old_curbuf) && old_curbuf.br_buf->b_ml.ml_mfp != NULL) {
     aco_save_T aco;
 
-    /* Go to the buffer that was opened. */
-    aucmd_prepbuf(&aco, old_curbuf);
+    // Go to the buffer that was opened.
+    aucmd_prepbuf(&aco, old_curbuf.br_buf);
     do_modelines(0);
     curbuf->b_flags &= ~(BF_CHECK_RO | BF_NEVERLOADED);
 
@@ -267,14 +270,42 @@ open_buffer (
   return retval;
 }
 
-/// Check that "buf" points to a valid buffer (in the buffer list).
+/// Store "buf" in "bufref" and set the free count.
+///
+/// @param bufref Reference to be used for the buffer.
+/// @param buf    The buffer to reference.
+void set_bufref(bufref_T *bufref, buf_T *buf)
+{
+  bufref->br_buf = buf;
+  bufref->br_buf_free_count = buf_free_count;
+}
+
+/// Check if "bufref" points to a valid buffer.
+///
+/// Only goes through the buffer list if buf_free_count changed.
+///
+/// @param bufref Buffer reference to check for.
+bool bufref_valid(bufref_T *bufref)
+{
+  return bufref->br_buf_free_count == buf_free_count
+    ? true
+    : buf_valid(bufref->br_buf);
+}
+
+/// Check that "buf" points to a valid buffer in the buffer list.
+///
+/// Can be slow if there are many buffers, prefer using bufref_valid().
+///
+/// @param buf The buffer to check for.
 bool buf_valid(buf_T *buf)
   FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
   if (buf == NULL) {
     return false;
   }
-  FOR_ALL_BUFFERS(bp) {
+  // Assume that we more often have a recent buffer,
+  // start with the last one.
+  for (buf_T *bp = lastbuf; bp != NULL; bp = bp->b_prev) {
     if (bp == buf) {
       return true;
     }
@@ -363,13 +394,15 @@ void close_buffer(win_T *win, buf_T *buf, int action, int abort_if_last)
         win->w_cursor.col, TRUE);
   }
 
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+
   /* When the buffer is no longer in a window, trigger BufWinLeave */
   if (buf->b_nwindows == 1) {
     buf->b_closing = true;
-    apply_autocmds(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname,
-        FALSE, buf);
-    if (!buf_valid(buf)) {
-      /* Autocommands deleted the buffer. */
+    if (apply_autocmds(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname, false,
+                       buf) && !bufref_valid(&bufref)) {
+      // Autocommands deleted the buffer.
       EMSG(_(e_auabort));
       return;
     }
@@ -384,10 +417,9 @@ void close_buffer(win_T *win, buf_T *buf, int action, int abort_if_last)
      * BufHidden */
     if (!unload_buf) {
       buf->b_closing = true;
-      apply_autocmds(EVENT_BUFHIDDEN, buf->b_fname, buf->b_fname,
-          FALSE, buf);
-      if (!buf_valid(buf)) {
-        /* Autocommands deleted the buffer. */
+      if (apply_autocmds(EVENT_BUFHIDDEN, buf->b_fname, buf->b_fname, false,
+                         buf) && !bufref_valid(&bufref)) {
+        // Autocommands deleted the buffer.
         EMSG(_(e_auabort));
         return;
       }
@@ -431,11 +463,14 @@ void close_buffer(win_T *win, buf_T *buf, int action, int abort_if_last)
 
   buf_freeall(buf, (del_buf ? BFA_DEL : 0) + (wipe_buf ? BFA_WIPE : 0));
 
-  /* Autocommands may have deleted the buffer. */
-  if (!buf_valid(buf))
+  if (!bufref_valid(&bufref)) {
+    // Autocommands may have deleted the buffer.
     return;
-  if (aborting())           /* autocmds may abort script processing */
+  }
+  if (aborting()) {
+    // Autocmds may abort script processing.
     return;
+  }
 
   /*
    * It's possible that autocommands change curbuf to the one being deleted.
@@ -535,22 +570,29 @@ void buf_freeall(buf_T *buf, int flags)
 
   // Make sure the buffer isn't closed by autocommands.
   buf->b_closing = true;
-  if (buf->b_ml.ml_mfp != NULL) {
-      apply_autocmds(EVENT_BUFUNLOAD, buf->b_fname, buf->b_fname, false, buf);
-      if (!buf_valid(buf)) {    // autocommands may delete the buffer
-          return;
-      }
+
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+
+  if ((buf->b_ml.ml_mfp != NULL)
+      && apply_autocmds(EVENT_BUFUNLOAD, buf->b_fname, buf->b_fname, false, buf)
+      && !bufref_valid(&bufref)) {
+    // Autocommands deleted the buffer.
+    return;
   }
-  if ((flags & BFA_DEL) && buf->b_p_bl) {
-    apply_autocmds(EVENT_BUFDELETE, buf->b_fname, buf->b_fname, FALSE, buf);
-    if (!buf_valid(buf))            /* autocommands may delete the buffer */
-      return;
+  if ((flags & BFA_DEL)
+      && buf->b_p_bl
+      && apply_autocmds(EVENT_BUFDELETE, buf->b_fname, buf->b_fname, false, buf)
+      && !bufref_valid(&bufref)) {
+    // Autocommands may delete the buffer.
+    return;
   }
-  if (flags & BFA_WIPE) {
-    apply_autocmds(EVENT_BUFWIPEOUT, buf->b_fname, buf->b_fname,
-        FALSE, buf);
-    if (!buf_valid(buf))            /* autocommands may delete the buffer */
-      return;
+  if ((flags & BFA_WIPE)
+      && apply_autocmds(EVENT_BUFWIPEOUT, buf->b_fname, buf->b_fname, false,
+                        buf)
+      && !bufref_valid(&bufref)) {
+    // Autocommands may delete the buffer.
+    return;
   }
   buf->b_closing = false;
 
@@ -603,7 +645,8 @@ void buf_freeall(buf_T *buf, int flags)
 static void free_buffer(buf_T *buf)
 {
   handle_unregister_buffer(buf);
-  free_buffer_stuff(buf, TRUE);
+  buf_free_count++;
+  free_buffer_stuff(buf, true);
   unref_var_dict(buf->b_vars);
   aubuflocal_remove(buf);
   buf_hashtab_remove(buf);
@@ -678,8 +721,9 @@ static void clear_wininfo(buf_T *buf)
 void goto_buffer(exarg_T *eap, int start, int dir, int count)
 {
   (void)do_buffer(*eap->cmd == 's' ? DOBUF_SPLIT : DOBUF_GOTO,
-      start, dir, count, eap->forceit);
-  buf_T *old_curbuf = curbuf;
+                  start, dir, count, eap->forceit);
+  bufref_T old_curbuf;
+  set_bufref(&old_curbuf, curbuf);
   swap_exists_action = SEA_DIALOG;
 
   if (swap_exists_action == SEA_QUIT && *eap->cmd == 's') {
@@ -698,18 +742,20 @@ void goto_buffer(exarg_T *eap, int start, int dir, int count)
      * new aborting error, interrupt, or uncaught exception. */
     leave_cleanup(&cs);
   } else {
-    handle_swap_exists(old_curbuf);
+    handle_swap_exists(&old_curbuf);
   }
 }
 
