winch: Implement check_stack for aarch64

[graydon]

This is my first attempt at contributing to winch or cranelift at all -- wide open to any feedback/suggestions. I was just poking around looking for things I could do to help push winch over the finish line on aarch64. @saulecabrera suggested the missing check_stack implementation might be a welcome change.

(This is also my first time working with aarch64 instructions in any detail; hopefully I got the semantics not-too-wrong)

Before:

$ cargo run -- wast -Ccompiler=winch tests/spec_testsuite/call.wast
[...]
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.41s
     Running `target/debug/wasmtime wast -Ccompiler=winch tests/spec_testsuite/call.wast`
execution on async fiber has overflowed its stackzsh: abort      cargo run -- wast -Ccompiler=winch tests/spec_testsuite/call.wast

After:

$ cargo run -- wast -Ccompiler=winch tests/spec_testsuite/call.wast
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.41s
     Running `target/debug/wasmtime wast -Ccompiler=winch tests/spec_testsuite/call.wast`
Error: failed to run script file 'tests/spec_testsuite/call.wast'

Caused by:
    0: failed directive on tests/spec_testsuite/call.wast:285:1
    1: error while executing at wasm backtrace:
           0: <unknown>!<wasm function 17>
    2: wasm trap: call stack exhausted

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[alexcrichton]

(moving review over to @saulecabrera)

Looks like you found WASMTIME_TEST_BLESS=1 though which is indeed the recommend way to fix the original test failures 👍

[saulecabrera]

This is looking really good, thanks! I left a couple of comments inline, which I think is probably worth addressing.

In terms of tests, since our last discussion via Zulip, #10750 landed, which enables running some aarch64 tests in CI. It's probably a good idea to enable at least the call.wast tests here https://github.com/bytecodealliance/wasmtime/blob/main/crates/test-util/src/wast.rs#L422. Ideally, we should enable all of them, but it's possible that some of them will fail, due to some of the existing bugs that I'm currently in the process of fixing.

[graydon]

@saulecabrera thanks for the review! one thing worth pointing out is that this change doesn't include the bit about emitting unwind instructions that's in the x86_64 masm. I got the impression that's a larger project though (there doesn't seem to be any unwind support in the aarch64 backend at all right now -- is that something else that needs doing?)

[saulecabrera]

@graydon You're right that there is no unwind support right now, it's not expected to land that functionality as part of this PR. I think that once that (any passing) tests are updated here https://github.com/bytecodealliance/wasmtime/blob/main/crates/test-util/src/wast.rs#L422, we should be able to land this one.

[saulecabrera]

LGTM, thanks!