Add except_ref type (#2081)

This adds except_ref type, which is a part of the exception handling
proposal.

24 files changed, 121 insertions, 7 deletions

diff --git a/src/asmjs/asm_v_wasm.cpp b/src/asmjs/asm_v_wasm.cpp
index bbc7dabd9..aa247153d 100644
--- a/src/asmjs/asm_v_wasm.cpp
+++ b/src/asmjs/asm_v_wasm.cpp
@@ -53,6 +53,8 @@ AsmType wasmToAsmType(Type type) {
       return ASM_INT64;
     case v128:
       assert(false && "v128 not implemented yet");
+    case except_ref:
+      assert(false && "except_ref is not in asm2wasm");
     case none:
       return ASM_NONE;
     case unreachable:
@@ -73,6 +75,8 @@ char getSig(Type type) {
       return 'd';
     case v128:
       return 'V';
+    case except_ref:
+      return 'e';
     case none:
       return 'v';
     case unreachable:
@@ -111,6 +115,8 @@ Type sigToType(char sig) {
       return f64;
     case 'V':
       return v128;
+    case 'e':
+      return except_ref;
     case 'v':
       return none;
     default:
diff --git a/src/binaryen-c.cpp b/src/binaryen-c.cpp
index b3b52bfcf..ffd24d48e 100644
--- a/src/binaryen-c.cpp
+++ b/src/binaryen-c.cpp
@@ -66,6 +66,8 @@ BinaryenLiteral toBinaryenLiteral(Literal x) {
       memcpy(&ret.v128, x.getv128Ptr(), 16);
       break;
     }
+
+    case Type::except_ref: // there's no except_ref literals
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -85,6 +87,7 @@ Literal fromBinaryenLiteral(BinaryenLiteral x) {
       return Literal(x.i64).castToF64();
     case Type::v128:
       return Literal(x.v128);
+    case Type::except_ref: // there's no except_ref literals
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -203,6 +206,7 @@ void printArg(std::ostream& setup, std::ostream& out, BinaryenLiteral arg) {
       out << "BinaryenLiteralVec128(" << array << ")";
       break;
     }
+    case Type::except_ref: // there's no except_ref literals
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -257,6 +261,7 @@ BinaryenType BinaryenTypeInt64(void) { return i64; }
 BinaryenType BinaryenTypeFloat32(void) { return f32; }
 BinaryenType BinaryenTypeFloat64(void) { return f64; }
 BinaryenType BinaryenTypeVec128(void) { return v128; }
+BinaryenType BinaryenTypeExceptRef(void) { return except_ref; }
 BinaryenType BinaryenTypeUnreachable(void) { return unreachable; }
 BinaryenType BinaryenTypeAuto(void) { return uint32_t(-1); }
 
diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index 9a57cac79..62ffa4348 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -74,6 +74,7 @@ BinaryenType BinaryenTypeInt64(void);
 BinaryenType BinaryenTypeFloat32(void);
 BinaryenType BinaryenTypeFloat64(void);
 BinaryenType BinaryenTypeVec128(void);
+BinaryenType BinaryenTypeExceptRef(void);
 BinaryenType BinaryenTypeUnreachable(void);
 // Not a real type. Used as the last parameter to BinaryenBlock to let
 // the API figure out the type instead of providing one.
diff --git a/src/ir/abstract.h b/src/ir/abstract.h
index 33c276409..2cc016f97 100644
--- a/src/ir/abstract.h
+++ b/src/ir/abstract.h
@@ -81,6 +81,7 @@ inline UnaryOp getUnary(Type type, Op op) {
       assert(false && "v128 not implemented yet");
       WASM_UNREACHABLE();
     }
+    case except_ref: // there's no unary instructions for except_ref
     case none:
     case unreachable: {
       return InvalidUnary;
@@ -211,6 +212,7 @@ inline BinaryOp getBinary(Type type, Op op) {
       assert(false && "v128 not implemented yet");
       WASM_UNREACHABLE();
     }
+    case except_ref: // there's no binary instructions for except_ref
     case none:
     case unreachable: {
       return InvalidBinary;
diff --git a/src/js/binaryen.js-post.js b/src/js/binaryen.js-post.js
index b9f6b426c..52f4743bb 100644
--- a/src/js/binaryen.js-post.js
+++ b/src/js/binaryen.js-post.js
@@ -37,6 +37,7 @@ Module['i64'] = Module['_BinaryenTypeInt64']();
 Module['f32'] = Module['_BinaryenTypeFloat32']();
 Module['f64'] = Module['_BinaryenTypeFloat64']();
 Module['v128'] = Module['_BinaryenTypeVec128']();
+Module['except_ref'] = Module['_BinaryenTypeExceptRef']();
 Module['unreachable'] = Module['_BinaryenTypeUnreachable']();
 Module['auto'] = /* deprecated */ Module['undefined'] = Module['_BinaryenTypeAuto']();
 
