On Fri, 2022-02-25 at 17:10 +0300, Alexander Monakov via Gcc-help wrote: > > > https://cdrdv2.intel.com/v1/dl/getContent/671294 TL;DR: Intel says on their CPUs with AVX, 128-bit loads (with movdqa) are atomic, see page 393 of this doc. And this is updated in Dec 2021, so you may need to re-download the Intel SDM to get a latest copy. > > > Create an issue in bugzilla then? > > > > Yes please. I should have read the whole thread first. 8-) > > > > The AMD manual doesn't say this yet, so any optimization needs to be > > restricted to Intel CPUs for now. I'll reach out to AMD to get > > clarification. > > This StackOverflow question has evidence that both Intel (Core Duo) > and > AMD (Opteron 2435) can tear 128-bit loads. Core Duo does not have AVX, and AMD has not make any guarantee for the atomicity of 128-bit load. So we can't use movdqa for 128-bit atomics on those old Intel and (old or new) AMD models. > So neither manufacturer can > give a retroactive guarantee. > > https://stackoverflow.com/questions/7646018/sse-instructions-which-cpus-can-do-atomic-16b-memory-operations > > Alexander -- Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University
