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authorEric Dumazet <eric.dumazet@gmail.com>2009-07-03 13:26:41 +0200
committerIngo Molnar <mingo@elte.hu>2009-07-03 13:26:41 +0200
commit69237f94e65d3d7f539f1adb98ef68685c595004 (patch)
treebe7f8e2b323206bc10f82ca5a70ed5cf646c4fb9 /arch
parentx86: atomic64: Improve atomic64_read() (diff)
downloadlinux-69237f94e65d3d7f539f1adb98ef68685c595004.tar.xz
linux-69237f94e65d3d7f539f1adb98ef68685c595004.zip
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/lib/atomic64_32.c19
1 files changed, 7 insertions, 12 deletions
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c
index afa5d444918b..5fc1e2caa544 100644
--- a/arch/x86/lib/atomic64_32.c
+++ b/arch/x86/lib/atomic64_32.c
@@ -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;
}