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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>
This commit is contained in:
David Woodhouse 2012-12-19 15:14:17 +00:00 committed by Benjamin Herrenschmidt
parent e49f1e203f
commit fe3955cb29
1 changed files with 1 additions and 0 deletions
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arch/powerpc/Kconfig
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@ -144,6 +144,7 @@ config PPC
select HAVE_MOD_ARCH_SPECIFIC
select MODULES_USE_ELF_RELA
select CLONE_BACKWARDS
select ARCH_USE_BUILTIN_BSWAP
config EARLY_PRINTK
bool