From cb8095bba6d24118135a5683a956f4f4fb5f17bb Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 20 Jan 2012 16:22:04 +0000 Subject: [PATCH] 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 Link: http://lkml.kernel.org/r/4F19A2BC020000780006E0DC@nat28.tlf.novell.com Cc: Luca Barbieri Cc: Eric Dumazet Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/atomic64_32.h | 5 ++--- arch/x86/lib/atomic64_386_32.S | 6 +++--- arch/x86/lib/atomic64_cx8_32.S | 29 +++++++++++------------------ 3 files changed, 16 insertions(+), 24 deletions(-) diff --git a/arch/x86/include/asm/atomic64_32.h b/arch/x86/include/asm/atomic64_32.h index 908303f..1981199 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; } diff --git a/arch/x86/lib/atomic64_386_32.S b/arch/x86/lib/atomic64_386_32.S index e8e7e0d..00933d5 100644 --- a/arch/x86/lib/atomic64_386_32.S +++ b/arch/x86/lib/atomic64_386_32.S @@ -137,13 +137,13 @@ BEGIN(dec_return) RET_ENDP #undef v -#define v %ecx +#define v %esi BEGIN(add_unless) - addl %eax, %esi + addl %eax, %ecx adcl %edx, %edi addl (v), %eax adcl 4(v), %edx - cmpl %eax, %esi + cmpl %eax, %ecx je 3f 1: movl %eax, (v) diff --git a/arch/x86/lib/atomic64_cx8_32.S b/arch/x86/lib/atomic64_cx8_32.S index 391a083..f5cc9eb 100644 --- a/arch/x86/lib/atomic64_cx8_32.S +++ b/arch/x86/lib/atomic64_cx8_32.S @@ -55,8 +55,6 @@ ENDPROC(atomic64_set_cx8) ENTRY(atomic64_xchg_cx8) CFI_STARTPROC - movl %ebx, %eax - movl %ecx, %edx 1: LOCK_PREFIX cmpxchg8b (%esi) @@ -78,7 +76,7 @@ ENTRY(atomic64_\func\()_return_cx8) movl %edx, %edi movl %ecx, %ebp - read64 %ebp + read64 %ecx 1: movl %eax, %ebx movl %edx, %ecx @@ -159,23 +157,22 @@ ENTRY(atomic64_add_unless_cx8) SAVE ebx /* these just push these two parameters on the stack */ SAVE edi - SAVE esi + SAVE ecx - movl %ecx, %ebp - movl %eax, %esi + movl %eax, %ebp movl %edx, %edi - read64 %ebp + read64 %esi 1: cmpl %eax, 0(%esp) je 4f 2: movl %eax, %ebx movl %edx, %ecx - addl %esi, %ebx + addl %ebp, %ebx adcl %edi, %ecx LOCK_PREFIX - cmpxchg8b (%ebp) + cmpxchg8b (%esi) jne 1b movl $1, %eax @@ -199,13 +196,13 @@ ENTRY(atomic64_inc_not_zero_cx8) read64 %esi 1: - testl %eax, %eax - je 4f -2: + movl %eax, %ecx + orl %edx, %ecx + jz 3f movl %eax, %ebx - movl %edx, %ecx + xorl %ecx, %ecx addl $1, %ebx - adcl $0, %ecx + adcl %edx, %ecx LOCK_PREFIX cmpxchg8b (%esi) jne 1b @@ -214,9 +211,5 @@ ENTRY(atomic64_inc_not_zero_cx8) 3: RESTORE ebx ret -4: - testl %edx, %edx - jne 2b - jmp 3b CFI_ENDPROC ENDPROC(atomic64_inc_not_zero_cx8) -- 2.7.4