Commit 69237f94 authored Jul 03, 2009 by Eric Dumazet Committed by Ingo Molnar Jul 03, 2009

x86: atomic64: Improve cmpxchg8b()



Rewrite cmpxchg8b() to not use %edi register but a generic "+m"
constraint, to increase compiler freedom in code generation and
possibly better code.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent aacf682f

arch/x86/lib/atomic64_32.c

+7 −12

Original line number	Diff line number	Diff line
		@@ -6,19 +6,14 @@

		static inline u64 cmpxchg8b(u64 *ptr, u64 old, u64 new)
		{
		asm volatile(

		LOCK_PREFIX "cmpxchg8b (%[ptr])\n"

		: "=A" (old)

		: [ptr] "D" (ptr),
		"A" (old),
		"b" (ll_low(new)),
		"c" (ll_high(new))

		: "memory");
		u32 low = new;
		u32 high = new >> 32;

		asm volatile(
		LOCK_PREFIX "cmpxchg8b %1\n"
		: "+A" (old), "+m" (*ptr)
		: "b" (low), "c" (high)
		);
		return old;
		}