-/*
- * Handle the situation of swap_exists_action being set.
- * It is allowed for "old_curbuf" to be NULL or invalid.
- */
-void handle_swap_exists(buf_T *old_curbuf)
+/// Handle the situation of swap_exists_action being set.
+///
+/// It is allowed for "old_curbuf" to be NULL or invalid.
+///
+/// @param old_curbuf The buffer to check for.
+void handle_swap_exists(bufref_T *old_curbuf)
 {
   cleanup_T cs;
   long old_tw = curbuf->b_p_tw;
+  buf_T *buf;
 
   if (swap_exists_action == SEA_QUIT) {
     /* Reset the error/interrupt/exception state here so that
@@ -722,13 +768,18 @@ void handle_swap_exists(buf_T *old_curbuf)
     swap_exists_action = SEA_NONE;      // don't want it again
     swap_exists_did_quit = true;
     close_buffer(curwin, curbuf, DOBUF_UNLOAD, false);
-    if (!buf_valid(old_curbuf) || old_curbuf == curbuf) {
-      old_curbuf = buflist_new(NULL, NULL, 1L, BLN_CURBUF | BLN_LISTED);
+    if (old_curbuf == NULL
+        || !bufref_valid(old_curbuf)
+        || old_curbuf->br_buf == curbuf) {
+      buf = buflist_new(NULL, NULL, 1L, BLN_CURBUF | BLN_LISTED);
+    } else {
+      buf = old_curbuf->br_buf;
     }
-    if (old_curbuf != NULL) {
-      enter_buffer(old_curbuf);
-      if (old_tw != curbuf->b_p_tw)
+    if (buf != NULL) {
+      enter_buffer(buf);
+      if (old_tw != curbuf->b_p_tw) {
         check_colorcolumn(curwin);
+      }
     }
     /* If "old_curbuf" is NULL we are in big trouble here... */
 
@@ -879,6 +930,9 @@ static int empty_curbuf(int close_others, int forceit, int action)
     return FAIL;
   }
 
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+
   if (close_others) {
     /* Close any other windows on this buffer, then make it empty. */
     close_windows(buf, TRUE);
@@ -888,15 +942,17 @@ static int empty_curbuf(int close_others, int forceit, int action)
   retval = do_ecmd(0, NULL, NULL, NULL, ECMD_ONE,
       forceit ? ECMD_FORCEIT : 0, curwin);
 
-  /*
-   * do_ecmd() may create a new buffer, then we have to delete
-   * the old one.  But do_ecmd() may have done that already, check
-   * if the buffer still exists.
-   */
-  if (buf != curbuf && buf_valid(buf) && buf->b_nwindows == 0)
-    close_buffer(NULL, buf, action, FALSE);
-  if (!close_others)
-    need_fileinfo = FALSE;
+  // do_ecmd() may create a new buffer, then we have to delete
+  // the old one.  But do_ecmd() may have done that already, check
+  // if the buffer still exists.
+  if (buf != curbuf && bufref_valid(&bufref) && buf->b_nwindows == 0) {
+    close_buffer(NULL, buf, action, false);
+  }
+
+  if (!close_others) {
+    need_fileinfo = false;
+  }
+
   return retval;
 }
 /*
@@ -998,6 +1054,8 @@ do_buffer (
    */
   if (unload) {
     int forward;
+    bufref_T bufref;
+    set_bufref(&bufref, buf);
 
     /* When unloading or deleting a buffer that's already unloaded and
      * unlisted: fail silently. */
@@ -1006,15 +1064,16 @@ do_buffer (
 
     if (!forceit && (buf->terminal || bufIsChanged(buf))) {
       if ((p_confirm || cmdmod.confirm) && p_write && !buf->terminal) {
-        dialog_changed(buf, FALSE);
-        if (!buf_valid(buf))
-          /* Autocommand deleted buffer, oops!  It's not changed
-           * now. */
+        dialog_changed(buf, false);
+        if (!bufref_valid(&bufref)) {
+          // Autocommand deleted buffer, oops! It's not changed now.
           return FAIL;
-        /* If it's still changed fail silently, the dialog already
-         * mentioned why it fails. */
-        if (bufIsChanged(buf))
+        }
+        // If it's still changed fail silently, the dialog already
+        // mentioned why it fails.
+        if (bufIsChanged(buf)) {
           return FAIL;
+        }
       } else {
         if (buf->terminal) {
           EMSG2(_("E89: %s will be killed(add ! to override)"),
@@ -1058,27 +1117,26 @@ do_buffer (
      * If the buffer to be deleted is not the current one, delete it here.
      */
     if (buf != curbuf) {
-      close_windows(buf, FALSE);
-      if (buf != curbuf && buf_valid(buf) && buf->b_nwindows <= 0)
-        close_buffer(NULL, buf, action, FALSE);
+      close_windows(buf, false);
+      if (buf != curbuf && bufref_valid(&bufref) && buf->b_nwindows <= 0) {
+        close_buffer(NULL, buf, action, false);
+      }
       return OK;
     }
 
-    /*
-     * Deleting the current buffer: Need to find another buffer to go to.
-     * There should be another, otherwise it would have been handled
-     * above.  However, autocommands may have deleted all buffers.
-     * First use au_new_curbuf, if it is valid.
-     * Then prefer the buffer we most recently visited.
-     * Else try to find one that is loaded, after the current buffer,
-     * then before the current buffer.
-     * Finally use any buffer.
-     */
-    buf = NULL;         /* selected buffer */
-    bp = NULL;          /* used when no loaded buffer found */
-    if (au_new_curbuf != NULL && buf_valid(au_new_curbuf))
-      buf = au_new_curbuf;
-    else if (curwin->w_jumplistlen > 0) {
+    // Deleting the current buffer: Need to find another buffer to go to.
+    // There should be another, otherwise it would have been handled
+    // above.  However, autocommands may have deleted all buffers.
+    // First use au_new_curbuf.br_buf, if it is valid.
+    // Then prefer the buffer we most recently visited.
+    // Else try to find one that is loaded, after the current buffer,
+    // then before the current buffer.
+    // Finally use any buffer.
+    buf = NULL;  // Selected buffer.
+    bp = NULL;   // Used when no loaded buffer found.
+    if (au_new_curbuf.br_buf != NULL && bufref_valid(&au_new_curbuf)) {
+      buf = au_new_curbuf.br_buf;
+    } else if (curwin->w_jumplistlen > 0) {
       int jumpidx;
 
       jumpidx = curwin->w_jumplistidx - 1;
@@ -1183,10 +1241,13 @@ do_buffer (
    */
   if (action == DOBUF_GOTO && !can_abandon(curbuf, forceit)) {
     if ((p_confirm || cmdmod.confirm) && p_write) {
-      dialog_changed(curbuf, FALSE);
-      if (!buf_valid(buf))
-        /* Autocommand deleted buffer, oops! */
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
+      dialog_changed(curbuf, false);
+      if (!bufref_valid(&bufref)) {
+        // Autocommand deleted buffer, oops!
         return FAIL;
+      }
     }
     if (bufIsChanged(curbuf)) {
       EMSG(_(e_nowrtmsg));
@@ -1234,14 +1295,18 @@ void set_curbuf(buf_T *buf, int action)
 
   /* close_windows() or apply_autocmds() may change curbuf */
   prevbuf = curbuf;
+  bufref_T bufref;
+  set_bufref(&bufref, prevbuf);
 
