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From: Alan Mackenzie <acm@muc.de>
To: Gemini Lasswell <gazally@runbox.com>
Cc: "Clément Pit-Claudel" <cpitclaudel@gmail.com>,
	"Paul Eggert" <eggert@cs.ucla.edu>,
	michael_heerdegen@web.de, emacs-devel@gnu.org,
	monnier@IRO.UMontreal.CA, "Eli Zaretskii" <eliz@gnu.org>
Subject: Re: scratch/accurate-warning-pos: Solid progress: the branch now bootstraps.
Date: Tue, 27 Nov 2018 01:45:02 +0000	[thread overview]
Message-ID: <20181127014502.GA4732@ACM> (raw)
In-Reply-To: <8736rnib0k.fsf@runbox.com>

Hello, Gemini.

On Mon, Nov 26, 2018 at 17:07:07 -0800, Gemini Lasswell wrote:
> Alan Mackenzie <acm@muc.de> writes:

> Hi Alan,

> > Mainly because of EQ, the C macro corresponding to `eq'.  In master, EQ
> > just does a binary comparison between two Lisp_Objects, and that's it.
> > In scratch/accurate-warning-pos, should that binary comparison fail, EQ
> > additionally has to check the flag variable `symbols-with-pos-enabled'
> > to see whether it needs to do any additional comparisons.  Except while
> > byte compiling, it won't, but the check of that variable is what is
> > causing the slowdown.

> I'm having trouble accepting that this is the problem.

> When I hear a story about a C program, where adding an always failing
> check of a boolean variable to it causes it to run slower by 15% or 20%,
> then when I read the code I expect to find that variable check inside a
> really tight loop with only a few other instructions besides the
> variable check.

> But Fforward_word is significantly slower in your branch and I can't
> find any tight loops with an EQ in it.  exec_byte_code might fit that
> description, if you gave it a Lisp function with a loop that hammered on
> 'eq', but that doesn't describe fill-region-as-paragraph, which is 15%
> slower.  Could there be anything else causing a slowdown besides EQ?

In ..../src/lisp.h, we have:

    INLINE bool
    (NILP) (Lisp_Object x)
    {
      return lisp_h_NILP (x);
    }

, and earlier on in the file, we have

    #define lisp_h_NILP(x) EQ (x, Qnil).

So every NILP is substituted by EQ (x, Qnil).  There are a fair number
of NILPs in loops in Fforward_char and its subroutines.

> >> Another related question: this work is for warnings, but will it
> >> extend to having positions in backtraces?
> >
> > I hadn't actually got to thinking about that, but the answer is
> > proabably not, at least for now.  The .elc format for compiled functions
> > has a single entry for "each" symbol in its constant vector, and it
> > would be quite an exercise to augment that with symbols-with-position.
> >
> > Maybe for the future.

> Positions in error messages would be a major improvement as well.

Yes.  I wonder why this wasn't done long ago.

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2018-11-27  1:45 UTC|newest]

