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| author | Jan Beulich <JBeulich@suse.com> | 2012-01-20 20:22:04 +0400 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2012-01-21 05:29:49 +0400 |
| commit | cb8095bba6d24118135a5683a956f4f4fb5f17bb (patch) | |
| tree | 25eff3732e8471e314591d0bc6ea41d96857c18b /arch/x86/include/asm/atomic64_32.h | |
| parent | 819165fb34b9777f852429f2c6d6f79fbb71b9eb (diff) | |
| download | linux-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.h | 5 |
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; } |