Re: master 289000e: Merge branch 'feature/native-comp' into trunk

[Alan Mackenzie]

Hello, Eli.

On Mon, Apr 26, 2021 at 20:25:17 +0300, Eli Zaretskii wrote:
> > Date: Mon, 26 Apr 2021 17:02:44 +0000
> > Cc: akrl@sdf.org, emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > Put point at the start of xdisp.c (or any other large file), optionally
> > type and delete a space (to clear font-lock text properties), and do M-:
> > (time-scroll).  This scrolls through the buffer one screenful at a time,
> > displaying each screenful, then reports the total time.


> > I've come to the conclusion in the last hour or so that CC Mode just
> > isn't sped up much at all by native compilation.  Using Andrea's tip of
> > C-h f c-mode + look for "natively compiled", it is clear that the
> > natively compiled files _are_ being used.

> Yes, for this benchmark, I find the natively-compiled code somewhat
> (by about 5%) _slower_ than the byte-compiled code.  But this
> benchmark only shows off the fontifications, so maybe it isn't
> surprising.  CC Mode is much more than that.

I wrote another benchmark which removes all indentation, then reindents
every line:

(defmacro time-it (&rest forms)
  "Time the running of a sequence of forms using `float-time'.
Call like this: \"M-: (time-it (foo ...) (bar ...) ...)\"."
  `(let ((start (float-time)))
    ,@forms
    (- (float-time) start)))

(defun time-indent ()
  (interactive)
  (save-excursion
    (goto-char (point-min))
    (while (not (eobp))
      (delete-horizontal-space)
      (beginning-of-line 2))
    (goto-char (point-min))
    (message "%s"
             (time-it
              (while (not (eobp))
                (c-indent-line)
                (beginning-of-line 2))))))

Run with M-: (time-indent).

The timings on src/minibuf.c were:
(i) .elc files: 6.31s.
(ii) .eln files: 5.44s.

, which is around a 13% speed up.

-- 
Alan Mackenzie (Nuremberg, Germany).