[PATCH 2/4] powerpc: enable ARCH_USE_BUILTIN_BSWAP

David Woodhouse dwmw2 at infradead.org
Tue Dec 4 21:15:28 EST 2012

From: David Woodhouse <David.Woodhouse at intel.com>

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 at intel.com>
 arch/powerpc/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a902a5c..b4ea516 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -78,6 +78,9 @@ config ARCH_HAS_ILOG2_U64
 	default y if 64BIT
+       def_bool y
 	default y

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