powerpc: Enable ARCH_USE_BUILTIN_BSWAP
authorDavid Woodhouse <dwmw2@infradead.org>
Wed, 19 Dec 2012 15:14:17 +0000 (15:14 +0000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Thu, 10 Jan 2013 06:00:54 +0000 (17:00 +1100)
commitfe3955cb297290b0d5dedf5d2694a7cef455010e
tree8901f2f72857d3490c1dda22dcdc3b2d7ccef326
parente49f1e203f3a66dd2982bcd8695e6f4a4f89f876
powerpc: Enable ARCH_USE_BUILTIN_BSWAP

By using the compiler intrinsics instead of hand-crafted opaque inline
assembler for byte-swapping, we let the compiler see what's actually
happening and it gets to use lwbrx/stwbrx instructions instead of a
normal load/store coupled with a sequence of rlwimi instructions to
move bits around.

Compiled-tested only. It gave a code size reduction of almost 4% for
ext2, and more like 2.5% for ext3/ext4.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
arch/powerpc/Kconfig