Commit 83a57a4d authored Dec 20, 2012 by David Woodhouse Committed by H. Peter Anvin Jan 28, 2013

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: David Woodhouse <David.Woodhouse@intel.com>
Link: http://lkml.kernel.org/r/1355966180.18919.102.camel@shinybook.infradead.org


Signed-off-by: H. 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

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