diff --git a/src/literal.h b/src/literal.h
index 9ffa79032..b5ffc491b 100644
--- a/src/literal.h
+++ b/src/literal.h
@@ -80,6 +80,7 @@ public:
                                                Literal(int32_t(0)),
                                                Literal(int32_t(0)),
                                                Literal(int32_t(0))}});
+      case Type::except_ref: // there's no except_ref literals
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -429,6 +430,7 @@ template<> struct less<wasm::Literal> {
         return a.reinterpreti64() < b.reinterpreti64();
       case wasm::Type::v128:
         return memcmp(a.getv128Ptr(), b.getv128Ptr(), 16) < 0;
+      case wasm::Type::except_ref: // except_ref is an opaque value
       case wasm::Type::none:
       case wasm::Type::unreachable:
         return false;
diff --git a/src/parsing.h b/src/parsing.h
index 9b2cb490b..22eb663a1 100644
--- a/src/parsing.h
+++ b/src/parsing.h
@@ -263,6 +263,7 @@ parseConst(cashew::IString s, Type type, MixedArena& allocator) {
       break;
     }
     case v128:
+    case except_ref: // there's no except_ref.const
       WASM_UNREACHABLE();
     case none:
     case unreachable: {
diff --git a/src/passes/ConstHoisting.cpp b/src/passes/ConstHoisting.cpp
index 749a3361f..37799e8b8 100644
--- a/src/passes/ConstHoisting.cpp
+++ b/src/passes/ConstHoisting.cpp
@@ -95,6 +95,10 @@ private:
         // v128 not implemented yet
         return false;
       }
+      case except_ref: {
+        // except_ref cannot have literals
+        return false;
+      }
       case none:
       case unreachable: {
         WASM_UNREACHABLE();
diff --git a/src/passes/FuncCastEmulation.cpp b/src/passes/FuncCastEmulation.cpp
index 904b8a202..ce5332a49 100644
--- a/src/passes/FuncCastEmulation.cpp
+++ b/src/passes/FuncCastEmulation.cpp
@@ -66,6 +66,10 @@ static Expression* toABI(Expression* value, Module* module) {
       assert(false && "v128 not implemented yet");
       WASM_UNREACHABLE();
     }
+    case except_ref: {
+      assert(false && "except_ref cannot be converted to i64");
+      WASM_UNREACHABLE();
+    }
     case none: {
       // the value is none, but we need a value here
       value = builder.makeSequence(value, LiteralUtils::makeZero(i64, *module));
@@ -104,6 +108,10 @@ static Expression* fromABI(Expression* value, Type type, Module* module) {
       assert(false && "v128 not implemented yet");
       WASM_UNREACHABLE();
     }
+    case except_ref: {
+      assert(false && "except_ref cannot be converted from i64");
+      WASM_UNREACHABLE();
+    }
     case none: {
       value = builder.makeDrop(value);
     }
diff --git a/src/passes/InstrumentLocals.cpp b/src/passes/InstrumentLocals.cpp
index 3845b0fee..45d4d484b 100644
--- a/src/passes/InstrumentLocals.cpp
+++ b/src/passes/InstrumentLocals.cpp
@@ -81,6 +81,8 @@ struct InstrumentLocals : public WalkerPass<PostWalker<InstrumentLocals>> {
         break;
       case v128:
         assert(false && "v128 not implemented yet");
+      case except_ref:
+        assert(false && "not implemented yet");
       case none:
         WASM_UNREACHABLE();
       case unreachable:
@@ -111,6 +113,8 @@ struct InstrumentLocals : public WalkerPass<PostWalker<InstrumentLocals>> {
         break;
       case v128:
         assert(false && "v128 not implemented yet");
+      case except_ref:
+        assert(false && "except_ref not implemented yet");
       case unreachable:
         return; // nothing to do here
       case none:
diff --git a/src/shell-interface.h b/src/shell-interface.h
index c07203a92..dc455ee81 100644
--- a/src/shell-interface.h
+++ b/src/shell-interface.h
@@ -114,6 +114,8 @@ struct ShellExternalInterface : ModuleInstance::ExternalInterface {
             break;
           case v128:
             assert(false && "v128 not implemented yet");
+          case except_ref:
+            assert(false && "except_ref not implemented yet");
           case none:
           case unreachable:
             WASM_UNREACHABLE();
diff --git a/src/tools/fuzzing.h b/src/tools/fuzzing.h
index 16b04fe02..b9a9fe4ff 100644
--- a/src/tools/fuzzing.h
+++ b/src/tools/fuzzing.h
@@ -25,6 +25,9 @@ high chance for set at start of loop
     high chance of a tee in that case => loop var
 */
 
