Re: Time to merge scratch/correct-warning-pos into master, perhaps?

[Alan Mackenzie]

Hello, Eli.

On Sat, Feb 05, 2022 at 10:17:36 +0200, Eli Zaretskii wrote:
> > Date: Fri, 4 Feb 2022 21:24:56 +0000
> > Cc: gregory@heytings.org, monnier@iro.umontreal.ca, mattiase@acm.org,
> >   larsi@gnus.org, emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > > First, are symbols-with-pos supposed to happen in bytecode that
> > > doesn't deal with byte compilation?

> > Symbols with pos are intended to be used only in compilation, native- as
> > well as byte-.  They mustn't be output to .elc files.

> So that would mean the slowdown of EQ is due to the cases where the
> objects are not-EQ?

Yes.

> Where are the numbers that show how much slower is the current EQ, for
> the case of EQ and not-EQ objects?

We don't have any such numbers.  Is it even possible to measure this?  On
earlier processors, we could have just counted up processor cycles used
for each instruction, but not any more.

> > > If yes, why/when would such objects appear in GP bytecode?

> > What does "GP" mean here, please?

> General Purpose.

Thanks.  Symbols with position shouldn't appear at all in general purpose
bytecode.

> > > > > What is there in a symbol-with-pos except the symbol and the position?

> > > > There is the symbol, the position, and a pseudovector header.

> > > The pseudovector part is not needed if we just extend Lisp_Symbol to
> > > have an additional field 'position'.

> > Yes.  I'm not sure we can do this, though.

> Let's revisit that once we understand the slowdown of EQ better and
> more quantitatively.

OK.

-- 
Alan Mackenzie (Nuremberg, Germany).