Re: Improving EQ

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 12 Dec 2024 08:36:50 +0000
> From: Pip Cet <pipcet@protonmail.com>
> Cc: Mattias Engdegård <mattiase@acm.org>, Paul Eggert <eggert@cs.ucla.edu>, emacs-devel@gnu.org
> 
> "Eli Zaretskii" <eliz@gnu.org> writes:
> 
> > The usual easy benchmark is to byte-compile all the *.el files in the
> > source tree.  That is, remove all the *.elc files, then say "make" and
> > time that.
> 
> Considering the point of the optimization was to make compilation (when
> symbols_with_pos_enabled is true) slower, but speed up non-compilation
> use cases, I think that may be the opposite of what we want :-)

That's fine, because knowing where this slows us down and by how much
is also important.

> Furthermore, the master branch doesn't currently build after deleting
> all the *.elc files, because recompilation exceeds max-lisp-eval-depth
> in that scenario (together with the known purespace issue, this pretty
> much means "make bootstrap" is the only way I can rebuild an emacs tree
> right now. It'd be great if Someone could look into this, but I've
> failed to understand the native-compilation code (and been told off for
> trying to) too often for that Someone to be me. Plus, of course, I fully
> understand that native compilation currently has wrong code generation
> bugs which obviously have to take priority over build issues...)

If this is with native-compilation, how about trying without?

Also, enlarging max-lisp-eval-depth (assuming you don't somehow hit
infinite recursion) locally should be easy: just add that to the
relevant Makefiles.

> https://elpa.gnu.org/packages/elisp-benchmarks.html ? It'd be great if
> we could agree on a benchmark, and even better if there were a way to
> reliably run it from emacs -Q :-)

Our benchmark facilities are very rudimentary, so agreement is not an
issue: we just use whatever is available.

> In fact, I would suggest to move a reduced benchmark suite to the emacs
> repo itself, and run it using "make benchmark".

Working on a better benchmark is very useful, but maybe we should try
solving one problem at a time?

> Also, just to let everyone know, I'm planning to make the "exotic"
> property (this object must or can use the slow_eq path) part (probably
> the LSB) of the tag rather than accessing it via a global variable and
> the PVEC type. This should reduce code size further, should speed up
> things, and has some other advantages which I'll go into when I have
> working code.

Whenever you change something in the tags, please remember to update
.gdbinit, otherwise we lose debugging support.