Don't Use WasmGC Instructions Just Yet (#990)

At some point we had to switch away from `wasm-opt` automatically
detecting the WebAssembly features, because they deprecated and turned
that into a no-op. Since then we specified that it should just use all
the features. This used to work all the time, but with the introduction
of reference types it now started optimizing some of those instructions
into instructions that are only available with the `WasmGC` proposal.
This slipped through because Chrome and Firefox already support `WasmGC`
but Safari does not... yet, because they also will start to support it
very soon. In the meantime and also to ensure `wasm-opt` isn't ever
going to sneak in any unwanted features, we now explicitly specify all
the features that we want to use.

.github/workflows/ci.yml

@@ -179,7 +179,19 @@ jobs:
         shell: bash
         run: |
           WASM_FILE=$(ls ${{ matrix.dist_path }}/*.wasm)
-          wasm-opt --all-features -O4 "$WASM_FILE" -o "$WASM_FILE"
+          wasm-opt \
+            --enable-bulk-memory \
+            --enable-mutable-globals \
+            --enable-nontrapping-float-to-int \
+            --enable-sign-ext \
+            --enable-simd \
+            --enable-extended-const \
+            --enable-multivalue \
+            --enable-reference-types \
+            --strip-dwarf \
+            --strip-producers \
+            --strip-target-features \
+            -O4 "$WASM_FILE" -o "$WASM_FILE"
 
       - name: Build (Tauri)
         if: matrix.platform == 'tauri'

buildCore.js

@@ -4,8 +4,9 @@ import fs from "fs";
 let toolchain = "";
 let profile = "debug";
 let cargoFlags = "";
+// Keep .github/workflows/ci.yml in sync with these flags, so wasm-opt works.
 let rustFlags =
-    "-C target-feature=+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext,+simd128,+extended-const,+multivalue";
+    "-C target-feature=+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext,+simd128,+extended-const,+multivalue,+reference-types";
 let wasmBindgenFlags = "--encode-into always --target web --reference-types";
 let target = "wasm32-unknown-unknown";
 let targetFolder = target;

wasm32-multivalue.json

@@ -10,7 +10,6 @@
     "exe-suffix": ".wasm",
     "generate-arange-section": false,
     "has-thread-local": true,
-    "is-builtin": false,
     "is-like-wasm": true,
     "limit-rdylib-exports": false,
     "linker": "rust-lld",