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authorJan Beulich <JBeulich@suse.com>2012-01-20 20:22:04 +0400
committerH. Peter Anvin <hpa@linux.intel.com>2012-01-21 05:29:49 +0400
commitcb8095bba6d24118135a5683a956f4f4fb5f17bb (patch)
tree25eff3732e8471e314591d0bc6ea41d96857c18b /arch/x86/include/asm/atomic64_32.h
parent819165fb34b9777f852429f2c6d6f79fbb71b9eb (diff)
downloadlinux-cb8095bba6d24118135a5683a956f4f4fb5f17bb.tar.xz
x86: atomic64 assembly improvements
In the "xchg" implementation, %ebx and %ecx don't need to be copied into %eax and %edx respectively (this is only necessary when desiring to only read the stored value). In the "add_unless" implementation, swapping the use of %ecx and %esi for passing arguments allows %esi to become an input only (i.e. permitting the register to be re-used to address the same object without reload). In "{add,sub}_return", doing the initial read64 through the passed in %ecx decreases a register dependency. In "inc_not_zero", a branch can be eliminated by or-ing together the two halves of the current (64-bit) value, and code size can be further reduced by adjusting the arithmetic slightly. v2: Undo the folding of "xchg" and "set". Signed-off-by: Jan Beulich <jbeulich@suse.com> Link: http://lkml.kernel.org/r/4F19A2BC020000780006E0DC@nat28.tlf.novell.com Cc: Luca Barbieri <luca@luca-barbieri.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/include/asm/atomic64_32.h')
-rw-r--r--arch/x86/include/asm/atomic64_32.h5
1 files changed, 2 insertions, 3 deletions
diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h
index 908303f68bba..198119910da5 100644
--- a/arch/x86/include/asm/atomic64_32.h
+++ b/arch/x86/include/asm/atomic64_32.h
@@ -288,9 +288,8 @@ static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
unsigned low = (unsigned)u;
unsigned high = (unsigned)(u >> 32);
alternative_atomic64(add_unless,
- ASM_OUTPUT2("+A" (a), "+c" (v),
- "+S" (low), "+D" (high)),
- ASM_NO_INPUT_CLOBBER("memory"));
+ ASM_OUTPUT2("+A" (a), "+c" (low), "+D" (high)),
+ "S" (v) : "memory");
return (int)a;
}