-  apply_autocmds(EVENT_BUFLEAVE, NULL, NULL, FALSE, curbuf);
-  if (buf_valid(prevbuf) && !aborting()) {
-    if (prevbuf == curwin->w_buffer)
+  if (!apply_autocmds(EVENT_BUFLEAVE, NULL, NULL, false, curbuf)
+      || (bufref_valid(&bufref) && !aborting())) {
+    if (prevbuf == curwin->w_buffer) {
       reset_synblock(curwin);
-    if (unload)
-      close_windows(prevbuf, FALSE);
-    if (buf_valid(prevbuf) && !aborting()) {
+    }
+    if (unload) {
+      close_windows(prevbuf, false);
+    }
+    if (bufref_valid(&bufref) && !aborting()) {
       win_T  *previouswin = curwin;
       if (prevbuf == curbuf)
         u_sync(FALSE);
@@ -1378,6 +1443,8 @@ static int top_file_num = 1;            ///< highest file number
 /// If (flags & BLN_LISTED) is TRUE, add new buffer to buffer list.
 /// If (flags & BLN_DUMMY) is TRUE, don't count it as a real buffer.
 /// If (flags & BLN_NEW) is TRUE, don't use an existing buffer.
+/// If (flags & BLN_NOOPT) is TRUE, don't copy options from the current buffer
+///                                 if the buffer already exists.
 /// This is the ONLY way to create a new buffer.
 ///
 /// @param ffname full path of fname or relative
@@ -1408,16 +1475,20 @@ buf_T * buflist_new(char_u *ffname, char_u *sfname, linenr_T lnum, int flags)
       && (buf = buflist_findname_file_id(ffname, &file_id,
                                          file_id_valid)) != NULL) {
     xfree(ffname);
-    if (lnum != 0)
-      buflist_setfpos(buf, curwin, lnum, (colnr_T)0, FALSE);
-    /* copy the options now, if 'cpo' doesn't have 's' and not done
-     * already */
-    buf_copy_options(buf, 0);
+    if (lnum != 0) {
+      buflist_setfpos(buf, curwin, lnum, (colnr_T)0, false);
+    }
+    if ((flags & BLN_NOOPT) == 0) {
+      // Copy the options now, if 'cpo' doesn't have 's' and not done already.
+      buf_copy_options(buf, 0);
+    }
     if ((flags & BLN_LISTED) && !buf->b_p_bl) {
-      buf->b_p_bl = TRUE;
+      buf->b_p_bl = true;
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
       if (!(flags & BLN_DUMMY)) {
-        apply_autocmds(EVENT_BUFADD, NULL, NULL, FALSE, buf);
-        if (!buf_valid(buf)) {
+        if (apply_autocmds(EVENT_BUFADD, NULL, NULL, false, buf)
+            && !bufref_valid(&bufref)) {
           return NULL;
         }
       }
@@ -1551,18 +1622,21 @@ buf_T * buflist_new(char_u *ffname, char_u *sfname, linenr_T lnum, int flags)
     // Tricky: these autocommands may change the buffer list.  They could also
     // split the window with re-using the one empty buffer. This may result in
     // unexpectedly losing the empty buffer.
-    apply_autocmds(EVENT_BUFNEW, NULL, NULL, FALSE, buf);
-    if (!buf_valid(buf)) {
+    bufref_T bufref;
+    set_bufref(&bufref, buf);
+    if (apply_autocmds(EVENT_BUFNEW, NULL, NULL, false, buf)
+        && !bufref_valid(&bufref)) {
       return NULL;
     }
-    if (flags & BLN_LISTED) {
-      apply_autocmds(EVENT_BUFADD, NULL, NULL, FALSE, buf);
-      if (!buf_valid(buf)) {
-        return NULL;
-      }
+    if ((flags & BLN_LISTED)
+        && apply_autocmds(EVENT_BUFADD, NULL, NULL, false, buf)
+        && !bufref_valid(&bufref)) {
+      return NULL;
     }
-    if (aborting())             /* autocmds may abort script processing */
+    if (aborting()) {
+      // Autocmds may abort script processing.
       return NULL;
+    }
   }
 
   return buf;
@@ -1785,7 +1859,8 @@ buf_T *buflist_findname(char_u *ffname)
 static buf_T *buflist_findname_file_id(char_u *ffname, FileID *file_id,
                                        bool file_id_valid)
 {
-  FOR_ALL_BUFFERS(buf) {
+  // Start at the last buffer, expect to find a match sooner.
+  FOR_ALL_BUFFERS_BACKWARDS(buf) {
     if ((buf->b_flags & BF_DUMMY) == 0
         && !otherfile_buf(buf, ffname, file_id, file_id_valid)) {
       return buf;
@@ -1859,7 +1934,7 @@ int buflist_findpat(
           return -1;
         }
 
-        FOR_ALL_BUFFERS(buf) {
+        FOR_ALL_BUFFERS_BACKWARDS(buf) {
           if (buf->b_p_bl == find_listed
               && (!diffmode || diff_mode_buf(buf))
               && buflist_match(&regmatch, buf, false) != NULL) {
@@ -4223,12 +4298,13 @@ do_arg_all (
             || !bufIsChanged(buf)) {
           /* If the buffer was changed, and we would like to hide it,
            * try autowriting. */
-          if (!P_HID(buf) && buf->b_nwindows <= 1
-              && bufIsChanged(buf)) {
-            (void)autowrite(buf, FALSE);
-            /* check if autocommands removed the window */
-            if (!win_valid(wp) || !buf_valid(buf)) {
-              wpnext = firstwin;                /* start all over... */
+          if (!P_HID(buf) && buf->b_nwindows <= 1 && bufIsChanged(buf)) {
+            bufref_T bufref;
+            set_bufref(&bufref, buf);
+            (void)autowrite(buf, false);
+            // Check if autocommands removed the window.
+            if (!win_valid(wp) || !bufref_valid(&bufref)) {
+              wpnext = firstwin;  // Start all over...
               continue;
             }
           }
@@ -4442,7 +4518,9 @@ void ex_buffer_all(exarg_T *eap)
     }
 
     if (wp == NULL && split_ret == OK) {
-      /* Split the window and put the buffer in it */
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
+      // Split the window and put the buffer in it.
       p_ea_save = p_ea;
       p_ea = true;                      /* use space from all windows */
       split_ret = win_split(0, WSP_ROOM | WSP_BELOW);
@@ -4454,7 +4532,8 @@ void ex_buffer_all(exarg_T *eap)
       /* Open the buffer in this window. */
       swap_exists_action = SEA_DIALOG;
       set_curbuf(buf, DOBUF_GOTO);
-      if (!buf_valid(buf)) {            /* autocommands deleted the buffer!!! */
+      if (!bufref_valid(&bufref)) {
+        // Autocommands deleted the buffer.
         swap_exists_action = SEA_NONE;
         break;
       }
diff --git a/src/nvim/buffer.h b/src/nvim/buffer.h
index 36cbec7e60..193c9f73d8 100644
--- a/src/nvim/buffer.h
+++ b/src/nvim/buffer.h
@@ -15,9 +15,11 @@ enum getf_values {
 
 // Values for buflist_new() flags
 enum bln_values {
-  BLN_CURBUF = 1, // May re-use curbuf for new buffer
-  BLN_LISTED = 2, // Put new buffer in buffer list
-  BLN_DUMMY  = 4, // Allocating dummy buffer
+  BLN_CURBUF = 1,   // May re-use curbuf for new buffer
+  BLN_LISTED = 2,   // Put new buffer in buffer list
+  BLN_DUMMY  = 4,   // Allocating dummy buffer
+  // TODO(mhinz): merge patch that introduces BLN_NEW
+  BLN_NOOPT  = 16,  // Don't copy options to existing buffer
 };
 
 // Values for action argument for do_buffer()
@@ -55,21 +57,22 @@ enum bfa_values {
 static inline void switch_to_win_for_buf(buf_T *buf,
                                          win_T **save_curwinp,
                                          tabpage_T **save_curtabp,
-                                         buf_T **save_curbufp)
+                                         bufref_T *save_curbuf)
 {
   win_T *wp;
   tabpage_T *tp;
 
   if (!find_win_for_buf(buf, &wp, &tp)
-      || switch_win(save_curwinp, save_curtabp, wp, tp, true) == FAIL)
-    switch_buffer(save_curbufp, buf);
+      || switch_win(save_curwinp, save_curtabp, wp, tp, true) == FAIL) {
+    switch_buffer(save_curbuf, buf);
+  }
 }
 
 static inline void restore_win_for_buf(win_T *save_curwin,
                                        tabpage_T *save_curtab,
-                                       buf_T *save_curbuf)
+                                       bufref_T *save_curbuf)
 {
-  if (save_curbuf == NULL) {
+  if (save_curbuf->br_buf == NULL) {
     restore_win(save_curwin, save_curtab, true);
   } else {
     restore_buffer(save_curbuf);
@@ -78,12 +81,12 @@ static inline void restore_win_for_buf(win_T *save_curwin,
 
 #define WITH_BUFFER(b, code) \
   do { \
-    buf_T *save_curbuf = NULL; \
     win_T *save_curwin = NULL; \
     tabpage_T *save_curtab = NULL; \
+    bufref_T save_curbuf = { NULL, 0 }; \
     switch_to_win_for_buf(b, &save_curwin, &save_curtab, &save_curbuf); \
     code; \
-    restore_win_for_buf(save_curwin, save_curtab, save_curbuf); \
+    restore_win_for_buf(save_curwin, save_curtab, &save_curbuf); \
   } while (0)
 
