Re: [RFC] [PATCH] Introduce configure flag --with-stage1-cflags.

[Richard Biener <richard.guenther@gmail.com>]

On Fri, May 26, 2017 at 1:51 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, May 26, 2017 at 01:46:47PM +0200, Richard Biener wrote:
>> On Thu, May 25, 2017 at 11:23 AM, Martin Liška <mliska@suse.cz> wrote:
>> > Hello.
>> >
>> > After a discussion with Richi, using adding "-O2" to STAGE1 cflags with a recent
>> > enough compiler can significantly speed up bootstrap. Thus I'm suggesting to
>> > introduce --with-stage1-cflags where one can provide such options.
>>
>> I don't think this is necessary -- you can always override with STAGE1_CFLAGS.
>>
>> > Apart from that, maybe it would be handy to automatically enable "-O2" when
>> > one has a recent compiler? Do we have an example where we detect host compiler
>> > and it's version?
>>
>> Don't know about version but configury already detects that we use GCC, so that
>> knowledge should be readily available.
>
> Well, it certainly shouldn't be -O2 by default for any system GCC, more
> something like if it is major of the configured configure minus 1 or newer
> (or minus 2?), then use -O2, otherwise default to -O0 as before.

I'd still default to -O0 on release branches regardless of version and then
for development we can probably simply use "any GCC" when people have
the chance to override.

At least for me host GCC 4.8 works quite well with -O2.

Richard.

>         Jakub