[Development] Updating x86 SIMD support in Qt

Thiago Macieira thiago.macieira at intel.com
Wed Jan 19 20:07:41 CET 2022


On Wednesday, 19 January 2022 09:51:38 PST Alexandru Croitor wrote:
> > On 19. Jan 2022, at 18:34, Thiago Macieira <thiago.macieira at intel.com>
> > wrote:
> > 
> > Indeed. I'm hoping it's a matter of making qt_internal_add_module()
> > creating two CMake targets instead of one, and modifying the C and C++
> > compiler flags as well as output dir for one of them.
> 
> Which library names appear in the dynamic section of v3/v4 libraries, as
> reported by readelf -d? Is it the original non-suffixed v2 library? Put
> differently, when building the v4 version of QtGui, does it need to link to
> QtCore-v4 or QtCore? 

They should link to the baseline, whatever the baseline the user chose to be. 
In fact, the "libQt6Xxxx.so" symlink only needs to exist at the top-dir 
because the regular linker doesn't search the subdirs. So it's actually 
important that both binaries have the same ABI and export the same functions, 
even if they wouldn't be used by a matching build. I made this mistake in 
Clear Linux by suppressing the qfloat16 tables in the AVX2 build.

If you install my libqt5-qtbase RPMs for OpenSUSE, you get:

/usr/lib64/haswell/libQt5Core.so.5@
/usr/lib64/haswell/libQt5Core.so.5.15@
/usr/lib64/haswell/libQt5Core.so.5.15.2
/usr/lib64/haswell/libQt5Gui.so.5@
/usr/lib64/haswell/libQt5Gui.so.5.15@
/usr/lib64/haswell/libQt5Gui.so.5.15.2
/usr/lib64/libQt5Core.prl
/usr/lib64/libQt5Core.so@
/usr/lib64/libQt5Core.so.5@
/usr/lib64/libQt5Core.so.5.15@
/usr/lib64/libQt5Core.so.5.15.2
/usr/lib64/libQt5Gui.prl
/usr/lib64/libQt5Gui.so@
/usr/lib64/libQt5Gui.so.5@
/usr/lib64/libQt5Gui.so.5.15@
/usr/lib64/libQt5Gui.so.5.15.2
/usr/lib64/pkgconfig/Qt5Core.pc
/usr/lib64/pkgconfig/Qt5Gui.pc

@ are symlinks. I didn't include the CMake files in the paste, but they are 
like prl and pc files.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel DPG Cloud Engineering





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