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

[Eli Zaretskii <eliz@gnu.org>]

> 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.