From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Zach Shaftel <zshaftel@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Update 1 on Bytecode Offset tracking
Date: Fri, 17 Jul 2020 12:20:06 -0400 [thread overview]
Message-ID: <jwvtuy6kts0.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <87blkfoz9v.fsf@gmail.com> (Zach Shaftel's message of "Thu, 16 Jul 2020 18:45:00 -0400")
> Great! I just followed up on my copyright assignment as I still haven't
> finished that process. I don't know whether this could be exempt or if
> Rocky's assignment is sufficient, but hopefully I will hear back from
> copyright-clerk soon.
While waiting for the paperwork to go through, you can prepare the patch
and we can start discussing it.
> That seems to be the case. I'll keep looking to see if there's any low
> hanging fruit in terms of splitting up the funcall logic without slowing
> things down. More testing is necessary, but if a moderate chunk of
> duplicated code is acceptable then there may not be as much work needed
> on that branch as I had thought.
It's a tradeoff, so it's hard to say what is acceptable without seeing
the actual path along with the corresponding measurements of the
performance impact.
> Rough tests indicate it's about three times slower.
Wow! That's a lot less than I expected. That makes it quite usable.
This said, we'll probably still want to merge the feature into the
C code simply to avoid the duplication (I expect that the Edebug reader
has never been 100% faithful and that it has probably diverged over
time).
> Removing the string did improve performance, but not by as much as I
> expected. The function that constructs the tree of "children" may be
> slower than it needs to be, so I'll look into improving that. It may not
> be necessary to create the children for vectors since they're constants
> (outside of backquote, at least).
I think vectors are rare enough that the performance benefit of special
casing them is not worth the downside of losing source-location info
when it'd be beneficial.
> Yes, and it won't be easy to maintain the read locations across
> macroexpansion, byte-opt and cconv.
For byte-opt and cconv it's mostly a question of labour.
For macros, OTOH, it's really fundamentally hard (or impossible, in
general). We could/should introduce some new way to define macros which
knows about "source code annotated with locations".
There's a lot of work on Scheme macros we could leverage for that.
Stefan
next prev parent reply other threads:[~2020-07-17 16:20 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-15 23:10 Update 1 on Bytecode Offset tracking Zach Shaftel
2020-07-16 3:55 ` Stefan Monnier
2020-07-16 22:45 ` Zach Shaftel
2020-07-17 3:44 ` Eli Zaretskii
2020-07-17 16:20 ` Stefan Monnier [this message]
2020-07-17 20:19 ` Zach Shaftel
2020-07-17 22:08 ` Stefan Monnier
2020-07-18 21:41 ` Zach Shaftel
2020-07-19 2:34 ` Stefan Monnier
2020-07-21 0:28 ` Zach Shaftel
2020-07-21 2:51 ` Stefan Monnier
2020-07-16 7:25 ` Andrea Corallo via Emacs development discussions.
2020-07-17 0:24 ` Zach Shaftel
2020-07-17 13:47 ` Rocky Bernstein
2020-07-28 19:19 ` Update 2 " Zach Shaftel
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