[Development] QTBUG-30440: restricting the SIMD files

[Koehne Kai]

> -----Original Message-----
> From: development-bounces+kai.koehne=digia.com at qt-project.org
> [mailto:development-bounces+kai.koehne=digia.com at qt-project.org] On
> Behalf Of Thiago Macieira
> Sent: Monday, August 19, 2013 9:42 AM
> To: development at qt-project.org
> Subject: Re: [Development] QTBUG-30440: restricting the SIMD files
> 
> On segunda-feira, 19 de agosto de 2013 07:37:58, Koehne Kai wrote:
> > I don't know how big the performance gains really are, but if it's
> > noticeable, why not switch the default for everyone using the default
> > mkspec?
> 
> Switching the default means making it difficult to unset for those who want it
> unset.

Well, it's just copying /editing the mkspec ... Arguably not the most obvious way to do it, but maybe we should just document it a bit better, then :)

> We recommend people set the environment if they want different flags,
> besides the stock from their compilers. 

Where do we recommend this? E.g.

http://qt-project.org/doc/qt-5.0/qtdoc/install-x11.html

just says to run configure ... Actually it doesn't look like CFLAGS, LFLAGS is mentioned anywhere in the Qt documentation.

> If we recommend that, why not use
> that ourselves?

Well, I just think most people compiling on their own will miss this optimization then. If we think it's a useful optimization that helps >95% of our customers, it should IMO be the default . If not, I'm not sure we should apply it to our binary installers either.

Regards

Kai