Bug 251133 – [Wasm-GC] Fix null checks for struct operations

• Component: WebAssembly
• Status: RESOLVED FIXED

[Asumu Takikawa]

There's a bug in the implementation of Wasm GC struct instructions such as `struct.get` and `struct.set`, in that they don't correctly implement null ref checks.

Here's an example test case (can run in the JSTests/wasm/gc test directory):

```
import * as assert from "../assert.js";
import { compile, instantiate } from "./wast-wrapper.js";

let m = instantiate(`
  (module
    (type (struct (field i32)))
    (func (export "f") (result i32)
      (struct.get 0 0 (ref.null 0)))
  )
`);

m.exports.f();
```

This currently crashes, instead of raising a trap exception as needed.

[Asumu Takikawa]

Pull request: https://github.com/WebKit/WebKit/pull/9091

[EWS]

Committed 259449@main (a5a87681d68f): <https://commits.webkit.org/259449@main>

Reviewed commits have been landed. Closing PR #9091 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/104707623>