From: David Woodhouse Date: Mon, 3 Dec 2012 16:25:40 +0000 (+0000) Subject: byteorder: allow arch to opt to use GCC intrinsics for byteswapping X-Git-Tag: v3.8-rc1~52^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cf66bb93e0f75e0a4ba1ec070692618fa028e994;p=pandora-kernel.git byteorder: allow arch to opt to use GCC intrinsics for byteswapping 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 Acked-by: H. Peter Anvin --- Reading git-diff-tree failed