[PATCH] D126250: [CodeGen][AArch64] Add support for LDAPR

[Kyrill Tkachov via Phabricator via llvm-commits]

ktkachov added a comment.

We've had some back-and-forth on this offline...
We expect the relaxation of the acquire semantics to be correct with this patch, but this has not been proven within the language-to-AArch64 memory model semantics yet.
Some initial testing with the Telechat tool by @LukeGeeson hasn't shown any bad reorderings, which is a good sign.
However, this is a relaxation of ordering constraints, new reorder behaviours can occur. We have kicked off a discussion with our Arm memory model experts to construct a proof that these relaxations at the AArch64 memory model level are allowed by the C/C++/LLVM level. We expect to have such a proof in time for the LLVM 15 release (hopefully sooner, by August).

In the meantime, I'd appreciate it if this behaviour is guarded by a default-off option for now, that can be used for wider internal testing. Once we have proof that this is a correct change we can remove the option, or make it default-on.
Does this approach work for you folks?


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D126250