[tip:perfcounters/urgent] x86: atomic64: Improve cmpxchg8b()
From: tip-bot for Eric Dumazet
Date: Fri Jul 03 2009 - 08:45:29 EST
Commit-ID: 69237f94e65d3d7f539f1adb98ef68685c595004
Gitweb: http://git.kernel.org/tip/69237f94e65d3d7f539f1adb98ef68685c595004
Author: Eric Dumazet <eric.dumazet@xxxxxxxxx>
AuthorDate: Fri, 3 Jul 2009 13:26:41 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Fri, 3 Jul 2009 13:26:41 +0200
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@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/x86/lib/atomic64_32.c | 19 +++++++------------
1 files changed, 7 insertions(+), 12 deletions(-)
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c
index afa5d44..5fc1e2c 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;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/