[wasm][exnref] Reject non-nullable exnref in JS import/export

R=jkummerow@chromium.org

Change-Id: I0ba2deb1a9671d87e76fea7bfe76df9eee56442a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5920338
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#96489}

Author: thibaudmichaud

src/wasm/wasm-opcodes.cc

@@ -33,12 +33,13 @@ bool IsJSCompatibleSignature(const FunctionSig* sig) {
     // Rtts are internal-only. They should never be part of a signature.
     DCHECK(!type.is_rtt());
     if (type == kWasmS128) return false;
-    if (type == kWasmExnRef) return false;
     if (type.is_object_reference()) {
       switch (type.heap_representation_non_shared()) {
         case HeapType::kStringViewWtf8:
         case HeapType::kStringViewWtf16:
         case HeapType::kStringViewIter:
+        case HeapType::kExn:
+        case HeapType::kNoExn:
           return false;
         default:
           break;

test/mjsunit/wasm/exnref.js

@@ -653,3 +653,21 @@ d8.file.execute("test/mjsunit/wasm/exceptions-utils.js");
 
   assertTraps(kTrapRethrowNull, () => instance.exports.throw_noexn());
 })();
+
+(function TestJSNonNullableExnRef() {
+  print(arguments.callee.name);
+  let builder = new WasmModuleBuilder();
+  let import_sig = makeSig([], [wasmRefType(kWasmExnRef)]);
+  let imported = builder.addImport('m', 'i', import_sig);
+  builder.addFunction("call_import", kSig_v_v)
+      .addBody([
+          kExprCallFunction, imported,
+          kExprDrop,
+      ]).exportFunc();
+  let export_sig = makeSig([wasmRefType(kWasmExnRef)], []);
+  builder.addFunction("export", export_sig)
+      .addBody([]).exportFunc();
+  let instance = builder.instantiate({m: {i: () => {}}});
+  assertThrows(instance.exports.call_import);
+  assertThrows(instance.exports.export);
+})();