user/sven/linux.git/include/uapi/linux/swab.h, branch v3.9.7Linux Kernel
https://git.stealer.net/cgit.cgi/user/sven/linux.git/atom?h=v3.9.72012-12-06T01:22:31Zbyteorder: allow arch to opt to use GCC intrinsics for byteswapping2012-12-06T01:22:31ZDavid WoodhouseDavid.Woodhouse@intel.com2012-12-03T16:25:40Zurn:sha1:cf66bb93e0f75e0a4ba1ec070692618fa028e994
Since GCC 4.4, there have been __builtin_bswap32() and __builtin_bswap16()
intrinsics. A __builtin_bswap16() came a little later (4.6 for PowerPC,
48 for other platforms).
By using these instead of the inline assembler that most architectures
have in their __arch_swabXX() macros, we let the compiler see what's
actually happening. The resulting code should be at least as good, and
much *better* in the cases where it can be combined with a nearby load
or store, using a load-and-byteswap or store-and-byteswap instruction
(e.g. lwbrx/stwbrx on PowerPC, movbe on Atom).
When GCC is sufficiently recent *and* the architecture opts in to using
the intrinsics by setting CONFIG_ARCH_USE_BUILTIN_BSWAP, they will be
used in preference to the __arch_swabXX() macros. An architecture which
does not set ARCH_USE_BUILTIN_BSWAP will continue to use its own
hand-crafted macros.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
UAPI: (Scripted) Disintegrate include/linux2012-10-13T09:46:48ZDavid Howellsdhowells@redhat.com2012-10-13T09:46:48Zurn:sha1:607ca46e97a1b6594b29647d98a32d545c24bdff
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>