Sorry, I meant: it only improves compilation with -Og _and -O0_. I
don't know if -O0 is important.
Given my measurements (see upthread), the effect on -O0 build is
negligible. And yes, -O0 _is_ important.
I don't know what happens on your computer (what is your
platform/compiler?) but on mine (Debian GNU/Linux with the latest Linux
kernel and the latest GCC) the effect on -O0 is almost the same as on
-Og for this particular benchmark. I just tried again on the emacs-27
branch:
-Og: ~67s
-O0: ~63s
-O1: ~26s
-O2: ~18s
-O3: ~17s