[wasm][jiterp] RelaxedSimd jiterpreter intrinsics

[lewing]

This is just a first step to allow the Jiterpreter to use the potentially faster relaxed_swizzle in the case where we know the swizzle indices are valid and can detect at runtime the opcode is supported. There is follow-up work planned to use the relaxed_swizzle in more cases, but this is a good first step to get the infrastructure in place

[kg]

Lgtm

[Copilot]

Pull Request Overview

This PR introduces support for relaxed_simd intrinsics in the Jiterpreter to enable potentially faster SIMD swizzle operations. The changes add new fields to helper types, update the import of relaxedSimd from the wasm‐feature‐detect package, and use the new relaxed swizzle opcode in the trace generator when the feature is available.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/mono/browser/runtime/types/internal.ts	Added relaxedSimd and featureWasmRelaxedSimd to helper types
src/mono/browser/runtime/loader/globals.ts	Updated the import to include relaxedSimd from wasm-feature-detect
src/mono/browser/runtime/jiterpreter-trace-generator.ts	Conditionally emits i8x16_relaxed_swizzle if feature is enabled

Comments suppressed due to low confidence (1)

src/mono/browser/runtime/loader/globals.ts:7

• [nitpick] Please verify that the version of the wasm-feature-detect package being used supports the relaxedSimd API to prevent potential runtime issues.

import { exceptions, simd, relaxedSimd } from "wasm-feature-detect";

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