Hi, Andres mentioned in passing that he'd defined PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY only on Itanium, PPC and x86 but not ARM.
I took a look at https://developer.arm.com/documentation/ddi0487/gb/ under "B2.2.1 Requirements for single-copy atomicity" and it seemed like we should turn this on for __aarch64__. It goes back to the original ARMv8-A so should cover all 64 bit ARM systems.
From 1721c7b15b132c2aa16b18cf0b3eea054247833d Mon Sep 17 00:00:00 2001 From: Thomas Munro <thomas.mu...@gmail.com> Date: Wed, 3 Nov 2021 10:23:33 +1300 Subject: [PATCH] AArch64 has single-copy 64 bit atomicity. This avoids using more expensive atomic operations when plain loads and stores would do. --- src/include/port/atomics/arch-arm.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/src/include/port/atomics/arch-arm.h b/src/include/port/atomics/arch-arm.h index efa385321e..a5b84baa71 100644 --- a/src/include/port/atomics/arch-arm.h +++ b/src/include/port/atomics/arch-arm.h @@ -24,3 +24,8 @@ #if !defined(__aarch64__) && !defined(__aarch64) #define PG_DISABLE_64_BIT_ATOMICS #endif /* __aarch64__ || __aarch64 */ + +#if defined(__aarch64__) +/* per architecture manual doubleword accesses have single copy atomicity */ +#define PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY +#endif -- 2.25.1
