Re: Q: What is default architecture for code produced by native compiler?

[Arthur Miller]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Arthur Miller <arthur.miller@live.com>
>> Date: Wed, 25 Aug 2021 03:13:49 +0200
>> Cc: emacs-devel@gnu.org
>> 
>> >> If it is generic, do we have option to pass in arch and cpu flags?
>> >
>> > No we don't, even if we could expose it using
>> > 'gcc_jit_context_add_command_line_option' for non obsolete versions of
>> > GCC.
>> 
>> Allright, is there any interest to expose this? :-)
>> 
>> We could have a defcustom in comp.el, either some boolean like:
>> "native-comp-prefer-host-cpu"
>
> What's wrong with using native-comp-driver-options?
>
> I'm also curious why you want to mess with that.  Do you use the
> equivalent GCC switches when compiling Emacs?  If so, why?
Yes, I do, I compile Emacs with -O3 -march=native and -mcpu=native

Hopefully gcc will emit some AVX instructions where possible. I haven't
dissasembled Emacs binary so I don't know how big is difference between generic
and native.

>> To be honest, I have no idea if there is much if anything to win in speed in 
>> elisp context,
>> between generic and skylake
>
> My guess would be nothing.

Probably. Depends on the problem and data I guess.