Several fixes for reference types (#1278)

- Allow `ref.func` for global initialization expressions
- Allow `nullref` as a full-fledged type, after
  WebAssembly/reference-types#66
- Enable reference types when exnref is used (The reference types
  proposal is a prerequisite of the EH proposal)

Author: aheejin

README.md

@@ -54,7 +54,7 @@ Wabt has been compiled to JavaScript via emscripten. Some of the functionality i
 | [multi-value][] | `--enable-multi-value` | ✓ | ✓ | ✓ | ✓ |
 | [tail-call][] | `--enable-tail-call` | ✓ | ✓ | ✓ | ✓ |
 | [bulk memory][] | `--enable-bulk-memory` | ✓ | ✓ | ✓ | ✓ |
-| [reference types][] | `--enable-reference-types` | ✓ | ✓ | ✓ | |
+| [reference types][] | `--enable-reference-types` | ✓ | ✓ | ✓ | ✓ |
 | [annotations][] | `--enable-annotations` | | ✓ | | |
 
 [exception handling]: https://github.com/WebAssembly/exception-handling

src/binary-reader-ir.cc

@@ -245,6 +245,7 @@ class BinaryReaderIR : public BinaryReaderNop {
   Result OnInitExprI32ConstExpr(Index index, uint32_t value) override;
   Result OnInitExprI64ConstExpr(Index index, uint64_t value) override;
   Result OnInitExprRefNull(Index index) override;
+  Result OnInitExprRefFunc(Index index, Index func_index) override;
 
  private:
   Location GetLocation() const;
@@ -1197,6 +1198,13 @@ Result BinaryReaderIR::OnInitExprRefNull(Index index) {
   return Result::Ok;
 }
 
+Result BinaryReaderIR::OnInitExprRefFunc(Index index, Index func_index) {
+  Location loc = GetLocation();
+  current_init_expr_->push_back(
+      MakeUnique<RefFuncExpr>(Var(func_index, loc), loc));
+  return Result::Ok;
+}
+
 Result BinaryReaderIR::OnLocalName(Index func_index,
                                    Index local_index,
                                    string_view name) {

src/binary-reader.cc

@@ -394,14 +394,14 @@ bool BinaryReader::IsConcreteType(Type type) {
     case Type::V128:
       return options_.features.simd_enabled();
 
-    case Type::Exnref:
-      return options_.features.exceptions_enabled();
-
+    case Type::Funcref:
     case Type::Anyref:
+    case Type::Nullref:
       return options_.features.reference_types_enabled();
 
-    case Type::Funcref:
-      return options_.features.reference_types_enabled();
+    case Type::Exnref:
+      return options_.features.reference_types_enabled() &&
+             options_.features.exceptions_enabled();
 
     default:
       return false;
@@ -525,9 +525,8 @@ Result BinaryReader::ReadInitExpr(Index index, bool require_i32) {
 
 Result BinaryReader::ReadTable(Type* out_elem_type, Limits* out_elem_limits) {
   CHECK_RESULT(ReadType(out_elem_type, "table elem type"));
-  ERROR_UNLESS(
-      *out_elem_type == Type::Funcref || *out_elem_type == Type::Anyref,
-      "table elem type must by funcref or anyref");
+  ERROR_UNLESS(IsRefType(*out_elem_type),
+               "table elem type must be a reference type");
 
   uint32_t flags;
   uint32_t initial;
@@ -2190,10 +2189,9 @@ Result BinaryReader::ReadElemSection(Offset section_size) {
     if (!legacy) {
       if (flags & SegUseElemExprs) {
         CHECK_RESULT(ReadType(&elem_type, "table elem type"));
-        ERROR_UNLESS(
-            elem_type == Type::Funcref || elem_type == Type::Anyref,
-            "segment elem expr type must be funcref or anyref (got %s)",
-            GetTypeName(elem_type));
+        ERROR_UNLESS(IsRefType(elem_type),
+                     "segment elem expr type must be a reference type (got %s)",
+                     GetTypeName(elem_type));
       } else {
         ExternalKind kind;
         CHECK_RESULT(ReadExternalKind(&kind, "export kind"));

src/common.h

@@ -214,12 +214,12 @@ enum class Type : int32_t {
   V128 = -0x05,     // 0x7b
   Funcref = -0x10,  // 0x70
   Anyref = -0x11,   // 0x6f
+  Nullref = -0x12,  // 0x6e
   Exnref = -0x18,   // 0x68
   Func = -0x20,     // 0x60
   Void = -0x40,     // 0x40
   ___ = Void,       // Convenient for the opcode table in opcode.h
   Any = 0,          // Not actually specified, but useful for type-checking
-  Nullref = 1,      // Not actually specified, but used in testing and type-checking
   Hostref = 2,      // Not actually specified, but used in testing and type-checking
   I8 = 3,           // Not actually specified, but used internally with load/store
   I8U = 4,          // Not actually specified, but used internally with load/store
@@ -383,7 +383,7 @@ static WABT_INLINE const char* GetSymbolTypeName(SymbolType type) {
 
 static WABT_INLINE bool IsRefType(Type t) {
   return t == Type::Anyref || t == Type::Funcref || t == Type::Nullref ||
-         t == Type::Hostref;
+         t == Type::Exnref || t == Type::Hostref;
 }
 
 static WABT_INLINE bool IsNullableRefType(Type t) {
@@ -444,6 +444,7 @@ static WABT_INLINE TypeVector GetInlineTypeVector(Type type) {
     case Type::V128:
     case Type::Funcref:
     case Type::Anyref:
+    case Type::Nullref:
     case Type::Exnref:
       return TypeVector(&type, &type + 1);
 

src/decompiler-ls.h

@@ -36,10 +36,11 @@ inline const char *GetDecompTypeName(Type t) {
     case Type::F32: return "float";
     case Type::F64: return "double";
     case Type::V128: return "simd";
-    case Type::Anyref: return "anyref";
     case Type::Func: return "func";
     case Type::Funcref: return "funcref";
-    case Type::Exnref: return "exceptionref";
+    case Type::Anyref: return "anyref";
+    case Type::Nullref: return "nullref";
+    case Type::Exnref: return "exnref";
     case Type::Void: return "void";
     default: return "ILLEGAL";
   }

src/lexer-keywords.txt

@@ -442,6 +442,7 @@ memory, TokenType::Memory
 module, TokenType::Module
 mut, TokenType::Mut
 nop, TokenType::Nop, Opcode::Nop
+nullref, Type::Nullref
 offset, TokenType::Offset
 param, TokenType::Param
 quote, TokenType::Quote