+// TODO Complete except_ref type support. Its support is partialy implemented
+// and the type is currently not generated in fuzzed programs yet.
+
 #include "ir/memory-utils.h"
 #include <ir/find_all.h>
 #include <ir/literal-utils.h>
@@ -815,6 +818,7 @@ private:
       case f32:
       case f64:
       case v128:
+      case except_ref:
         ret = _makeConcrete(type);
         break;
       case none:
@@ -1326,6 +1330,7 @@ private:
         return builder.makeLoad(
           16, false, offset, pick(1, 2, 4, 8, 16), ptr, type);
       }
+      case except_ref: // except_ref cannot be loaded from memory
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -1334,7 +1339,8 @@ private:
   }
 
   Expression* makeLoad(Type type) {
-    if (!allowMemory) {
+    // except_ref type cannot be stored in memory
+    if (!allowMemory || type == except_ref) {
       return makeTrivial(type);
     }
     auto* ret = makeNonAtomicLoad(type);
@@ -1425,6 +1431,7 @@ private:
         return builder.makeStore(
           16, offset, pick(1, 2, 4, 8, 16), ptr, value, type);
       }
+      case except_ref: // except_ref cannot be stored in memory
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -1433,7 +1440,8 @@ private:
   }
 
   Expression* makeStore(Type type) {
-    if (!allowMemory) {
+    // except_ref type cannot be stored in memory
+    if (!allowMemory || type == except_ref) {
       return makeTrivial(type);
     }
     auto* ret = makeNonAtomicStore(type);
@@ -1518,6 +1526,7 @@ private:
           case f64:
             return Literal(getDouble());
           case v128:
+          case except_ref: // except_ref cannot have literals
           case none:
           case unreachable:
             WASM_UNREACHABLE();
@@ -1559,6 +1568,7 @@ private:
           case f64:
             return Literal(double(small));
           case v128:
+          case except_ref: // except_ref cannot have literals
           case none:
           case unreachable:
             WASM_UNREACHABLE();
@@ -1623,6 +1633,7 @@ private:
                                          std::numeric_limits<uint64_t>::max()));
             break;
           case v128:
+          case except_ref: // except_ref cannot have literals
           case none:
           case unreachable:
             WASM_UNREACHABLE();
@@ -1653,6 +1664,7 @@ private:
             value = Literal(double(int64_t(1) << upTo(64)));
             break;
           case v128:
+          case except_ref: // except_ref cannot have literals
           case none:
           case unreachable:
             WASM_UNREACHABLE();
@@ -1676,6 +1688,12 @@ private:
   }
 
