bug#42147: 28.0.50; pure vs side-effect-free, missing optimizations?

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Sat, 4 Jul 2020 22:25:55 +0000
> Cc: mattiase@acm.org, Paul Eggert <eggert@cs.ucla.edu>, 
> andrea_corallo@yahoo.it,
>  42147@debbugs.gnu.org
> 
> > I'm actually not completely sure why we care about those minor
> > rounding differences.
> 
> Neither am I. If the idea is to standardize Emacs on a single
> floating-point representation, let's at least use the 61-bit floats
> Paul suggested a while back? (Incidentally, I believe those can be
> implemented somewhat more efficiently on x87 hardware). Or we could go
> with bignum ratios or GMP floats.

Some other relevant questions:

  . why didn't GCC folks made SSE2 the default output?  shouldn't
    Emacs follow the defaults, and leave it to the experts to decide
    which instruction set should be the default?

  . which other projects use this non-standard instruction set?  GNU
    Guile, for example, doesn't, so why should we?