Update reference types (#3084)

Align with the current state of the reference types proposal:
* Remove `nullref`
* Remove `externref` and `funcref` subtyping
* A `Literal` of a nullable reference type can now represent `null` (previously was type `nullref`)
* Update the tests and temporarily comment out those tests relying on subtyping

4 files changed, 16 insertions, 47 deletions

diff --git a/src/tools/execution-results.h b/src/tools/execution-results.h
index 38989aedf..c41b0c208 100644
--- a/src/tools/execution-results.h
+++ b/src/tools/execution-results.h
@@ -74,7 +74,7 @@ struct ExecutionResults {
           // while the function contents are still the same
           for (Literal& val : ret) {
             if (val.type == Type::funcref) {
-              val = Literal::makeFuncref(Name("funcref"));
+              val = Literal::makeFunc(Name("funcref"));
             }
           }
           results[exp->name] = ret;
diff --git a/src/tools/fuzzing.h b/src/tools/fuzzing.h
index b3c1212d4..ef7844c60 100644
--- a/src/tools/fuzzing.h
+++ b/src/tools/fuzzing.h
@@ -315,21 +315,7 @@ private:
     }
     SmallVector<Type, 2> options;
     options.push_back(type); // includes itself
-    TODO_SINGLE_COMPOUND(type);
-    switch (type.getBasic()) {
-      case Type::externref:
-        if (wasm.features.hasExceptionHandling()) {
-          options.push_back(Type::exnref);
-        }
-        options.push_back(Type::funcref);
-        // falls through
-      case Type::funcref:
-      case Type::exnref:
-        options.push_back(Type::nullref);
-        break;
-      default:
-        break;
-    }
+    // TODO (GC): subtyping
     return pick(options);
   }
 
@@ -1362,7 +1348,6 @@ private:
       }
       case Type::funcref:
       case Type::externref:
-      case Type::nullref:
       case Type::exnref:
       case Type::none:
       case Type::unreachable:
@@ -1466,7 +1451,6 @@ private:
       }
       case Type::funcref:
       case Type::externref:
-      case Type::nullref:
       case Type::exnref:
       case Type::none:
       case Type::unreachable:
@@ -1595,7 +1579,6 @@ private:
           case Type::v128:
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
           case Type::none:
           case Type::unreachable:
@@ -1640,7 +1623,6 @@ private:
           case Type::v128:
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
           case Type::none:
           case Type::unreachable:
@@ -1708,7 +1690,6 @@ private:
           case Type::v128:
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
           case Type::none:
           case Type::unreachable:
@@ -1735,7 +1716,6 @@ private:
           case Type::v128:
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
           case Type::none:
           case Type::unreachable:
@@ -1763,7 +1743,7 @@ private:
         }
         return builder.makeRefFunc(target->name);
       }
-      return builder.makeRefNull();
+      return builder.makeRefNull(type);
     }
     if (type.isTuple()) {
       std::vector<Expression*> operands;
@@ -1845,7 +1825,6 @@ private:
           }
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
             return makeTrivial(type);
           case Type::none:
@@ -1990,7 +1969,6 @@ private:
       }
       case Type::funcref:
       case Type::externref:
-      case Type::nullref:
       case Type::exnref:
       case Type::none:
       case Type::unreachable:
@@ -2227,7 +2205,6 @@ private:
       }
       case Type::funcref:
       case Type::externref:
-      case Type::nullref:
       case Type::exnref:
       case Type::none:
       case Type::unreachable:
@@ -2434,7 +2411,6 @@ private:
       case Type::v128:
       case Type::funcref:
       case Type::externref:
-      case Type::nullref:
       case Type::exnref:
       case Type::none:
       case Type::unreachable:
@@ -2610,14 +2586,13 @@ private:
   Expression* makeRefIsNull(Type type) {
     assert(type == Type::i32);
     assert(wasm.features.hasReferenceTypes());
-    Type refType;
+    SmallVector<Type, 2> options;
+    options.push_back(Type::externref);
+    options.push_back(Type::funcref);
     if (wasm.features.hasExceptionHandling()) {
-      refType =
-        pick(Type::funcref, Type::externref, Type::nullref, Type::exnref);
-    } else {
-      refType = pick(Type::funcref, Type::externref, Type::nullref);
+      options.push_back(Type::exnref);
     }
-    return builder.makeRefIsNull(make(refType));
+    return builder.makeRefIsNull(make(pick(options)));
   }
 
