Winch atomic loads x64

[MarinPostma]

this PR enable the thread feature for x64 in Winch, and implements atomic loads. This includes:

• i32.atomic.load8_u
• i32.atomic.load16_u
• i32.atomic.load
• i64.atomic.load8_u
• i64.atomic.load16_u
• i64.atomic.load32_u
• i64.atomic.load

#9734

reopened from #9954 because the branch was wrong

[cfallin]

Rather than a bool, which can be error-prone, could you define a small enum WasmLoadKind { Regular, Atomic } or similar and match on it in this function?

[saulecabrera]

Could you return a proper CodeGenError instead of panicking? I'm in the process of enabling spec tests for aarch64, in general recoverable errors are preferred as it makes it easier to define when a particular proposal is not fully supported in a particular backend (like threads in aarch64)

I believe we have CodeGenError::unimplemented_masm_instruction()

[saulecabrera]

Given this comment and for the purposes of this pull request, I wonder if it's necessary to introduce a new method in the MacroAssembler. I'd prefer if possible, if we could instead extend the current load definition to take in a load_kind argument, which categorizes if the load is atomic or not, similar to Chris' comment in https://github.com/bytecodealliance/wasmtime/pull/9970/files#r1909577300, that would also simplify the indirection happening in the CodeGen module:

We could simplify to:

• Extending emit_wasm_load to take in a load kind
• Performing the right dispatch directly from that method to the MacroAssembler, by passing the in-scope load kind.

[MarinPostma]

sure i'll do that

[MarinPostma]

comments addressed

[MarinPostma]

I'll fix the test tommorow.

[github-actions]

Subscribe to Label Action

cc @saulecabrera

This issue or pull request has been labeled: "wasmtime:api", "wasmtime:config", "winch"

Thus the following users have been cc'd because of the following labels:

• saulecabrera: winch

To subscribe or unsubscribe from this label, edit the .github/subscribe-to-label.json configuration file.

Learn more.

[github-actions]

Label Messager: wasmtime:config

It looks like you are changing Wasmtime's configuration options. Make sure to
complete this check list:

• If you added a new Config method, you wrote extensive documentation for
  it.

  Our documentation should be of the following form:

  Short, simple summary sentence.
  
  More details. These details can be multiple paragraphs. There should be
  information about not just the method, but its parameters and results as
  well.
  
  Is this method fallible? If so, when can it return an error?
  
  Can this method panic? If so, when does it panic?
  
  # Example
  
  Optional example here.
  

• If you added a new Config method, or modified an existing one, you
  ensured that this configuration is exercised by the fuzz targets.

  For example, if you expose a new strategy for allocating the next instance
  slot inside the pooling allocator, you should ensure that at least one of our
  fuzz targets exercises that new strategy.

  Often, all that is required of you is to ensure that there is a knob for this
  configuration option in wasmtime_fuzzing::Config (or one
  of its nested structs).

  Rarely, this may require authoring a new fuzz target to specifically test this
  configuration. See our docs on fuzzing for more details.

• If you are enabling a configuration option by default, make sure that it
  has been fuzzed for at least two weeks before turning it on by default.

---

To modify this label's message, edit the .github/label-messager/wasmtime-config.md file.

To add new label messages or remove existing label messages, edit the
.github/label-messager.json configuration file.

Learn more.