bug#23223: 25.0.92; Can xref-find-references be sped up?

[Dmitry Gutov <dgutov@yandex.ru>]

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On 04/11/2016 06:56 PM, Eli Zaretskii wrote:

> Unfortunately, it seems to miss matches: out of 1127 matches of
> current_buffer with the original version, the new one only shows 963.
> It sounds like some conditions on what exactly is a symbol need
> adjustment,

Ooh, that's a great catch, thanks! Turns out, auto-mode-alist wasn't 
getting applied because buffer-file-name wasn't set. Fixing that added 
~25% performance hit, so I also added xref--find-buffer-visiting to 
cache the expensive lookup mentioned previously. See the new patch attached.

That seems to about exhaust the optimization opportunity here.

> As an aside, if I invoke xref-find-references without an ID file,
> which AFAIU means Emacs will invoke find+grep, I get this error:
>
>   semantic-symref-derive-find-filepatterns: Customize ‘semantic-symref-filepattern-alist’ for lisp-interaction-mode
>
> unless I invoke xref-find-references from a buffer in C mode.

...or the current major mode is one of the currently supported ones, via 
the above variable.

> Curiously, this doesn't happen when there's an ID file and IDutils is
> invoked.  Is this expected?

Yes. semantic-symref-filepattern-alist is defined in and used by 
semantic/symref/grep.el. We can add (lisp-interaction-mode "*.el") to it.

> "gid" is just a short for "lid -R grep", so the
> contents I get is the same as xref-find-references does, it's just
> formatted differently.

Not exactly: you get more false positives because it doesn't apply the 
language-aware filtering.

>> What's the new time you get from the former?
>
> 3 sec (in an unoptimized build, I'd expect this to become 1 sec in an
> optimized build).  So we are OK speed-wise, we just need to fix the
> misses mentioned above.

Cool.

>> By the way, the "insert-file-contents + set-auto-mode" dance comes with
>> a new minor downside: extra chatter from the major modes. E.g. try
>> project-file-regexp with "should have received a copy".
>
> I don't see this in xref-find-references.  Should I?

Not at all. xref-find-references only searches in the files related to 
the current one by type (or in a predefined database like id-utils's one).

The chatter I got was from e.g. sh-mode (about the indentation variable 
being guessed), nxml-mode, and so on, with matches in ~4000 files.

>> We can avoid saving it to the message log, but it appears in the
>> echo area either way.
>
> Can't you bind inhibit-message to a non-nil value?

That works!

> Thanks again for working on this.

Thanks for the thoughtful bug report.

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diff --git a/lisp/cedet/semantic/symref/cscope.el b/lisp/cedet/semantic/symref/cscope.el
index 4890b5b..3abd8b3 100644
--- a/lisp/cedet/semantic/symref/cscope.el
+++ b/lisp/cedet/semantic/symref/cscope.el
@@ -60,6 +60,9 @@ semantic-symref-tool-cscope
     (semantic-symref-parse-tool-output tool b)
     ))
 
+(defconst semantic-symref-cscope--line-re
+  "^\\([^ ]+\\) [^ ]+ \\([0-9]+\\) ")
+
 (cl-defmethod semantic-symref-parse-tool-output-one-line ((tool semantic-symref-tool-cscope))
   "Parse one line of grep output, and return it as a match list.
 Moves cursor to end of the match."
@@ -78,8 +81,13 @@ semantic-symref-tool-cscope
 	       ;; We have to return something at this point.
 	       subtxt)))
 	 )
-	(t
-	 (when (re-search-forward "^\\([^ ]+\\) [^ ]+ \\([0-9]+\\) " nil t)
+        ((eq (oref tool :resulttype) 'line-and-text)
+         (when (re-search-forward semantic-symref-cscope--line-re nil t)
+           (list (string-to-number (match-string 2))
+                 (expand-file-name (match-string 1))
+                 (buffer-substring-no-properties (point) (line-end-position)))))
+	(t ; :resulttype is 'line
+	 (when (re-search-forward semantic-symref-cscope--line-re nil t)
 	   (cons (string-to-number (match-string 2))
 		 (expand-file-name (match-string 1)))
 	   ))))
diff --git a/lisp/cedet/semantic/symref/global.el b/lisp/cedet/semantic/symref/global.el
index e4c114e..a33427e 100644
--- a/lisp/cedet/semantic/symref/global.el
+++ b/lisp/cedet/semantic/symref/global.el
@@ -49,6 +49,9 @@ semantic-symref-tool-global
     (semantic-symref-parse-tool-output tool b)
     ))
 
