Re: Speeding up the bootstrap build - a quick hack.

[Alan Mackenzie]

Hello, Eli.

On Tue, Jan 18, 2022 at 21:34:38 +0200, Eli Zaretskii wrote:
> > From: Stefan Monnier <monnier@iro.umontreal.ca>
> > Cc: Alan Mackenzie <acm@muc.de>,  emacs-devel@gnu.org
> > Date: Tue, 18 Jan 2022 13:40:19 -0500

> > > Is this .elc0 trick just to avoid the ELC+ELN compilation of
> > > COMPILE_FIRST, and instead first compile them only to .elc and then
> > > compile again to .elc + .eln?

> > Yes.

> > > If so, why not use no-native-compile to disable the ELN part?  Since
> > > compile-first is called from src/Makefile, as part of building
> > > bootstrap-emacs, you can do that in the commands there.

> > But we also want to native-compile those files (after we've
> > byte-compiled them), so we do need two different targets.

> No, we need two consecutive shell commands under the same target: one
> with no-native-compile set, the other without it.

> This is the current recipe:

>   ifeq ($(DUMPING),pdumper)
>   $(bootstrap_pdmp): bootstrap-emacs$(EXEEXT)
>         rm -f $@
>         $(RUN_TEMACS) --batch $(BUILD_DETAILS) -l loadup --temacs=pbootstrap \
>                 --bin-dest $(BIN_DESTDIR) --eln-dest $(ELN_DESTDIR)
>         @: Compile some files earlier to speed up further compilation.
>         $(MAKE) -C ../lisp compile-first EMACS="$(bootstrap_exe)"
>   endif

> What I had in mind is to run the last "$(MAKE) -C ../lisp compile-first"
> line so that it binds no-native-compile to non-nil, and then is to run
> it again without binding that variable, after touch'ing the corresponding
> *.el files to force the recompile.

> > Those should ideally be `.elc` first and `.eln` later, but we currently
> > don't know how to make that work, so Alan suggests to use `.elc0` first
> > and `.elc` later.

> I know.

This little project started off life quite simple, but has turned
unbelievably complicated in the last few hours.

I'll have a look at what you're written above tomorrow, in the hope that
it will simplify the recipe I've got at the moment.

But the main thing is that it _is_ possible to reduce how long a native
compilation build takes.  Reducing the compilation time of comp.el from
2min 30sec to 1min 20sec I think is worthwhile.

-- 
Alan Mackenzie (Nuremberg, Germany).