From 69237f94e65d3d7f539f1adb98ef68685c595004 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 3 Jul 2009 13:26:41 +0200 Subject: [PATCH] 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 Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: David Howells Cc: Andrew Morton Cc: Arnd Bergmann LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/lib/atomic64_32.c | 19 +++++++------------ 1 file 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; } -- 2.20.1