 
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 29f4dfe4fb..73d06de964 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -8,6 +8,13 @@
 
 typedef struct file_buffer buf_T; // Forward declaration
 
+// Reference to a buffer that stores the value of buf_free_count.
+// bufref_valid() only needs to check "buf" when the count differs.
+typedef struct {
+  buf_T *br_buf;
+  int    br_buf_free_count;
+} bufref_T;
+
 // for garray_T
 #include "nvim/garray.h"
 // for pos_T, lpos_T and linenr_T
diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index f7b96ba3e1..aafd50687e 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -1004,7 +1004,8 @@ theend:
 void ex_diffsplit(exarg_T *eap)
 {
   win_T *old_curwin = curwin;
-  buf_T *old_curbuf = curbuf;
+  bufref_T old_curbuf;
+  set_bufref(&old_curbuf, curbuf);
 
   // don't use a new tab page, each tab page has its own diffs
   cmdmod.tab = 0;
@@ -1022,10 +1023,10 @@ void ex_diffsplit(exarg_T *eap)
       if (win_valid(old_curwin)) {
         diff_win_options(old_curwin, true);
 
-        if (buf_valid(old_curbuf)) {
+        if (bufref_valid(&old_curbuf)) {
           // Move the cursor position to that of the old window.
           curwin->w_cursor.lnum = diff_get_corresponding_line(
-              old_curbuf,
+              old_curbuf.br_buf,
               old_curwin->w_cursor.lnum,
               curbuf,
               curwin->w_cursor.lnum);
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 2ec04eee0b..1cc84f8c16 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -10306,7 +10306,7 @@ static void f_getcompletion(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   ExpandInit(&xpc);
   xpc.xp_pattern = get_tv_string(&argvars[0]);
-  xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+  xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
   xpc.xp_context = cmdcomplete_str_to_type(get_tv_string(&argvars[1]));
   if (xpc.xp_context == EXPAND_NOTHING) {
     if (argvars[1].v_type == VAR_STRING) {
@@ -10319,17 +10319,17 @@ static void f_getcompletion(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 
   if (xpc.xp_context == EXPAND_MENUS) {
     set_context_in_menu_cmd(&xpc, (char_u *)"menu", xpc.xp_pattern, false);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
   }
 
   if (xpc.xp_context == EXPAND_CSCOPE) {
     set_context_in_cscope_cmd(&xpc, xpc.xp_pattern, CMD_cscope);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
   }
 
   if (xpc.xp_context == EXPAND_SIGN) {
     set_context_in_sign_cmd(&xpc, xpc.xp_pattern);
-    xpc.xp_pattern_len = STRLEN(xpc.xp_pattern);
+    xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
   }
 
   pat = addstar(xpc.xp_pattern, xpc.xp_pattern_len, xpc.xp_context);
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index e6e85a3f6c..3b7f3b7b97 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -1904,11 +1904,15 @@ void do_wqall(exarg_T *eap)
                    FALSE) == FAIL) {
       ++error;
     } else {
-      if (buf_write_all(buf, eap->forceit) == FAIL)
-        ++error;
-      /* an autocommand may have deleted the buffer */
-      if (!buf_valid(buf))
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
+      if (buf_write_all(buf, eap->forceit) == FAIL) {
+        error++;
+      }
+      // An autocommand may have deleted the buffer.
+      if (!bufref_valid(&bufref)) {
         buf = firstbuf;
+      }
     }
     eap->forceit = save_forceit;          /* check_overwrite() may set it */
   }
@@ -2081,7 +2085,8 @@ int do_ecmd(
   char_u      *new_name = NULL;
   int did_set_swapcommand = FALSE;
   buf_T       *buf;
-  buf_T       *old_curbuf = curbuf;
+  bufref_T     bufref;
+  bufref_T     old_curbuf;
   char_u      *free_fname = NULL;
   int retval = FAIL;
   long n;
@@ -2098,6 +2103,8 @@ int do_ecmd(
   if (eap != NULL)
     command = eap->do_ecmd_cmd;
 
+  set_bufref(&old_curbuf, curbuf);
+
   if (fnum != 0) {
     if (fnum == curbuf->b_fnum)         /* file is already being edited */
       return OK;                        /* nothing to do */
@@ -2209,23 +2216,27 @@ int do_ecmd(
       if (oldwin != NULL) {
         oldwin = curwin;
       }
-      old_curbuf = curbuf;
+      set_bufref(&old_curbuf, curbuf);
     }
     if (buf == NULL)
       goto theend;
-    if (buf->b_ml.ml_mfp == NULL) {             /* no memfile yet */
-      oldbuf = FALSE;
-    } else {                                  /* existing memfile */
-      oldbuf = TRUE;
-      (void)buf_check_timestamp(buf, FALSE);
-      /* Check if autocommands made buffer invalid or changed the current
-       * buffer. */
-      if (!buf_valid(buf)
-          || curbuf != old_curbuf
-          )
+    if (buf->b_ml.ml_mfp == NULL) {
+      // No memfile yet.
+      oldbuf = false;
+    } else {
+      // Existing memfile.
+      oldbuf = true;
+      set_bufref(&bufref, buf);
+      (void)buf_check_timestamp(buf, false);
+      // Check if autocommands made buffer invalid or changed the current
+      // buffer.
+      if (!bufref_valid(&bufref) || curbuf != old_curbuf.br_buf) {
         goto theend;
-      if (aborting())               /* autocmds may abort script processing */
+      }
+      if (aborting()) {
+        // Autocmds may abort script processing.
         goto theend;
+      }
     }
 
     /* May jump to last used line number for a loaded buffer or when asked
@@ -2253,12 +2264,14 @@ int do_ecmd(
        * - If we ended up in the new buffer already, need to skip a few
        *	 things, set auto_buf.
        */
-      if (buf->b_fname != NULL)
+      if (buf->b_fname != NULL) {
         new_name = vim_strsave(buf->b_fname);
-      au_new_curbuf = buf;
-      apply_autocmds(EVENT_BUFLEAVE, NULL, NULL, FALSE, curbuf);
-      if (!buf_valid(buf)) {            /* new buffer has been deleted */
-        delbuf_msg(new_name);           /* frees new_name */
+      }
+      set_bufref(&au_new_curbuf, buf);
+      apply_autocmds(EVENT_BUFLEAVE, NULL, NULL, false, curbuf);
+      if (!bufref_valid(&au_new_curbuf)) {
+        // New buffer has been deleted.
+        delbuf_msg(new_name);  // Frees new_name.
         goto theend;
       }
       if (aborting()) {             /* autocmds may abort script processing */
@@ -2272,7 +2285,7 @@ int do_ecmd(
 
         // Set the w_closing flag to avoid that autocommands close the window.
         the_curwin->w_closing = true;
-        if (curbuf == old_curbuf) {
+        if (curbuf == old_curbuf.br_buf) {
           buf_copy_options(buf, BCO_ENTER);
         }
 
@@ -2290,9 +2303,10 @@ int do_ecmd(
           xfree(new_name);
           goto theend;
         }
-        /* Be careful again, like above. */
-        if (!buf_valid(buf)) {          /* new buffer has been deleted */
-          delbuf_msg(new_name);                 /* frees new_name */
+        // Be careful again, like above.
+        if (!bufref_valid(&au_new_curbuf)) {
+          // New buffer has been deleted.
+          delbuf_msg(new_name);  // Frees new_name.
           goto theend;
         }
         if (buf == curbuf) {  // already in new buffer
@@ -2325,7 +2339,7 @@ int do_ecmd(
 
