[bug#38619] Byte compilation of Emacs autoloads

[Maxim Cournoyer]

Hello,

The following adds support for byte compiling the generated autoload
files as well as the site-lisp directory of Emacs (the one containing
the site-start.el and guix-emacs.el files).

The performance gain is roughly 30%, as expected for byte compiled
Elisp.  The following command was used for benchmarking:

--8<---------------cut here---------------start------------->8---
./pre-inst-env guix environment -v 10 -m ~/100-emacs-packages-manifest.scm -- 
emacs -Q --batch --eval "(progn (require 'guix-emacs) (message \"%s\" 
(benchmark-run-compiled 10 (guix-emacs-autoload-packages))))"
--8<---------------cut here---------------end--------------->8---

It loads the autoloads of ~100 Emacs packages 10 times (~1000 autoloads
files).  The manifest file 100-emacs-packages-manifest.scm is attached.

100-emacs-packages-manifest.scm
Description: Binary data

The above command for Guix before the changes (commit e19a539):

--8<---------------cut here---------------start------------->8---
[...]
Loading 
/gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/undercover-autoloads.el
 (source)...
Loading 
/gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/with-editor-autoloads.el
 (source)...
Loading 
/gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/ws-butler-autoloads.el
 (source)...
Loading 
/gnu/store/lj09yx56hgsq9l4ajk5wlxsk4vbrympk-profile/share/emacs/site-lisp/yasnippet-autoloads.el
 (source)...
(9.971024566 159 2.763721703999999)
--8<---------------cut here---------------end--------------->8---

After the changes:

--8<---------------cut here---------------start------------->8---
Loading 
/gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/undercover-autoloads...
Loading 
/gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/with-editor-autoloads...
Loading 
/gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/ws-butler-autoloads...
Loading 
/gnu/store/fwji52vg31xmdkc2z5cbjrfza7fxndr5-profile/share/emacs/site-lisp/yasnippet-autoloads...
(7.435941036 143 2.406266451999999)
--8<---------------cut here---------------end--------------->8---

I think it's neat that all of our Elisp is byte compiled; it's something
that can be done without fear on Guix, given that when the Emacs package itself
changes, all the Emacs packages are rebuilt.  It could also find issues we'd not
know existed otherwise, as I found out for the emacs-cl-generic package.

0001-gnu-emacs-Byte-compile-the-site-lisp-directory.patch
Description: Text Data

0002-emacs-build-system-Byte-compile-the-autoload-files.patch
Description: Text Data

0003-gnu-emacs-cl-generic-Disable-byte-compilation-of-its.patch
Description: Text Data

Maxim