On Wed, Aug 18, 2010, Carsten Munk wrote: > Compile Qt with NEON support by default on ARMv7. Include script in > startup that provides QT_NO_NEON=1 to the UX session based on NEON > presence in /proc/cpuinfo.
"Compile Qt with NEON support by default" scares me. One thing to be careful about is to turn on -mfpu=neon ONLY when building files with functions which use NEON. Do NOT call any of the functions in these files unless you checked for NEON in /proc/self/auxv before hand. If you simply turn on NEON for all of Qt, then the toolchain might decide using it pretty much anywhere, either now, or in a toolchain update. Hwcaps is an easier way to provide a NEON and a regular version of libQt.so libs, simply build the whole lib with -mfpu=neon and put it in /usr/lib/neon/vfp. I wouldn't recommend hwcaps if you can implement runtime detection instead, since this means you either have to ship two copies of the Qt libs (and that's not negligible) or that you have to split them in two packages, and dependencies on the Qt packages become a nightmare. Someone helpfully pointed at /proc/self/auxv in this thread; this is the right interface on Linux, but it's not portable, and I think Qt aims at being quite portable, so you might want to ALSO support SIGILL and environment vars as well for other platforms (BSDs, other UNIXes etc.). -- Loïc Minier _______________________________________________ MeeGo-dev mailing list [email protected] http://lists.meego.com/listinfo/meego-dev
