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

[Martin Liška]

On 05/26/2017 01:55 PM, Richard Biener wrote:
> 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.

Ok, sending new patch that does that on experimental branches for ${CC} --version
being a GCC newer than 4.9.

Martin

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

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