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Commit 83a57a4d authored by David Woodhouse's avatar David Woodhouse Committed by H. Peter Anvin
Browse files

x86: Enable ARCH_USE_BUILTIN_BSWAP 



With -mmovbe enabled (implicit with -march=atom), this allows the
compiler to use the movbe instruction. This doesn't have a significant
effect on code size (unlike on PowerPC), because the movbe instruction
actually takes as many bytes to encode as a simple mov and a bswap. But
for Atom in particular I believe it should give a performance win over
the mov+bswap alternative. That was kind of why movbe was invented in
the first place, after all...

I've done basic functionality testing with IPv6 and Legacy IP, but no
performance testing. The EFI firmware on my test box unfortunately no
longer starts up.

Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
Link: http://lkml.kernel.org/r/1355966180.18919.102.camel@shinybook.infradead.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent f317820c

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ config X86 
	select MODULES_USE_ELF_RELA if X86_64

	select CLONE_BACKWARDS if X86_32

	select GENERIC_SIGALTSTACK

	select ARCH_USE_BUILTIN_BSWAP



config INSTRUCTION_DECODER

	def_bool y