   Expression* makeConst(Type type) {
+    if (type == except_ref) {
+      // There's no except_ref.const.
+      // TODO We should return a nullref once we implement instructions for
+      // reference types proposal.
+      assert(false && "except_ref const is not implemented yet");
+    }
     auto* ret = wasm.allocator.alloc<Const>();
     ret->value = makeLiteral(type);
     ret->type = type;
@@ -1694,6 +1712,11 @@ private:
       // give up
       return makeTrivial(type);
     }
+    // There's no binary ops for except_ref
+    if (type == except_ref) {
+      makeTrivial(type);
+    }
+
     switch (type) {
       case i32: {
         switch (getConcreteType()) {
@@ -1739,6 +1762,7 @@ private:
                                     AllTrueVecI64x2),
                                make(v128)});
           }
+          case except_ref: // there's no unary ops for except_ref
           case none:
           case unreachable:
             WASM_UNREACHABLE();
@@ -1869,6 +1893,7 @@ private:
         }
         WASM_UNREACHABLE();
       }
+      case except_ref: // there's no unary ops for except_ref
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -1889,6 +1914,11 @@ private:
       // give up
       return makeTrivial(type);
     }
+    // There's no binary ops for except_ref
+    if (type == except_ref) {
+      makeTrivial(type);
+    }
+
     switch (type) {
       case i32: {
         switch (upTo(4)) {
@@ -2076,6 +2106,7 @@ private:
                             make(v128),
                             make(v128)});
       }
+      case except_ref: // there's no binary ops for except_ref
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -2269,6 +2300,7 @@ private:
         op = ExtractLaneVecF64x2;
         break;
       case v128:
+      case except_ref:
       case none:
       case unreachable:
         WASM_UNREACHABLE();
diff --git a/src/tools/spec-wrapper.h b/src/tools/spec-wrapper.h
index d481f0fa8..bb928b50d 100644
--- a/src/tools/spec-wrapper.h
+++ b/src/tools/spec-wrapper.h
@@ -48,6 +48,7 @@ static std::string generateSpecWrapper(Module& wasm) {
         case v128:
           ret += "(v128.const i32x4 0 0 0 0)";
           break;
+        case except_ref: // there's no except_ref.const
         case none:
         case unreachable:
           WASM_UNREACHABLE();
diff --git a/src/tools/wasm-reduce.cpp b/src/tools/wasm-reduce.cpp
index 54a915ec0..cea415a47 100644
--- a/src/tools/wasm-reduce.cpp
+++ b/src/tools/wasm-reduce.cpp
@@ -592,7 +592,8 @@ struct Reducer
                 fixed = builder->makeUnary(TruncSFloat64ToInt32, child);
                 break;
               case v128:
-                continue; // v128 not implemented yet
+              case except_ref:
+                continue; // not implemented yet
               case none:
               case unreachable:
                 WASM_UNREACHABLE();
@@ -613,7 +614,8 @@ struct Reducer
                 fixed = builder->makeUnary(TruncSFloat64ToInt64, child);
                 break;
               case v128:
-                continue; // v128 not implemented yet
+              case except_ref:
+                continue; // not implemented yet
               case none:
               case unreachable:
                 WASM_UNREACHABLE();
@@ -634,7 +636,8 @@ struct Reducer
                 fixed = builder->makeUnary(DemoteFloat64, child);
                 break;
               case v128:
-                continue; // v128 not implemented yet
+              case except_ref:
+                continue; // not implemented yet
               case none:
               case unreachable:
                 WASM_UNREACHABLE();
@@ -655,7 +658,8 @@ struct Reducer
               case f64:
                 WASM_UNREACHABLE();
               case v128:
-                continue; // v128 not implemented yet
+              case except_ref:
+                continue; // not implemented yet
               case none:
               case unreachable:
                 WASM_UNREACHABLE();
@@ -663,7 +667,8 @@ struct Reducer
             break;
           }
           case v128:
-            continue; // v128 not implemented yet
+          case except_ref:
+            continue; // not implemented yet
           case none:
           case unreachable:
             WASM_UNREACHABLE();
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 9937bb897..b4adcdcb4 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -379,6 +379,8 @@ enum EncodedType {
   v128 = -0x5, // 0x7b
   // elem_type
   AnyFunc = -0x10, // 0x70
+  // reference type
+  except_ref = -0x18, // 0x68
   // func_type form
   Func = -0x20, // 0x60
   // block_type
@@ -885,6 +887,9 @@ inline S32LEB binaryType(Type type) {
     case v128:
       ret = BinaryConsts::EncodedType::v128;
       break;
+    case except_ref:
+      ret = BinaryConsts::EncodedType::except_ref;
+      break;
     case unreachable:
       WASM_UNREACHABLE();
   }
diff --git a/src/wasm-builder.h b/src/wasm-builder.h
index 9024ea6b1..505074fd9 100644
--- a/src/wasm-builder.h
+++ b/src/wasm-builder.h
@@ -659,6 +659,9 @@ public:
         value = Literal(bytes.data());
         break;
       }
+      case except_ref:
+        // TODO Implement and return nullref
+        assert(false && "except_ref not implemented yet");
       case none:
         return ExpressionManipulator::nop(curr);
       case unreachable:
diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 02e065c5f..1de216800 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -1124,6 +1124,7 @@ public:
           return Literal(load64u(addr)).castToF64();
         case v128:
           return Literal(load128(addr).data());
+        case except_ref: // except_ref cannot be loaded from memory
         case none:
         case unreachable:
           WASM_UNREACHABLE();
@@ -1177,6 +1178,7 @@ public:
         case v128:
           store128(addr, value.getv128());
           break;
+        case except_ref: // except_ref cannot be stored in memory
         case none:
         case unreachable:
           WASM_UNREACHABLE();
diff --git a/src/wasm-stack.h b/src/wasm-stack.h
index 0355f60ee..8b02574eb 100644
--- a/src/wasm-stack.h
+++ b/src/wasm-stack.h
@@ -754,6 +754,7 @@ void StackWriter<Mode, Parent>::visitLoad(Load* curr) {
         // the pointer is unreachable, so we are never reached; just don't emit
         // a load
         return;
+      case except_ref: // except_ref cannot be loaded from memory
       case none:
         WASM_UNREACHABLE();
     }
@@ -863,6 +864,7 @@ void StackWriter<Mode, Parent>::visitStore(Store* curr) {
         o << int8_t(BinaryConsts::SIMDPrefix)
           << U32LEB(BinaryConsts::V128Store);
         break;
+      case except_ref: // except_ref cannot be stored in memory
       case none:
       case unreachable:
         WASM_UNREACHABLE();
@@ -1329,6 +1331,7 @@ void StackWriter<Mode, Parent>::visitConst(Const* curr) {
       }
       break;
     }
+    case except_ref: // there's no except_ref.const
     case none:
     case unreachable:
       WASM_UNREACHABLE();
diff --git a/src/wasm-type.h b/src/wasm-type.h
index fcaea04ec..6c8ea82a6 100644
--- a/src/wasm-type.h
+++ b/src/wasm-type.h
@@ -28,6 +28,7 @@ enum Type {
   f32,
   f64,
   v128,
+  except_ref,
   // none means no type, e.g. a block can have no return type. but unreachable
   // is different, as it can be "ignored" when doing type checking across
   // branches
@@ -43,6 +44,7 @@ bool isConcreteType(Type type);
 bool isFloatType(Type type);
 bool isIntegerType(Type type);
 bool isVectorType(Type type);
+bool isReferenceType(Type type);
 