+(defconst semantic-symref-global--line-re
+  "^\\([^ ]+\\) +\\([0-9]+\\) \\([^ ]+\\) ")
+
 (cl-defmethod semantic-symref-parse-tool-output-one-line ((tool semantic-symref-tool-global))
   "Parse one line of grep output, and return it as a match list.
 Moves cursor to end of the match."
@@ -57,8 +60,13 @@ semantic-symref-tool-global
 	 ;; Search for files
 	 (when (re-search-forward "^\\([^\n]+\\)$" nil t)
 	   (match-string 1)))
+        ((eq (oref tool :resulttype) 'line-and-text)
+         (when (re-search-forward semantic-symref-global--line-re nil t)
+           (list (string-to-number (match-string 2))
+                 (match-string 3)
+                 (buffer-substring-no-properties (point) (line-end-position)))))
 	(t
-	 (when (re-search-forward "^\\([^ ]+\\) +\\([0-9]+\\) \\([^ ]+\\) " nil t)
+	 (when (re-search-forward semantic-symref-global--line-re nil t)
 	   (cons (string-to-number (match-string 2))
 		 (match-string 3))
 	   ))))
diff --git a/lisp/cedet/semantic/symref/grep.el b/lisp/cedet/semantic/symref/grep.el
index 5d1fea8..868e6c3 100644
--- a/lisp/cedet/semantic/symref/grep.el
+++ b/lisp/cedet/semantic/symref/grep.el
@@ -188,6 +188,9 @@ semantic-symref-grep-shell
     ;; Return the answer
     ans))
 
+(defconst semantic-symref-grep--line-re
+  "^\\(\\(?:[a-zA-Z]:\\)?[^:\n]+\\):\\([0-9]+\\):")
+
 (cl-defmethod semantic-symref-parse-tool-output-one-line ((tool semantic-symref-tool-grep))
   "Parse one line of grep output, and return it as a match list.
 Moves cursor to end of the match."
@@ -195,8 +198,13 @@ semantic-symref-grep-shell
 	 ;; Search for files
 	 (when (re-search-forward "^\\([^\n]+\\)$" nil t)
 	   (match-string 1)))
+        ((eq (oref tool :resulttype) 'line-and-text)
+         (when (re-search-forward semantic-symref-grep--line-re nil t)
+           (list (string-to-number (match-string 2))
+                 (match-string 1)
+                 (buffer-substring-no-properties (point) (line-end-position)))))
 	(t
-	 (when (re-search-forward  "^\\(\\(?:[a-zA-Z]:\\)?[^:\n]+\\):\\([0-9]+\\):" nil t)
+	 (when (re-search-forward semantic-symref-grep--line-re nil t)
 	   (cons (string-to-number (match-string 2))
 		 (match-string 1))
 	   ))))
diff --git a/lisp/cedet/semantic/symref/idutils.el b/lisp/cedet/semantic/symref/idutils.el
index 4127d7a..db3e9a0 100644
--- a/lisp/cedet/semantic/symref/idutils.el
+++ b/lisp/cedet/semantic/symref/idutils.el
@@ -49,6 +49,9 @@ semantic-symref-tool-idutils
     (semantic-symref-parse-tool-output tool b)
     ))
 
