[wasm] EquivalentTypes() should be symmetric

Fixed: v8:12935
Change-Id: Ib4dfdc276e6a9f465666b068bdbe31776429f359
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3687699
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80941}

src/wasm/wasm-subtyping.cc

@@ -248,7 +248,7 @@ V8_NOINLINE bool EquivalentTypes(ValueType type1, ValueType type2,
                                  const WasmModule* module1,
                                  const WasmModule* module2) {
   if (type1 == type2 && module1 == module2) return true;
-  if (!type1.has_index()) return type1 == type2;
+  if (!type1.has_index() || !type2.has_index()) return type1 == type2;
   if (type1.kind() != type2.kind()) return false;
 
   DCHECK(type1.has_index() && type2.has_index() &&

test/unittests/wasm/subtyping-unittest.cc

@@ -216,6 +216,17 @@ TEST_F(WasmSubtypingTest, Subtyping) {
       SUBTYPE(ref_type, kWasmAnyRef);
       // Only anyref is a subtype of anyref.
       SUBTYPE_IFF(kWasmAnyRef, ref_type, ref_type == kWasmAnyRef);
+
+      // Make sure symmetric relations are symmetric.
+      for (ValueType ref_type2 : ref_types) {
+        if (ref_type == ref_type2) {
+          EXPECT_TRUE(EquivalentTypes(ref_type, ref_type2, module, module1));
+          EXPECT_TRUE(EquivalentTypes(ref_type2, ref_type, module1, module));
+        } else {
+          EXPECT_FALSE(EquivalentTypes(ref_type, ref_type2, module, module1));
+          EXPECT_FALSE(EquivalentTypes(ref_type2, ref_type, module1, module));
+        }
+      }
     }
 
     // The rest of ref. types are unrelated.