       }
       xfree(new_name);
-      au_new_curbuf = NULL;
+      au_new_curbuf.br_buf = NULL;
     }
 
     curwin->w_pcmark.lnum = 1;
@@ -2378,10 +2392,12 @@ int do_ecmd(
       solcol = curwin->w_cursor.col;
     }
     buf = curbuf;
-    if (buf->b_fname != NULL)
+    if (buf->b_fname != NULL) {
       new_name = vim_strsave(buf->b_fname);
-    else
+    } else {
       new_name = NULL;
+    }
+    set_bufref(&bufref, buf);
     if (p_ur < 0 || curbuf->b_ml.ml_line_count <= p_ur) {
       /* Save all the text, so that the reload can be undone.
        * Sync first so that this is a separate undo-able action. */
@@ -2394,14 +2410,15 @@ int do_ecmd(
       u_unchanged(curbuf);
       buf_freeall(curbuf, BFA_KEEP_UNDO);
 
-      /* tell readfile() not to clear or reload undo info */
+      // Tell readfile() not to clear or reload undo info.
       readfile_flags = READ_KEEP_UNDO;
-    } else
-      buf_freeall(curbuf, 0);         /* free all things for buffer */
-    /* If autocommands deleted the buffer we were going to re-edit, give
-     * up and jump to the end. */
-    if (!buf_valid(buf)) {
-      delbuf_msg(new_name);             /* frees new_name */
+    } else {
+      buf_freeall(curbuf, 0);  // Free all things for buffer.
+    }
+    // If autocommands deleted the buffer we were going to re-edit, give
+    // up and jump to the end.
+    if (!bufref_valid(&bufref)) {
+      delbuf_msg(new_name);  // Frees new_name.
       goto theend;
     }
     xfree(new_name);
@@ -2472,7 +2489,7 @@ int do_ecmd(
 
       if (swap_exists_action == SEA_QUIT)
         retval = FAIL;
-      handle_swap_exists(old_curbuf);
+      handle_swap_exists(&old_curbuf);
     } else {
       /* Read the modelines, but only to set window-local options.  Any
        * buffer-local options have already been set and may have been
@@ -2607,7 +2624,7 @@ static void delbuf_msg(char_u *name)
   EMSG2(_("E143: Autocommands unexpectedly deleted new buffer %s"),
       name == NULL ? (char_u *)"" : name);
   xfree(name);
-  au_new_curbuf = NULL;
+  au_new_curbuf.br_buf = NULL;
 }
 
 static int append_indent = 0;       /* autoindent for first line */
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 3b92b3734a..b4e57bc916 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -1181,6 +1181,7 @@ bool prof_def_func(void)
 int autowrite(buf_T *buf, int forceit)
 {
   int r;
+  bufref_T bufref;
 
   if (!(p_aw || p_awa) || !p_write
       // never autowrite a "nofile" or "nowrite" buffer
@@ -1188,11 +1189,12 @@ int autowrite(buf_T *buf, int forceit)
       || (!forceit && buf->b_p_ro) || buf->b_ffname == NULL) {
     return FAIL;
   }
+  set_bufref(&bufref, buf);
   r = buf_write_all(buf, forceit);
 
   // Writing may succeed but the buffer still changed, e.g., when there is a
   // conversion error.  We do want to return FAIL then.
-  if (buf_valid(buf) && bufIsChanged(buf)) {
+  if (bufref_valid(&bufref) && bufIsChanged(buf)) {
     r = FAIL;
   }
   return r;
@@ -1207,9 +1209,11 @@ void autowrite_all(void)
 
   FOR_ALL_BUFFERS(buf) {
     if (bufIsChanged(buf) && !buf->b_p_ro) {
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
       (void)buf_write_all(buf, false);
       // an autocommand may have deleted the buffer
-      if (!buf_valid(buf)) {
+      if (!bufref_valid(&bufref)) {
         buf = firstbuf;
       }
     }
@@ -1221,6 +1225,8 @@ void autowrite_all(void)
 bool check_changed(buf_T *buf, int flags)
 {
   int forceit = (flags & CCGD_FORCEIT);
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
 
   if (!forceit
       && bufIsChanged(buf)
@@ -1236,12 +1242,12 @@ bool check_changed(buf_T *buf, int flags)
           }
         }
       }
-      if (!buf_valid(buf)) {
+      if (!bufref_valid(&bufref)) {
         // Autocommand deleted buffer, oops!  It's not changed now.
         return false;
       }
       dialog_changed(buf, count > 1);
-      if (!buf_valid(buf)) {
+      if (!bufref_valid(&bufref)) {
         // Autocommand deleted buffer, oops!  It's not changed now.
         return false;
       }
@@ -1300,9 +1306,10 @@ void dialog_changed(buf_T *buf, int checkall)
     // Skip readonly buffers, these need to be confirmed
     // individually.
     FOR_ALL_BUFFERS(buf2) {
-      if (bufIsChanged(buf2)
-          && (buf2->b_ffname != NULL)
-          && !buf2->b_p_ro) {
+      if (bufIsChanged(buf2) && (buf2->b_ffname != NULL) && !buf2->b_p_ro) {
+        bufref_T bufref;
+        set_bufref(&bufref, buf2);
+
         if (buf2->b_fname != NULL
             && check_overwrite(&ea, buf2, buf2->b_fname,
                                buf2->b_ffname, false) == OK) {
@@ -1310,7 +1317,7 @@ void dialog_changed(buf_T *buf, int checkall)
           (void)buf_write_all(buf2, false);
         }
         // an autocommand may have deleted the buffer
-        if (!buf_valid(buf2)) {
+        if (!bufref_valid(&bufref)) {
           buf2 = firstbuf;
         }
       }
@@ -1407,11 +1414,14 @@ bool check_changed_any(bool hidden, bool unload)
       continue;
     }
     if ((!hidden || buf->b_nwindows == 0) && bufIsChanged(buf)) {
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
+
       // Try auto-writing the buffer.  If this fails but the buffer no
       // longer exists it's not changed, that's OK.
       if (check_changed(buf, (p_awa ? CCGD_AW : 0)
                         | CCGD_MULTWIN
-                        | CCGD_ALLBUF) && buf_valid(buf)) {
+                        | CCGD_ALLBUF) && bufref_valid(&bufref)) {
         break;    // didn't save - still changes
       }
     }
@@ -1447,9 +1457,11 @@ bool check_changed_any(bool hidden, bool unload)
   if (buf != curbuf) {
     FOR_ALL_TAB_WINDOWS(tp, wp) {
       if (wp->w_buffer == buf) {
+        bufref_T bufref;
+        set_bufref(&bufref, buf);
         goto_tabpage_win(tp, wp);
         // Paranoia: did autocmds wipe out the buffer with changes?
-        if (!buf_valid(buf)) {
+        if (!bufref_valid(&bufref)) {
           goto theend;
         }
         goto buf_found;
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 4070e9fe5b..c5625d7882 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5914,10 +5914,13 @@ ex_win_close (
   need_hide = (bufIsChanged(buf) && buf->b_nwindows <= 1);
   if (need_hide && !P_HID(buf) && !forceit) {
     if ((p_confirm || cmdmod.confirm) && p_write) {
-      dialog_changed(buf, FALSE);
-      if (buf_valid(buf) && bufIsChanged(buf))
+      bufref_T bufref;
+      set_bufref(&bufref, buf);
+      dialog_changed(buf, false);
+      if (bufref_valid(&bufref) && bufIsChanged(buf)) {
         return;
-      need_hide = FALSE;
+      }
+      need_hide = false;
     } else {
       EMSG(_(e_nowrtmsg));
       return;
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index dba7a73814..2555b64dfd 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -5134,9 +5134,9 @@ int cmd_gchar(int offset)
 static int ex_window(void)
 {
   struct cmdline_info save_ccline;
-  buf_T               *old_curbuf = curbuf;
+  bufref_T            old_curbuf;
+  bufref_T            bufref;
   win_T               *old_curwin = curwin;
-  buf_T               *bp;
   win_T               *wp;
   int i;
   linenr_T lnum;
@@ -5155,6 +5155,8 @@ static int ex_window(void)
     return K_IGNORE;
   }
 
+  set_bufref(&old_curbuf, curbuf);
+
   /* Save current window sizes. */
   win_size_save(&winsizes);
 
@@ -5269,7 +5271,7 @@ static int ex_window(void)
 
