bug#65491: [PATCH] Improve performance allocating vectors

[Eli Zaretskii]

> From: Mattias Engdegård <mattias.engdegard@gmail.com>
> Date: Sat, 16 Sep 2023 18:54:27 +0200
> Cc: 65491@debbugs.gnu.org,
>  monnier@iro.umontreal.ca
> 
> 16 sep. 2023 kl. 18.32 skrev Mattias Engdegård <mattias.engdegard@gmail.com>:
> 
> > #define XUNTAG(a, type, ctype) \
> >  ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t)LISP_WORD_TAG (type)))
> 
> I pushed this to master after some experiments.

Sorry, I cannot accept this kind of "discussions" when such tricky
issues come up.  What's the rush of installing changes when you still
didn't answer my questions, and we still are not sure these changes
are correct?  We are touching the deepest bowels of the
implementation, so some caution, even trepidation, is in order.

So I've reverted the last two changes.  Let's finish discussing the
need for this change and why you think the last variant is TRT, and
install then whatever we decide is needed.

I also added Paul to the discussion, since he wrote most of the
involved macros.