RFR: 8261579: AArch64: Support for weaker memory ordering in Atomic [v6]

[Aleksey Shipilev]

On Mon, 28 Jun 2021 16:21:50 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> At present the Atomic operations in HotSpot only support conservative (the very strongest) and relaxed (the weakest) memory ordering.
>> We should add at least seq_cst for LSE. This patch also adds a release-only CAS, needed for Shenandoah.
>
> Andrew Haley has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 16 additional commits since the last revision:
> 
>  - Merge branch 'master' into aarch64_acq_rel_cas
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.S
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.hpp
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.hpp
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - Update src/hotspot/cpu/aarch64/atomic_aarch64.hpp
>    
>    Co-authored-by: Aleksey Shipilëv <shade at redhat.com>
>  - ... and 6 more: https://git.openjdk.java.net/jdk/compare/9759b6e0...e2327629

Performance data looks good, I think it does what it should.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4597