   /* Safety check: The old window or buffer was deleted: It's a bug when
    * this happens! */
-  if (!win_valid(old_curwin) || !buf_valid(old_curbuf)) {
+  if (!win_valid(old_curwin) || !bufref_valid(&old_curbuf)) {
     cmdwin_result = Ctrl_C;
     EMSG(_("E199: Active window or buffer deleted"));
   } else {
@@ -5320,14 +5322,15 @@ static int ex_window(void)
     // Avoid command-line window first character being concealed
     curwin->w_p_cole = 0;
     wp = curwin;
-    bp = curbuf;
+    set_bufref(&bufref, curbuf);
     win_goto(old_curwin);
     win_close(wp, TRUE);
 
-    /* win_close() may have already wiped the buffer when 'bh' is
-     * set to 'wipe' */
-    if (buf_valid(bp))
-      close_buffer(NULL, bp, DOBUF_WIPE, FALSE);
+    // win_close() may have already wiped the buffer when 'bh' is
+    // set to 'wipe'.
+    if (bufref_valid(&bufref)) {
+      close_buffer(NULL, bufref.br_buf, DOBUF_WIPE, false);
+    }
 
     /* Restore window sizes. */
     win_size_restore(&winsizes);
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index d433afab3e..cdb912ca94 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -2402,6 +2402,7 @@ buf_write (
     int did_cmd = FALSE;
     int nofile_err = FALSE;
     int empty_memline = (buf->b_ml.ml_mfp == NULL);
+    bufref_T bufref;
 
     /*
      * Apply PRE autocommands.
@@ -2417,8 +2418,9 @@ buf_write (
     if (fname == buf->b_sfname)
       buf_fname_s = TRUE;
 
-    /* set curwin/curbuf to buf and save a few things */
+    // Set curwin/curbuf to buf and save a few things.
     aucmd_prepbuf(&aco, buf);
+    set_bufref(&bufref, buf);
 
     if (append) {
       if (!(did_cmd = apply_autocmds_exarg(EVENT_FILEAPPENDCMD,
@@ -2466,14 +2468,13 @@ buf_write (
     /* restore curwin/curbuf and a few other things */
     aucmd_restbuf(&aco);
 
-    /*
-     * In three situations we return here and don't write the file:
-     * 1. the autocommands deleted or unloaded the buffer.
-     * 2. The autocommands abort script processing.
-     * 3. If one of the "Cmd" autocommands was executed.
-     */
-    if (!buf_valid(buf))
+    // In three situations we return here and don't write the file:
+    // 1. the autocommands deleted or unloaded the buffer.
+    // 2. The autocommands abort script processing.
+    // 3. If one of the "Cmd" autocommands was executed.
+    if (!bufref_valid(&bufref)) {
       buf = NULL;
+    }
     if (buf == NULL || (buf->b_ml.ml_mfp == NULL && !empty_memline)
         || did_cmd || nofile_err
         || aborting()
@@ -4760,12 +4761,14 @@ check_timestamps (
     for (buf = firstbuf; buf != NULL; ) {
       /* Only check buffers in a window. */
       if (buf->b_nwindows > 0) {
+        bufref_T bufref;
+        set_bufref(&bufref, buf);
         n = buf_check_timestamp(buf, focus);
-        if (didit < n)
+        if (didit < n) {
           didit = n;
-        if (n > 0 && !buf_valid(buf)) {
-          /* Autocommands have removed the buffer, start at the
-           * first one again. */
+        }
+        if (n > 0 && !bufref_valid(&bufref)) {
+          // Autocommands have removed the buffer, start at the first one again.
           buf = firstbuf;
           continue;
         }
@@ -4850,6 +4853,9 @@ buf_check_timestamp (
   char_u      *s;
   char        *reason;
 
+  bufref_T bufref;
+  set_bufref(&bufref, buf);
+
   // If its a terminal, there is no file name, the buffer is not loaded,
   // 'buftype' is set, we are in the middle of a save or being called
   // recursively: ignore this buffer.
@@ -4919,8 +4925,9 @@ buf_check_timestamp (
       allbuf_lock--;
       busy = false;
       if (n) {
-        if (!buf_valid(buf))
+        if (!bufref_valid(&bufref)) {
           EMSG(_("E246: FileChangedShell autocommand deleted buffer"));
+        }
         s = get_vim_var_str(VV_FCS_CHOICE);
         if (STRCMP(s, "reload") == 0 && *reason != 'd')
           reload = TRUE;
@@ -5037,11 +5044,11 @@ buf_check_timestamp (
     }
   }
 
-  /* Trigger FileChangedShell when the file was changed in any way. */
-  if (buf_valid(buf) && retval != 0)
-    (void)apply_autocmds(EVENT_FILECHANGEDSHELLPOST,
-        buf->b_fname, buf->b_fname, FALSE, buf);
-
+  // Trigger FileChangedShell when the file was changed in any way.
+  if (bufref_valid(&bufref) && retval != 0) {
+    (void)apply_autocmds(EVENT_FILECHANGEDSHELLPOST, buf->b_fname, buf->b_fname,
+                         false, buf);
+  }
   return retval;
 }
 
@@ -5058,6 +5065,7 @@ void buf_reload(buf_T *buf, int orig_mode)
   linenr_T old_topline;
   int old_ro = buf->b_p_ro;
   buf_T       *savebuf;
+  bufref_T bufref;
   int saved = OK;
   aco_save_T aco;
   int flags = READ_NEW;
@@ -5093,6 +5101,7 @@ void buf_reload(buf_T *buf, int orig_mode)
   } else {
     // Allocate a buffer without putting it in the buffer list.
     savebuf = buflist_new(NULL, NULL, (linenr_T)1, BLN_DUMMY);
+    set_bufref(&bufref, savebuf);
     if (savebuf != NULL && buf == curbuf) {
       /* Open the memline. */
       curbuf = savebuf;
@@ -5117,12 +5126,14 @@ void buf_reload(buf_T *buf, int orig_mode)
       if (!aborting()) {
         EMSG2(_("E321: Could not reload \"%s\""), buf->b_fname);
       }
-      if (savebuf != NULL && buf_valid(savebuf) && buf == curbuf) {
-        /* Put the text back from the save buffer.  First
-         * delete any lines that readfile() added. */
-        while (!bufempty())
-          if (ml_delete(buf->b_ml.ml_line_count, FALSE) == FAIL)
+      if (savebuf != NULL && bufref_valid(&bufref) && buf == curbuf) {
+        // Put the text back from the save buffer.  First
+        // delete any lines that readfile() added.
+        while (!bufempty()) {
+          if (ml_delete(buf->b_ml.ml_line_count, false) == FAIL) {
             break;
+          }
+        }
         (void)move_lines(savebuf, buf);
       }
     } else if (buf == curbuf) {  /* "buf" still valid */
@@ -5139,8 +5150,9 @@ void buf_reload(buf_T *buf, int orig_mode)
   }
   xfree(ea.cmd);
 
-  if (savebuf != NULL && buf_valid(savebuf))
-    wipe_buffer(savebuf, FALSE);
+  if (savebuf != NULL && bufref_valid(&bufref)) {
+    wipe_buffer(savebuf, false);
+  }
 
   /* Invalidate diff info if necessary. */
   diff_invalidate(curbuf);
@@ -6288,6 +6300,7 @@ void ex_doautoall(exarg_T *eap)
   aco_save_T aco;
   char_u      *arg = eap->arg;
   int call_do_modelines = check_nomodeline(&arg);
+  bufref_T bufref;
 
   /*
    * This is a bit tricky: For some commands curwin->w_buffer needs to be
@@ -6300,8 +6313,9 @@ void ex_doautoall(exarg_T *eap)
     if (buf->b_ml.ml_mfp == NULL) {
       continue;
     }
-    /* find a window for this buffer and save some values */
+    // Find a window for this buffer and save some values.
     aucmd_prepbuf(&aco, buf);
+    set_bufref(&bufref, buf);
 
     bool did_aucmd;
     // execute the autocommands for this buffer
@@ -6317,9 +6331,10 @@ void ex_doautoall(exarg_T *eap)
     /* restore the current window */
     aucmd_restbuf(&aco);
 
