[Development] QTBUG-30440: restricting the SIMD files

Thiago Macieira thiago.macieira at intel.com
Fri Aug 16 17:46:16 CEST 2013

On sexta-feira, 16 de agosto de 2013 11:53:45, Koehne Kai wrote:
> > I recommend:
> >       CFLAGS (x86) = -march=i686 -mtune=core2 -msse2 -mfpmath=sse
> >       CFLAGS (x86-64) = -mtune=core2
> >       LFLAGS = -Wl,-O1 -Wl,--as-needed -Wl,-z,relro
> >
> > 
> >
> > For MSVC, set CFLAGS on x86 to -arch:SSE2.
> I'm not sure I understand. Do you suggest to update the default mkspec's for
> e.g. linux-g++ in qtbase? Or do you suggest that we compile our binary
> installers with CLAGS set?

I suggest we leave the mkspecs files alone. Don't change them.

Instead, change the build environment for our binaries only, setting the 
environment variables so that the build picks them up.

I know that the Unix configure script does that, but I actually don't know if 
you can set flags using configure.exe.

BTW, if we wanted to supply both sse2 and non-sse2 versions of the libraries, 
we could. We don't, So this is here only for future reference, if a distro or 
someone else wants to do it:

Linux's ld-linux.so.2 on x86 always tries to load a library in a subdir called 
"sse2" if the CPU has SSE2 support. So we could have:
	$libdir/libQt5Core.so.5		no SSE2
	$libdir/sse2/libQt5Core.so.5	SSE2 required

Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
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