Messages in this thread | | | From | Alexei Starovoitov <> | Date | Tue, 1 Dec 2020 21:55:22 -0800 | Subject | Re: [PATCH v2 bpf-next 10/13] bpf: Add instructions for atomic[64]_[fetch_]sub |
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On Tue, Dec 1, 2020 at 4:38 AM Brendan Jackman <jackmanb@google.com> wrote: > > I guess it's also worth remembering other archs might have an atomic > subtract.
which one? arm64 LSE implements atomic_fetch_sub as neg+ldadd. imo x64 and arm64 example outweighs choices by other archs if there are such. Even without LSE it will be neg+llsc loop. The reason I proposed bpf xsub insn earlier is that I thought that llvm won't be able to emit it so easily and JIT/verifier would struggle.
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