-    /* stop if there is some error or buffer was deleted */
-    if (retval == FAIL || !buf_valid(buf))
+    // Stop if there is some error or buffer was deleted.
+    if (retval == FAIL || !bufref_valid(&bufref)) {
       break;
+    }
   }
 
   check_cursor();           /* just in case lines got deleted */
@@ -6426,7 +6441,7 @@ aucmd_prepbuf (
   }
   curbuf = buf;
   aco->new_curwin = curwin;
-  aco->new_curbuf = curbuf;
+  set_bufref(&aco->new_curbuf, curbuf);
 }
 
 /// Cleanup after executing autocommands for a (hidden) buffer.
@@ -6489,14 +6504,14 @@ win_found:
       // Restore the buffer which was previously edited by curwin, if it was
       // changed, we are still the same window and the buffer is valid.
       if (curwin == aco->new_curwin
-          && curbuf != aco->new_curbuf
-          && buf_valid(aco->new_curbuf)
-          && aco->new_curbuf->b_ml.ml_mfp != NULL) {
+          && curbuf != aco->new_curbuf.br_buf
+          && bufref_valid(&aco->new_curbuf)
+          && aco->new_curbuf.br_buf->b_ml.ml_mfp != NULL) {
         if (curwin->w_s == &curbuf->b_s) {
-          curwin->w_s = &aco->new_curbuf->b_s;
+          curwin->w_s = &aco->new_curbuf.br_buf->b_s;
         }
         curbuf->b_nwindows--;
-        curbuf = aco->new_curbuf;
+        curbuf = aco->new_curbuf.br_buf;
         curwin->w_buffer = curbuf;
         curbuf->b_nwindows++;
       }
diff --git a/src/nvim/fileio.h b/src/nvim/fileio.h
index ceb101167d..426dc0fcb3 100644
--- a/src/nvim/fileio.h
+++ b/src/nvim/fileio.h
@@ -19,12 +19,12 @@
  * not the current buffer.
  */
 typedef struct {
-  buf_T       *save_curbuf;     /* saved curbuf */
-  int use_aucmd_win;            /* using aucmd_win */
-  win_T       *save_curwin;     /* saved curwin */
-  win_T       *new_curwin;      /* new curwin */
-  buf_T       *new_curbuf;      /* new curbuf */
-  char_u      *globaldir;       /* saved value of globaldir */
+  buf_T       *save_curbuf;     ///< saved curbuf
+  int use_aucmd_win;            ///< using aucmd_win
+  win_T       *save_curwin;     ///< saved curwin
+  win_T       *new_curwin;      ///< new curwin
+  bufref_T     new_curbuf;      ///< new curbuf
+  char_u      *globaldir;       ///< saved value of globaldir
 } aco_save_T;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index baa85c01f8..9da6062ffb 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -512,9 +512,9 @@ EXTERN int keep_filetype INIT(= FALSE);         /* value for did_filetype when
                                                    starting to execute
                                                    autocommands */
 
-/* When deleting the current buffer, another one must be loaded.  If we know
- * which one is preferred, au_new_curbuf is set to it */
-EXTERN buf_T    *au_new_curbuf INIT(= NULL);
+// When deleting the current buffer, another one must be loaded.
+// If we know which one is preferred, au_new_curbuf is set to it.
+EXTERN bufref_T au_new_curbuf INIT(= { NULL, 0 });
 
 // When deleting a buffer/window and autocmd_busy is TRUE, do not free the
 // buffer/window. but link it in the list starting with
@@ -602,7 +602,10 @@ EXTERN buf_T    *lastbuf INIT(= NULL);   // last buffer
 EXTERN buf_T    *curbuf INIT(= NULL);    // currently active buffer
 
 // Iterates over all buffers in the buffer list.
-# define FOR_ALL_BUFFERS(buf) for (buf_T *buf = firstbuf; buf != NULL; buf = buf->b_next)
+#define FOR_ALL_BUFFERS(buf) \
+  for (buf_T *buf = firstbuf; buf != NULL; buf = buf->b_next)
+#define FOR_ALL_BUFFERS_BACKWARDS(buf) \
+  for (buf_T *buf = lastbuf; buf != NULL; buf = buf->b_prev)
 
 /* Flag that is set when switching off 'swapfile'.  It means that all blocks
  * are to be loaded into memory.  Shouldn't be global... */
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 6194e5f948..88c1990786 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -588,10 +588,13 @@ void getout(int exitval)
     /* Trigger BufUnload for buffers that are loaded */
     FOR_ALL_BUFFERS(buf) {
       if (buf->b_ml.ml_mfp != NULL) {
-        apply_autocmds(EVENT_BUFUNLOAD, buf->b_fname, buf->b_fname,
-            FALSE, buf);
-        if (!buf_valid(buf))            /* autocmd may delete the buffer */
+        bufref_T bufref;
+        set_bufref(&bufref, buf);
+        apply_autocmds(EVENT_BUFUNLOAD, buf->b_fname, buf->b_fname, false, buf);
+        if (!bufref_valid(&bufref)) {
+          // Autocmd deleted the buffer.
           break;
+        }
       }
     }
     apply_autocmds(EVENT_VIMLEAVEPRE, NULL, NULL, FALSE, curbuf);
diff --git a/src/nvim/memory.c b/src/nvim/memory.c
index 25fa2f150e..51e0dd926e 100644
--- a/src/nvim/memory.c
+++ b/src/nvim/memory.c
@@ -629,12 +629,12 @@ void free_all_mem(void)
    * were freed already. */
   p_acd = false;
   for (buf = firstbuf; buf != NULL; ) {
+    bufref_T bufref;
+    set_bufref(&bufref, buf);
     nextbuf = buf->b_next;
     close_buffer(NULL, buf, DOBUF_WIPE, false);
-    if (buf_valid(buf))
-      buf = nextbuf;            /* didn't work, try next one */
-    else
-      buf = firstbuf;
+    // Didn't work, try next one.
+    buf = bufref_valid(&bufref) ? nextbuf : firstbuf;
   }
 
   free_cmdline_buf();
diff --git a/src/nvim/option.c b/src/nvim/option.c
index a4e7da770e..a218323dac 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -5588,12 +5588,6 @@ void buf_copy_options(buf_T *buf, int flags)
   int did_isk = FALSE;
 
   /*
-   * Don't do anything if the buffer is invalid.
-   */
-  if (buf == NULL || !buf_valid(buf))
-    return;
-
-  /*
    * Skip this when the option defaults have not been set yet.  Happens when
    * main() allocates the first buffer.
    */
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index cebff5e8b7..c40403e3f6 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -1283,11 +1283,17 @@ void copy_loclist(win_T *from, win_T *to)
   to->w_llist->qf_curlist = qi->qf_curlist;     /* current list */
 }
 
+// Looking up a buffer can be slow if there are many. Remember the last one to
+// make this a lot faster if there are multiple matches in the same file.
+static char_u *qf_last_bufname = NULL;
+static bufref_T qf_last_bufref = { NULL, 0 };
+
 // Get buffer number for file "directory.fname".
 // Also sets the b_has_qf_entry flag.
 static int qf_get_fnum(qf_info_T *qi, char_u *directory, char_u *fname)
 {
-  char_u *ptr;
+  char_u *ptr = NULL;
+  char_u *bufname;
   buf_T *buf;
   if (fname == NULL || *fname == NUL) {         // no file name
     return 0;
@@ -1314,11 +1320,22 @@ static int qf_get_fnum(qf_info_T *qi, char_u *directory, char_u *fname)
         ptr = vim_strsave(fname);
       }
     }
-    // Use concatenated directory name and file name
-    buf = buflist_new(ptr, NULL, (linenr_T)0, 0);
+    // Use concatenated directory name and file name.
+    bufname = ptr;
+  } else {
+    bufname = fname;
+  }
+
+  if (qf_last_bufname != NULL
+      && STRCMP(bufname, qf_last_bufname) == 0
+      && bufref_valid(&qf_last_bufref)) {
+    buf = qf_last_bufref.br_buf;
     xfree(ptr);
   } else {
-    buf = buflist_new(fname, NULL, (linenr_T)0, 0);
+    xfree(qf_last_bufname);
+    buf = buflist_new(bufname, NULL, (linenr_T)0, BLN_NOOPT);
+    qf_last_bufname = (bufname == ptr) ? bufname : vim_strsave(bufname);
+    set_bufref(&qf_last_bufref, buf);
   }
   if (buf == NULL) {
     return 0;
@@ -3717,8 +3734,9 @@ load_dummy_buffer (
 )
 {
   buf_T       *newbuf;
-  buf_T       *newbuf_to_wipe = NULL;
-  int failed = TRUE;
+  bufref_T newbufref;
+  bufref_T newbuf_to_wipe;
+  int failed = true;
   aco_save_T aco;
 
