[Development] QTBUG-30440: restricting the SIMD files

Koehne Kai Kai.Koehne at digia.com
Mon Aug 19 09:56:43 CEST 2013

> -----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.


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.



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