   Expression* makeMemoryInit() {
@@ -2680,10 +2655,7 @@ private:
       FeatureOptions<Type>()
         .add(FeatureSet::MVP, Type::i32, Type::i64, Type::f32, Type::f64)
         .add(FeatureSet::SIMD, Type::v128)
-        .add(FeatureSet::ReferenceTypes,
-             Type::funcref,
-             Type::externref,
-             Type::nullref)
+        .add(FeatureSet::ReferenceTypes, Type::funcref, Type::externref)
         .add(FeatureSet::ReferenceTypes | FeatureSet::ExceptionHandling,
              Type::exnref));
   }
@@ -2732,7 +2704,6 @@ private:
       FeatureOptions<Type>()
         .add(FeatureSet::MVP, Type::i32, Type::i64, Type::f32, Type::f64)
         .add(FeatureSet::SIMD, Type::v128)
-        .add(FeatureSet::ReferenceTypes, Type::nullref)
         .add(FeatureSet::ReferenceTypes | FeatureSet::ExceptionHandling,
              Type::exnref));
   }
diff --git a/src/tools/spec-wrapper.h b/src/tools/spec-wrapper.h
index 44f92b56d..c073a994c 100644
--- a/src/tools/spec-wrapper.h
+++ b/src/tools/spec-wrapper.h
@@ -50,10 +50,13 @@ static std::string generateSpecWrapper(Module& wasm) {
           ret += "(v128.const i32x4 0 0 0 0)";
           break;
         case Type::funcref:
+          ret += "(ref.null func)";
+          break;
         case Type::externref:
-        case Type::nullref:
+          ret += "(ref.null extern)";
+          break;
         case Type::exnref:
-          ret += "(ref.null)";
+          ret += "(ref.null exn)";
           break;
         case Type::none:
         case Type::unreachable:
diff --git a/src/tools/wasm-reduce.cpp b/src/tools/wasm-reduce.cpp
index 9c9978b63..1a7c3544d 100644
--- a/src/tools/wasm-reduce.cpp
+++ b/src/tools/wasm-reduce.cpp
@@ -597,7 +597,6 @@ struct Reducer
               case Type::v128:
               case Type::funcref:
               case Type::externref:
-              case Type::nullref:
               case Type::exnref:
                 continue; // not implemented yet
               case Type::none:
@@ -623,7 +622,6 @@ struct Reducer
               case Type::v128:
               case Type::funcref:
               case Type::externref:
-              case Type::nullref:
               case Type::exnref:
                 continue; // not implemented yet
               case Type::none:
@@ -649,7 +647,6 @@ struct Reducer
               case Type::v128:
               case Type::funcref:
               case Type::externref:
-              case Type::nullref:
               case Type::exnref:
                 continue; // not implemented yet
               case Type::none:
@@ -675,7 +672,6 @@ struct Reducer
               case Type::v128:
               case Type::funcref:
               case Type::externref:
-              case Type::nullref:
               case Type::exnref:
                 continue; // not implemented yet
               case Type::none:
@@ -687,7 +683,6 @@ struct Reducer
           case Type::v128:
           case Type::funcref:
           case Type::externref:
-          case Type::nullref:
           case Type::exnref:
             continue; // not implemented yet
           case Type::none:
@@ -1015,8 +1010,8 @@ struct Reducer
       return false;
     }
     // try to replace with a trivial value
-    if (curr->type.isRef()) {
-      RefNull* n = builder->makeRefNull();
+    if (curr->type.isNullable()) {
+      RefNull* n = builder->makeRefNull(curr->type);
       return tryToReplaceCurrent(n);
     }
     if (curr->type.isTuple()) {