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-17 12:45 scratch/accurate-warning-pos: First tentative successes Alan Mackenzie
2018-11-17 13:13 ` Eli Zaretskii
2018-11-23 13:09   ` scratch/accurate-warning-pos: Solid progress: the branch now bootstraps Alan Mackenzie
2018-11-25 11:26     ` Charles A. Roelli
2018-11-25 14:31       ` Alan Mackenzie
2018-11-25 15:12         ` Andreas Schwab
2018-11-25 15:42           ` Alan Mackenzie
2018-11-25 16:40             ` Eli Zaretskii
2018-11-25 17:59               ` Alan Mackenzie
2018-11-25 18:15                 ` Eli Zaretskii
2018-11-25 18:23                   ` Alan Mackenzie
2018-11-25 19:36                     ` Alan Mackenzie
2018-11-25 16:22         ` Stefan Monnier
2018-11-25 17:35           ` Alan Mackenzie
2018-11-25 18:22             ` Stefan Monnier
2018-11-25 19:54               ` Alan Mackenzie
2018-11-25 20:08                 ` Stefan Monnier
2018-11-26  9:52                   ` Alan Mackenzie
2018-11-26 10:16                     ` Alan Mackenzie
2018-11-25 16:38         ` Eli Zaretskii
2018-11-25 17:27           ` Andreas Schwab
2018-11-25 17:31           ` Alan Mackenzie
2018-11-25 17:39             ` Eli Zaretskii
2018-11-25 18:08               ` Alan Mackenzie
2018-11-25 18:45       ` Paul Eggert
2018-11-25 19:30         ` Alan Mackenzie
2018-11-25 20:12           ` Paul Eggert
2018-11-25 21:29             ` Alan Mackenzie
2018-11-26  1:41               ` Paul Eggert
2018-11-26  3:41                 ` Eli Zaretskii
2018-11-26 17:43                   ` Paul Eggert
2018-11-26 18:43                     ` Alan Mackenzie
2018-11-26 19:18                       ` Clément Pit-Claudel
2018-11-26 19:42                         ` Alan Mackenzie
2018-11-27  1:07                           ` Gemini Lasswell
2018-11-27  1:45                             ` Alan Mackenzie [this message]
2018-11-27  6:06                             ` Eli Zaretskii
2018-11-27  2:48                       ` Paul Eggert
2018-11-27  7:43                         ` Alan Mackenzie
2018-11-27 20:27                           ` Paul Eggert
2018-11-27 21:15                             ` Alan Mackenzie
2018-11-27 21:37                               ` Paul Eggert
2018-11-27 21:53                                 ` Alan Mackenzie
2018-11-28  1:11                                   ` Paul Eggert
2018-11-28 12:04                                     ` Alan Mackenzie
2018-11-29 21:28                                       ` Paul Eggert
2018-11-29 22:05                                         ` Alan Mackenzie
2018-11-30 17:50                                           ` Paul Eggert
2018-11-30 18:55                                             ` Alan Mackenzie
2018-11-30 20:14                                               ` Paul Eggert
2018-11-30 22:02                                                 ` Alan Mackenzie
2018-11-30 23:46                                                   ` Paul Eggert
2018-12-01  7:35                                                     ` martin rudalics
2018-12-01  8:25                                                       ` Eli Zaretskii
2018-12-01 11:08                                                         ` Alan Mackenzie
2018-12-01 11:36                                                           ` Eli Zaretskii
2018-12-01 12:47                                                       ` Alan Mackenzie
2018-12-01 14:09                                                         ` martin rudalics
2018-12-01 14:30                                                           ` Stefan Monnier
2018-12-01 16:30                                                             ` martin rudalics
2018-12-01 19:56                                                               ` Stefan Monnier
2018-12-01 14:59                                                           ` Eli Zaretskii
2018-12-01 16:31                                                             ` martin rudalics
2018-12-01 16:53                                                               ` Eli Zaretskii
2018-12-01 19:04                                                                 ` martin rudalics
2018-12-01 19:22                                                                   ` Eli Zaretskii
2018-12-01 17:21                                                           ` Alan Mackenzie
2018-12-01 17:44                                                             ` Michael Heerdegen
2018-12-01 18:58                                                               ` Alan Mackenzie
2018-12-01 20:26                                                                 ` Alan Mackenzie
2018-12-01 17:48                                                             ` Eli Zaretskii
2018-12-01 21:00                                                               ` Paul Eggert
2018-12-01 17:50                                                             ` Clément Pit-Claudel
2018-12-01 18:26                                                               ` Yuri Khan
2018-12-01 19:15                                                                 ` Clément Pit-Claudel
2018-12-01 21:26                                                                 ` Paul Eggert
2018-12-02  6:48                                                                   ` Yuri Khan
2018-12-02 18:39                                                                   ` Gemini Lasswell
2018-12-03  2:28                                                                     ` Stefan Monnier
2018-12-01 19:04                                                             ` martin rudalics
2018-12-02 22:53                                                             ` Dmitry Gutov
2018-12-01  0:26                                               ` Gemini Lasswell
2018-12-01 11:48                                                 ` Alan Mackenzie
2018-11-27 22:09                                 ` Stefan Monnier
2018-11-28  2:18                                   ` Paul Eggert
2018-11-28  2:43                                     ` Stefan Monnier
2018-11-28  5:13                                       ` Paul Eggert
2018-11-28  6:03                                       ` Gemini Lasswell
2018-11-28  5:39                                   ` Gemini Lasswell
2018-11-28 13:06                                     ` Stefan Monnier
2018-11-28  6:28                                 ` Eli Zaretskii
2018-11-28 22:50                                   ` Paul Eggert
2018-11-29  7:19                                     ` Eli Zaretskii
2018-11-29 10:54                                     ` Alan Mackenzie
2018-11-29 11:13                                       ` Eli Zaretskii
2018-11-29 11:37                                         ` Alan Mackenzie
2018-11-29 21:12                                           ` Paul Eggert
2018-11-29 21:28                                             ` Alan Mackenzie
2018-11-28  0:53                               ` Gemini Lasswell
2018-11-26 20:04                     ` Stefan Monnier
2018-11-27  2:51                       ` Paul Eggert
2018-11-26  9:48                 ` Alan Mackenzie
2018-11-26 18:27                   ` Paul Eggert
2018-11-25 18:48     ` Gemini Lasswell
2018-11-25 20:02       ` Stefan Monnier
2018-11-26 12:39       ` Alan Mackenzie
2018-11-26 16:14         ` Gemini Lasswell
2018-11-26 17:06           ` Alan Mackenzie
2018-11-26 17:24             ` Alan Mackenzie
2018-11-29 12:26     ` scratch/accurate-warning-pos: Some real world timings Alan Mackenzie

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