[kde-freebsd] Fixing devel/qt4-corelib to build with clang

[Raphael Kubo da Costa]

Dimitry Andric <dimitry at andric.com> writes:

> And it does similar includes for other intrinsics.  Note that it tests
> both QT_HAVE_SSE3 (which is a configure-time feature), and __SSE3__,
> which is defined by the compiler, if it supports SSE3 in the current
> mode.  That is, if you either pass -msse3 on the command line, or use a
> -march= or -mcpu= setting which is high enough to support the SSE3
> feature.

Related question: do you know why versions of GCC which do support those
CPU instructions work in i386/i486 without any additional flags?

This whole issue got me really curious, and after installing a Debian
i386 virtual machine to build a file which just includes
<mm3dnow.h>. Both GCC 4.6 and 4.7 build it fine regardless of the values
I pass to -march (or if I don't pass any value at all), whereas clang 3.0
works by default but fails with those errors you mentioned if I pass
-march={i386,i486,etc}.