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x86: atomic64: Improve cmpxchg8b()

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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>
This commit is contained in:
Eric Dumazet 2009-07-03 13:26:41 +02:00 committed by Ingo Molnar
parent aacf682fd8
commit 69237f94e6
1 changed files with 7 additions and 12 deletions
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19
arch/x86/lib/atomic64_32.c
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@ -6,19 +6,14 @@
static inline u64 cmpxchg8b(u64 *ptr, u64 old, u64 new)
{
u32 low = new;
u32 high = new >> 32;
asm volatile(
LOCK_PREFIX "cmpxchg8b (%[ptr])\n"
: "=A" (old)
: [ptr] "D" (ptr),
"A" (old),
"b" (ll_low(new)),
"c" (ll_high(new))
: "memory");
LOCK_PREFIX "cmpxchg8b %1\n"
: "+A" (old), "+m" (*ptr)
: "b" (low), "c" (high)
);
return old;
}