 } // namespace wasm
 
diff --git a/src/wasm/literal.cpp b/src/wasm/literal.cpp
index 3d7303e23..48b58c3ca 100644
--- a/src/wasm/literal.cpp
+++ b/src/wasm/literal.cpp
@@ -137,6 +137,7 @@ void Literal::getBits(uint8_t (&buf)[16]) const {
     case Type::v128:
       memcpy(buf, &v128, sizeof(v128));
       break;
+    case Type::except_ref: // except_ref type is opaque
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -271,6 +272,7 @@ std::ostream& operator<<(std::ostream& o, Literal literal) {
       o << "i32x4 ";
       literal.printVec128(o, literal.getv128());
       break;
+    case Type::except_ref: // except_ref type is opaque
     case Type::unreachable:
       WASM_UNREACHABLE();
   }
@@ -473,6 +475,7 @@ Literal Literal::eqz() const {
     case Type::f64:
       return eq(Literal(double(0)));
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -491,6 +494,7 @@ Literal Literal::neg() const {
     case Type::f64:
       return Literal(int64_t(i64 ^ 0x8000000000000000ULL)).castToF64();
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -509,6 +513,7 @@ Literal Literal::abs() const {
     case Type::f64:
       return Literal(int64_t(i64 & 0x7fffffffffffffffULL)).castToF64();
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -610,6 +615,7 @@ Literal Literal::add(const Literal& other) const {
     case Type::f64:
       return Literal(getf64() + other.getf64());
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -628,6 +634,7 @@ Literal Literal::sub(const Literal& other) const {
     case Type::f64:
       return Literal(getf64() - other.getf64());
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -717,6 +724,7 @@ Literal Literal::mul(const Literal& other) const {
     case Type::f64:
       return Literal(getf64() * other.getf64());
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -934,6 +942,7 @@ Literal Literal::eq(const Literal& other) const {
     case Type::f64:
       return Literal(getf64() == other.getf64());
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -952,6 +961,7 @@ Literal Literal::ne(const Literal& other) const {
     case Type::f64:
       return Literal(getf64() != other.getf64());
     case Type::v128:
+    case Type::except_ref:
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index a29665a15..484bfb49c 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -1056,6 +1056,8 @@ Type WasmBinaryBuilder::getType() {
       return f64;
     case BinaryConsts::EncodedType::v128:
       return v128;
+    case BinaryConsts::EncodedType::except_ref:
+      return except_ref;
     default: { throwError("invalid wasm type: " + std::to_string(type)); }
   }
   WASM_UNREACHABLE();
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index a869aa08a..4eaf54eff 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -790,6 +790,9 @@ Type SExpressionWasmBuilder::stringToType(const char* str,
       return v128;
     }
   }
+  if (strncmp(str, "except_ref", 10) == 0 && (prefix || str[10] == 0)) {
+    return except_ref;
+  }
   if (allowError) {
     return none;
   }
diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index 449dff4db..091d851f6 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -36,6 +36,8 @@ const char* printType(Type type) {
       return "f64";
     case Type::v128:
       return "v128";
+    case Type::except_ref:
+      return "except_ref";
     case Type::unreachable:
       return "unreachable";
   }
@@ -54,6 +56,7 @@ unsigned getTypeSize(Type type) {
       return 8;
     case Type::v128:
       return 16;
+    case Type::except_ref: // except_ref type is opaque
     case Type::none:
     case Type::unreachable:
       WASM_UNREACHABLE();
@@ -110,4 +113,9 @@ bool isFloatType(Type type) {
 
 bool isVectorType(Type type) { return type == v128; }
 
+bool isReferenceType(Type type) {
+  // TODO Add other reference types later
+  return type == except_ref;
+}
+
 } // namespace wasm
diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index b84105c8d..7467f1f15 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -1053,6 +1053,7 @@ void FunctionValidator::validateMemBytes(uint8_t bytes,
       shouldBeEqual(
         bytes, uint8_t(16), curr, "expected v128 operation to touch 16 bytes");
       break;
+    case except_ref: // except_ref cannot be stored in memory
     case none:
       WASM_UNREACHABLE();
     case unreachable:
@@ -1616,6 +1617,7 @@ void FunctionValidator::validateAlignment(
     case v128:
     case unreachable:
       break;
+    case except_ref: // except_ref cannot be stored in memory
     case none:
       WASM_UNREACHABLE();
   }