Add atomic read-modify-write operations

[matetokodi]

This patch adds atomic read-modify-write operations to the interpreter:

• Atomic Load
• Atomic Store
• Atomic Rmw Add
• Atomic Rmw Sub
• Atomic Rmw And
• Atomic Rmw Or
• Atomic Rmw Xor
• Atomic Rmw Xchg
• Atomic Rmw Cmpxchg

The test included from https://github.com/WebAssembly/threads/blob/main/test/core/atomic.wast currently does not pass, because it includes the following instructions not implemented in this patch:

• memory.atomic.notify
• memory.atomic.wait32
• memory.atomic.wait64
• atomic.fence

Excluding these, all other test cases pass.

[zherczeg]

@clover2123 are you interested in atomic operation support?

[clover2123]

It seems that threads feature is still in draft status. I think that we need to support official wasm release first. For now, release 2.0 is the latest spec (https://webassembly.github.io/spec/core/index.html) Is there any specific reason for implementing atomic operations? And are you going to update JITC support as well?

[zherczeg]

JIT has some atomic support now, and we wanted to try it, but no other reason. It is not important so this work can be postponed.

[clover2123]

IMHO it's better to postpone this patch. We can merge it when it is really required later :)

[zherczeg]

Maybe we should close this issue.