Add configuration for gccemacs (native-comp, emacs28 only)

configuration.org

@@ -8,6 +8,24 @@ Some of my configuration entries where borrowed from other people, see
 
 * Performances tweaks (part. 1, start)
 
+  I am currently experimenting with Emacs 28 and, specifically,
+  GccEmacs that compiles elisp to native binaries. To compile emacs28
+  to macOs (until it is released):
+
+  1. Clone [[https://github.com/jimeh/build-emacs-for-macos][build-emacs-for-macos]]
+  2. Install build dependencies with =brew bundle install= in the cloned folder
+  3. run =./build-emacs-for-macos feature/native-comp=
+  4. The =Emacs.app= will be available in an archive in the =builds=
+     folder
+
+  This sets gcc optimization flag to =-O2= (max optimization level,
+  fully adherent to the langage semantic).
+#+begin_src emacs-lisp
+(unless (version< emacs-version "28"))
+(setq comp-speed 2)
+)
+#+end_src
+
   Decrease the GC frequency by setting the threshold high for
   configuration loading. The threshold will be set lower at the end of
   the configuration to make each GC call faster for normal emacs use.