From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Dmitry Gutov <dgutov@yandex.ru>
Cc: 15294@debbugs.gnu.org
Subject: bug#15294: 24.3.50; js2-mode parser is several times slower in lexical-binding mode
Date: Sun, 15 Sep 2013 01:04:22 -0400 [thread overview]
Message-ID: <jwvtxhmk7ty.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <5234FB3D.40209@yandex.ru> (Dmitry Gutov's message of "Sun, 15 Sep 2013 03:11:41 +0300")
> Can the fact that `dotimes', `dolist' and `loop' are advised with
> cl--wrap-in-nil-block', which expands into `catch' form, make much
> of a difference?
No, these only expand to `catch' if there's a `return' inside.
> `js2-get-token' has 13 local variables (*). Which is, while not a little,
> far from 100. Most of the other functions have fewer than that.
I don't know how many it takes to be significantly slower than `symbol-value'.
> Are you counting the global variables, too?
No. But arguments, yes, and every (defvar <var>) between point and BOB
as well.
> The dynamic-binding interpreter has to work with them, too. How is it
> that much faster?
Dynamic binding lookup is done by `symbol-value' which is just a field
access (plus checking that the var is not special (e.g. buffer-local or
a predefined C variable).
>>> But 2.6 vs 2.1, it still a noticeable regression. Do you suppose the usage
>>> of `setq' is the main contributor?
>> The problem goes as follows: ...
> Thank you for the detailed explanation.
> There are a few `catch' forms left there, for tags `continue' and `break',
> used for control flow. So, most of the 0.5s difference left is likely due to
> them, right?
The problem is not just the use of catch, but the combination of "catch"
with all those vars let-bound outside of catch, used inside, and mutated:
- make a variable immutable (i.e. remove the setqs on it) and that
variable becomes more efficient again.
- move the let binding inside the catch, and the var becomes efficient again.
- don't use the variable inside the catch, and it becomes efficient again.
Stefan
next prev parent reply other threads:[~2013-09-15 5:04 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-06 20:59 bug#15294: 24.3.50; js2-mode parser is several times slower in lexical-binding mode Dmitry Gutov
2013-09-06 23:44 ` Xue Fuqiao
2013-09-07 3:15 ` Stefan Monnier
2013-09-08 22:32 ` Stefan Monnier
2013-09-10 2:04 ` Stefan Monnier
2013-09-13 3:40 ` Stefan Monnier
2013-09-13 3:59 ` Drew Adams
2013-09-13 4:37 ` Stefan Monnier
2013-09-13 5:45 ` Drew Adams
2013-09-13 13:01 ` Stefan Monnier
2013-09-14 0:09 ` Lexical let and setq Michael Welsh Duggan
2013-09-14 3:46 ` Stefan Monnier
2013-09-14 11:13 ` Lars Magne Ingebrigtsen
2013-09-14 14:04 ` Pascal J. Bourguignon
2013-09-15 5:11 ` Stefan Monnier
2013-09-14 21:47 ` Richard Stallman
2013-09-15 5:09 ` Stefan Monnier
2013-09-15 16:54 ` Richard Stallman
2013-09-15 17:06 ` Stefan Monnier
2013-09-16 10:47 ` Richard Stallman
2013-09-14 4:20 ` bug#15294: 24.3.50; js2-mode parser is several times slower in lexical-binding mode Dmitry Gutov
2013-09-14 14:27 ` Stefan Monnier
2013-09-15 0:11 ` Dmitry Gutov
2013-09-15 5:04 ` Stefan Monnier [this message]
2013-09-15 16:54 ` Richard Stallman
2013-09-15 0:24 ` Dmitry Gutov
2013-09-15 5:06 ` Stefan Monnier
2013-09-18 23:48 ` Stefan Monnier
2013-09-22 4:56 ` Dmitry Gutov
2013-10-03 5:00 ` Stefan Monnier
2013-10-04 2:38 ` Dmitry Gutov
2013-10-04 13:52 ` Stefan Monnier
2013-10-05 3:27 ` Dmitry Gutov
2014-12-14 12:31 ` Dmitry Gutov
2014-12-14 14:08 ` Stefan Monnier
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