   // Allocate a buffer without putting it in the buffer list.
@@ -3726,6 +3744,7 @@ load_dummy_buffer (
   if (newbuf == NULL) {
     return NULL;
   }
+  set_bufref(&newbufref, newbuf);
 
   /* Init the options. */
   buf_copy_options(newbuf, BCO_ENTER | BCO_NOHELP);
@@ -3745,6 +3764,7 @@ load_dummy_buffer (
      * work. */
     curbuf->b_flags &= ~BF_DUMMY;
 
+    newbuf_to_wipe.br_buf = NULL;
     if (readfile(fname, NULL,
             (linenr_T)0, (linenr_T)0, (linenr_T)MAXLNUM,
             NULL, READ_NEW | READ_DUMMY) == OK
@@ -3752,19 +3772,24 @@ load_dummy_buffer (
         && !(curbuf->b_flags & BF_NEW)) {
       failed = FALSE;
       if (curbuf != newbuf) {
-        /* Bloody autocommands changed the buffer!  Can happen when
-         * using netrw and editing a remote file.  Use the current
-         * buffer instead, delete the dummy one after restoring the
-         * window stuff. */
-        newbuf_to_wipe = newbuf;
+        // Bloody autocommands changed the buffer!  Can happen when
+        // using netrw and editing a remote file.  Use the current
+        // buffer instead, delete the dummy one after restoring the
+        // window stuff.
+        set_bufref(&newbuf_to_wipe, newbuf);
         newbuf = curbuf;
       }
     }
 
-    /* restore curwin/curbuf and a few other things */
+    // Restore curwin/curbuf and a few other things.
     aucmd_restbuf(&aco);
-    if (newbuf_to_wipe != NULL && buf_valid(newbuf_to_wipe))
-      wipe_buffer(newbuf_to_wipe, FALSE);
+    if (newbuf_to_wipe.br_buf != NULL && bufref_valid(&newbuf_to_wipe)) {
+      wipe_buffer(newbuf_to_wipe.br_buf, false);
+    }
+
+    // Add back the "dummy" flag, otherwise buflist_findname_file_id()
+    // won't skip it.
+    newbuf->b_flags |= BF_DUMMY;
   }
 
   /*
@@ -3775,8 +3800,9 @@ load_dummy_buffer (
   os_dirname(resulting_dir, MAXPATHL);
   restore_start_dir(dirname_start);
 
-  if (!buf_valid(newbuf))
+  if (!bufref_valid(&newbufref)) {
     return NULL;
+  }
   if (failed) {
     wipe_dummy_buffer(newbuf, dirname_start);
     return NULL;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 7e0bbd6ad1..1ace39344d 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -3746,6 +3746,9 @@ char_u *did_set_spelllang(win_T *wp)
   char_u      *ret_msg = NULL;
   char_u      *spl_copy;
 
+  bufref_T bufref;
+  set_bufref(&bufref, wp->w_buffer);
+
   // We don't want to do this recursively.  May happen when a language is
   // not available and the SpellFileMissing autocommand opens a new buffer
   // in which 'spell' is set.
@@ -3824,7 +3827,7 @@ char_u *did_set_spelllang(win_T *wp)
         spell_load_lang(lang);
         // SpellFileMissing autocommands may do anything, including
         // destroying the buffer we are using...
-        if (!buf_valid(wp->w_buffer)) {
+        if (!bufref_valid(&bufref)) {
           ret_msg =
             (char_u *)"E797: SpellFileMissing autocommand deleted buffer";
           goto theend;
@@ -13037,8 +13040,9 @@ void ex_spelldump(exarg_T *eap)
   set_option_value((char_u*)"spl",  dummy, spl, OPT_LOCAL);
   xfree(spl);
 
-  if (!bufempty() || !buf_valid(curbuf))
+  if (!bufempty()) {
     return;
+  }
 
   spell_dump_compl(NULL, 0, NULL, eap->forceit ? DUMPFLAG_COUNT : 0);
 
diff --git a/src/nvim/version.c b/src/nvim/version.c
index a12621d06f..e73b68b6e7 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -416,14 +416,14 @@ static int included_patches[] = {
   // 2027 NA
   // 2026 NA
   // 2025 NA
-  // 2024,
-  // 2023,
-  // 2022,
-  // 2021,
+  2024,
+  2023,
+  2022,
+  2021,
   // 2020 NA
   2019,
-  // 2018,
-  // 2017,
+  2018,
+  2017,
   // 2016 NA
   2015,
   2014,
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 801969a594..510f182353 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -1945,6 +1945,8 @@ int win_close(win_T *win, int free_buf)
    * Close the link to the buffer.
    */
   if (win->w_buffer != NULL) {
+    bufref_T bufref;
+    set_bufref(&bufref, curbuf);
     win->w_closing = true;
     close_buffer(win, win->w_buffer, free_buf ? DOBUF_UNLOAD : 0, true);
     if (win_valid_any_tab(win)) {
@@ -1953,7 +1955,7 @@ int win_close(win_T *win, int free_buf)
 
     // Make sure curbuf is valid. It can become invalid if 'bufhidden' is
     // "wipe".
-    if (!buf_valid(curbuf)) {
+    if (!bufref_valid(&bufref)) {
       curbuf = firstbuf;
     }
   }
@@ -5401,32 +5403,30 @@ void restore_win(win_T *save_curwin, tabpage_T *save_curtab, int no_display)
   unblock_autocmds();
 }
 
-/*
- * Make "buf" the current buffer.  restore_buffer() MUST be called to undo.
- * No autocommands will be executed.  Use aucmd_prepbuf() if there are any.
- */
-void switch_buffer(buf_T **save_curbuf, buf_T *buf)
+/// Make "buf" the current buffer.
+///
+/// restore_buffer() MUST be called to undo.
+/// No autocommands will be executed. Use aucmd_prepbuf() if there are any.
+void switch_buffer(bufref_T *save_curbuf, buf_T *buf)
 {
   block_autocmds();
-  *save_curbuf = curbuf;
-  --curbuf->b_nwindows;
+  set_bufref(save_curbuf, curbuf);
+  curbuf->b_nwindows--;
   curbuf = buf;
   curwin->w_buffer = buf;
-  ++curbuf->b_nwindows;
+  curbuf->b_nwindows++;
 }
 
-/*
- * Restore the current buffer after using switch_buffer().
- */
-void restore_buffer(buf_T *save_curbuf)
+/// Restore the current buffer after using switch_buffer().
+void restore_buffer(bufref_T *save_curbuf)
 {
   unblock_autocmds();
-  /* Check for valid buffer, just in case. */
-  if (buf_valid(save_curbuf)) {
-    --curbuf->b_nwindows;
-    curwin->w_buffer = save_curbuf;
-    curbuf = save_curbuf;
-    ++curbuf->b_nwindows;
+  // Check for valid buffer, just in case.
+  if (bufref_valid(save_curbuf)) {
+    curbuf->b_nwindows--;
+    curwin->w_buffer = save_curbuf->br_buf;
+    curbuf = save_curbuf->br_buf;
+    curbuf->b_nwindows++;
   }
 }