+(defconst semantic-symref-idutils--line-re
+  "^\\(\\(?:[a-zA-Z]:\\)?[^:\n]+\\):\\([0-9]+\\):")
+
 (cl-defmethod semantic-symref-parse-tool-output-one-line ((tool semantic-symref-tool-idutils))
   "Parse one line of grep output, and return it as a match list.
 Moves cursor to end of the match."
@@ -59,8 +62,13 @@ semantic-symref-tool-idutils
 	((eq (oref tool :searchtype) 'tagcompletions)
 	 (when (re-search-forward "^\\([^ ]+\\) " nil t)
 	   (match-string 1)))
-	(t
-	 (when (re-search-forward "^\\(\\(?:[a-zA-Z]:\\)?[^:\n]+\\):\\([0-9]+\\):" nil t)
+        ((eq (oref tool :resulttype) 'line-and-text)
+         (when (re-search-forward semantic-symref-idutils--line-re nil t)
+	   (list (string-to-number (match-string 2))
+                 (expand-file-name (match-string 1) default-directory)
+                 (buffer-substring-no-properties (point) (line-end-position)))))
+	(t ; resulttype is line
+	 (when (re-search-forward semantic-symref-idutils--line-re nil t)
 	   (cons (string-to-number (match-string 2))
 		 (expand-file-name (match-string 1) default-directory))
 	   ))))
diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index feed0fb..68021c5 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -839,16 +839,18 @@ xref-etags-mode
         (kill-local-variable 'xref-backend-functions))
     (setq-local xref-backend-functions xref-etags-mode--saved)))
 
-(declare-function semantic-symref-find-references-by-name "semantic/symref")
-(declare-function semantic-find-file-noselect "semantic/fw")
+(declare-function semantic-symref-instantiate "semantic/symref")
+(declare-function semantic-symref-perform-search "semantic/symref")
 (declare-function grep-expand-template "grep")
 (defvar ede-minor-mode) ;; ede.el
 
+(defvar xref--last-visiting-buffer nil)
+
 (defun xref-collect-references (symbol dir)
   "Collect references to SYMBOL inside DIR.
 This function uses the Semantic Symbol Reference API, see
-`semantic-symref-find-references-by-name' for details on which
-tools are used, and when."
+`semantic-symref-tool-alist' for details on which tools are used,
+and when."
   (cl-assert (directory-name-p dir))
   (require 'semantic/symref)
   (defvar semantic-symref-tool)
@@ -859,19 +861,26 @@ xref-collect-references
   ;; to force the backend to use `default-directory'.
   (let* ((ede-minor-mode nil)
          (default-directory dir)
+         ;; FIXME: Remove CScope and Global from the recognized tools?
+         ;; The current implementations interpret the symbol search as
+         ;; "find all calls to the given function", but not function
+         ;; definition. And they return nothing when passed a variable
+         ;; name, even a global one.
          (semantic-symref-tool 'detect)
          (case-fold-search nil)
-         (res (semantic-symref-find-references-by-name symbol 'subdirs))
-         (hits (and res (oref res hit-lines)))
-         (orig-buffers (buffer-list)))
+         (inst (semantic-symref-instantiate :searchfor symbol
+                                            :searchtype 'symbol
+                                            :searchscope 'subdirs
+                                            :resulttype 'line-and-text))
+         (hits (semantic-symref-perform-search inst))
+         xref--last-visiting-buffer
+         (tmp-buffer (generate-new-buffer " *xref-temp*")))
     (unwind-protect
         (cl-mapcan (lambda (hit) (xref--collect-matches
-                             hit (format "\\_<%s\\_>" (regexp-quote symbol))))
+                             hit (format "\\_<%s\\_>" (regexp-quote symbol))
+                             tmp-buffer))
                    hits)
-      ;; TODO: Implement "lightweight" buffer visiting, so that we
-      ;; don't have to kill them.
-      (mapc #'kill-buffer
-            (cl-set-difference (buffer-list) orig-buffers)))))
+      (kill-buffer tmp-buffer))))
 
 ;;;###autoload
 (defun xref-collect-matches (regexp files dir ignores)
@@ -890,34 +899,25 @@ xref-collect-matches
                                        files
                                        (expand-file-name dir)
                                        ignores))
-         (orig-buffers (buffer-list))
          (buf (get-buffer-create " *xref-grep*"))
          (grep-re (caar grep-regexp-alist))
-         (counter 0)
-         reporter
-         hits)
+         hits
+         xref--last-visiting-buffer
+         (tmp-buffer (generate-new-buffer " *xref-temp*")))
     (with-current-buffer buf
       (erase-buffer)
       (call-process-shell-command command nil t)
       (goto-char (point-min))
       (while (re-search-forward grep-re nil t)
-        (push (cons (string-to-number (match-string 2))
-                    (match-string 1))
+        (push (list (string-to-number (match-string 2))
+                    (match-string 1)
+                    (buffer-substring-no-properties (point) (line-end-position)))
               hits)))
-    (setq reporter (make-progress-reporter
-                    (format "Collecting search results...")
-                    0 (length hits)))
     (unwind-protect
         (cl-mapcan (lambda (hit)
-                     (prog1
-                         (progress-reporter-update reporter counter)
-                       (cl-incf counter))
-                     (xref--collect-matches hit regexp))
+                     (xref--collect-matches hit regexp tmp-buffer))
                    (nreverse hits))
-      (progress-reporter-done reporter)
-      ;; TODO: Same as above.
-      (mapc #'kill-buffer
-            (cl-set-difference (buffer-list) orig-buffers)))))
+      (kill-buffer tmp-buffer))))
 
