bug#69314: [PATCH] Speed up stage0 bootstrap build using prebuilts

On Mon, 2024-05-06 at 11:34 +0200, Ludovic Courtès wrote:
> Hi Jonas,
> 
> Jonas Hahnfeld <[email protected]> skribis:
> 
> > On Thu, 2024-01-04 at 11:57 +0100, Jonas Hahnfeld wrote:
> > > From 95f15821c535537c7ad4fdae1988855314d56ece Mon Sep 17 00:00:00 2001
> > > From: Jonas Hahnfeld <[email protected]>
> > > Date: Thu, 4 Jan 2024 11:44:55 +0100
> > > Subject: [PATCH] Speed up stage0 bootstrap build using prebuilts
> > > 
> > > Use prebuilt bytecode of ice-9/eval.go and others for all of stage0,
> > > it is optimized and evaluation is much faster. In my environment,
> > > this speeds up the build of guile-3.0.9 from around 29 minutes to
> > > only 19 minutes.
> > > 
> > > * meta/build-env.in: In stage0, prefer prebuilt bytecode over just
> > > compiled stage0 files.
> > > ---
> > >  meta/build-env.in | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/meta/build-env.in b/meta/build-env.in
> > > index bdc88ded4..446a536af 100644
> > > --- a/meta/build-env.in
> > > +++ b/meta/build-env.in
> > > @@ -58,7 +58,7 @@ then
> > >      fi
> > >      export GUILE_LOAD_PATH
> > >      case "$GUILE_BOOTSTRAP_STAGE" in
> > > -        stage0) GUILE_LOAD_COMPILED_PATH="${top_builddir}/stage0:${top_srcdir}/prebuilt/@SCM_PREBUILT_BINARIES@" ;;
> > > +        stage0) GUILE_LOAD_COMPILED_PATH="${top_srcdir}/prebuilt/@SCM_PREBUILT_BINARIES@:${top_builddir}/stage0" ;;
> 
> I don’t understand why changing the order would make a difference.
> Surely if .go files are available under prebuilt/, they’ll be found,
> even if that directory comes second?  Or am I missing something?

Yes, they are found but with lower priority. As I try to explain in the
commit message (could be improved though), the same bytecode is also
built during stage0, but without optimizations which makes the rest of
stage0 awfully slow.

Jonas

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