Re: The Emacs master is much slower than the emacs-27 branch.

[Óscar Fuentes]

martin rudalics <rudalics@gmx.at> writes:

>> 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
>
> So when I want to compare Emacs 27 and Emacs 28 benchmarks, -Og builds
> are off limits.  Now can I use O0 builds or do I have to use O1-O3
> builds exclusively?

-Og is the recommended setting for the edit/build/debug cycle [1],
because it *improves* debug info accuracy over -O0 *and* also runs
faster, which is a significant bonus. So IMHO it is a good thing to not
regress -Og too much. -O0, on the other hand, shouldn't be a concern.

1. https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html