 (defun xref--rgrep-command (regexp files dir ignores)
   (require 'find-dired)      ; for `find-name-arg'
@@ -980,30 +980,60 @@ xref--regexp-to-extended
                (match-string 1 str)))))
    str t t))
 
-(defun xref--collect-matches (hit regexp)
-  (pcase-let* ((`(,line . ,file) hit)
-               (buf (or (find-buffer-visiting file)
-                        (semantic-find-file-noselect file))))
-    (with-current-buffer buf
-      (save-excursion
+(defvar xref--temp-buffer-file-name nil)
+
+(defun xref--collect-matches (hit regexp tmp-buffer)
+  (pcase-let* ((`(,line ,file ,text) hit)
+               (buf (xref--find-buffer-visiting file)))
+    (if buf
+        (with-current-buffer buf
+          (save-excursion
+            (goto-char (point-min))
+            (forward-line (1- line))
+            (xref--collect-matches-1 regexp file line
+                                     (line-beginning-position)
+                                     (line-end-position))))
+      (with-current-buffer tmp-buffer
+        (erase-buffer)
+        (unless (equal file xref--temp-buffer-file-name)
+          (insert-file-contents file nil 0 200)
+          ;; Can't (setq-local delay-mode-hooks t) because of
+          ;; bug#23272, but the performance penalty seems minimal.
+          (let ((buffer-file-name file)
+                (inhibit-message t)
+                message-log-max)
+            (ignore-errors
+              (set-auto-mode t)))
+          (setq-local xref--temp-buffer-file-name file)
+          (setq-local inhibit-read-only t)
+          (erase-buffer))
+        (insert text)
         (goto-char (point-min))
-        (forward-line (1- line))
-        (let ((line-end (line-end-position))
-              (line-beg (line-beginning-position))
-              matches)
-          (syntax-propertize line-end)
-          ;; FIXME: This results in several lines with the same
-          ;; summary. Solve with composite pattern?
-          (while (re-search-forward regexp line-end t)
-            (let* ((beg-column (- (match-beginning 0) line-beg))
-                   (end-column (- (match-end 0) line-beg))
-                   (loc (xref-make-file-location file line beg-column))
-                   (summary (buffer-substring line-beg line-end)))
-              (add-face-text-property beg-column end-column 'highlight
-                                      t summary)
-              (push (xref-make-match summary loc (- end-column beg-column))
-                    matches)))
-          (nreverse matches))))))
+        (xref--collect-matches-1 regexp file line
+                                 (point)
+                                 (point-max))))))
+
+(defun xref--collect-matches-1 (regexp file line line-beg line-end)
+  (let (matches)
+    (syntax-propertize line-end)
+    ;; FIXME: This results in several lines with the same
+    ;; summary. Solve with composite pattern?
+    (while (re-search-forward regexp line-end t)
+      (let* ((beg-column (- (match-beginning 0) line-beg))
+             (end-column (- (match-end 0) line-beg))
+             (loc (xref-make-file-location file line beg-column))
+             (summary (buffer-substring line-beg line-end)))
+        (add-face-text-property beg-column end-column 'highlight
+                                t summary)
+        (push (xref-make-match summary loc (- end-column beg-column))
+              matches)))
+    (nreverse matches)))
+
+(defun xref--find-buffer-visiting (file)
+  (unless (equal (car xref--last-visiting-buffer) file)
+    (setq xref--last-visiting-buffer
+          (cons file (find-buffer-visiting file))))
+  (cdr xref--last-visiting-buffer))
 
 (provide 'xref)