From c2df0a6af177b6c06a859806a876f92b072dc624 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Sun, 15 May 2022 20:42:04 +0200 Subject: locking/atomic/x86: Introduce arch_try_cmpxchg64 Introduce arch_try_cmpxchg64 for 64-bit and 32-bit targets to improve code using cmpxchg64. On 64-bit targets, the generated assembly improves from: ab: 89 c8 mov %ecx,%eax ad: 48 89 4c 24 60 mov %rcx,0x60(%rsp) b2: 83 e0 fd and $0xfffffffd,%eax b5: 89 54 24 64 mov %edx,0x64(%rsp) b9: 88 44 24 60 mov %al,0x60(%rsp) bd: 48 89 c8 mov %rcx,%rax c0: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) c5: 48 8b 74 24 60 mov 0x60(%rsp),%rsi ca: f0 49 0f b1 34 24 lock cmpxchg %rsi,(%r12) d0: 48 39 c1 cmp %rax,%rcx d3: 75 cf jne a4 to: b3: 89 c2 mov %eax,%edx b5: 48 89 44 24 60 mov %rax,0x60(%rsp) ba: 83 e2 fd and $0xfffffffd,%edx bd: 89 4c 24 64 mov %ecx,0x64(%rsp) c1: 88 54 24 60 mov %dl,0x60(%rsp) c5: c6 44 24 62 f2 movb $0xf2,0x62(%rsp) ca: 48 8b 54 24 60 mov 0x60(%rsp),%rdx cf: f0 48 0f b1 13 lock cmpxchg %rdx,(%rbx) d4: 75 d5 jne ab where a move and a compare after cmpxchg is saved. The improvements for 32-bit targets are even more noticeable, because dual-word compare after cmpxchg8b gets eliminated. Signed-off-by: Uros Bizjak Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220515184205.103089-3-ubizjak@gmail.com --- arch/x86/include/asm/cmpxchg_64.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'arch/x86/include/asm/cmpxchg_64.h') diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h index 072e5459fe2f..250187ac8248 100644 --- a/arch/x86/include/asm/cmpxchg_64.h +++ b/arch/x86/include/asm/cmpxchg_64.h @@ -19,6 +19,12 @@ static inline void set_64bit(volatile u64 *ptr, u64 val) arch_cmpxchg_local((ptr), (o), (n)); \ }) +#define arch_try_cmpxchg64(ptr, po, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_try_cmpxchg((ptr), (po), (n)); \ +}) + #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16) #endif /* _ASM_X86_CMPXCHG_64_H */ -- cgit v1.2.3