Add initial support for anyref as an opaque type (#2294)

Another round of trying to push upstream things from my fork.

This PR only adds support for anyref itself as an opaque type. It does NOT implement the full [reference types proposal](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md)--so no table.get/set/grow/etc or ref.null, ref.func, etc.

Figured it was easier to review and merge as we go, especially if I did something fundamentally wrong.

***

I did put it under the `--enable-reference-types` flag as I imagine that even though this PR doesn't complete the full feature set, it probably is the right home. Lmk if not.

I'll also be adding a few github comments to places I want to point out/question.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 7047b674e..d75973ab0 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -681,6 +681,8 @@ void WasmBinaryWriter::writeFeaturesSection() {
         return BinaryConsts::UserSections::ExceptionHandlingFeature;
       case FeatureSet::TailCall:
         return BinaryConsts::UserSections::TailCallFeature;
+      case FeatureSet::ReferenceTypes:
+        return BinaryConsts::UserSections::ReferenceTypesFeature;
       default:
         WASM_UNREACHABLE();
     }
@@ -1085,6 +1087,8 @@ Type WasmBinaryBuilder::getType() {
       return f64;
     case BinaryConsts::EncodedType::v128:
       return v128;
+    case BinaryConsts::EncodedType::anyref:
+      return anyref;
     case BinaryConsts::EncodedType::exnref:
       return exnref;
     default: { throwError("invalid wasm type: " + std::to_string(type)); }
@@ -2167,6 +2171,8 @@ void WasmBinaryBuilder::readFeatures(size_t payloadLen) {
         wasm.features.setSIMD();
       } else if (name == BinaryConsts::UserSections::TailCallFeature) {
         wasm.features.setTailCall();
+      } else if (name == BinaryConsts::UserSections::ReferenceTypesFeature) {
+        wasm.features.setReferenceTypes();
       }
     }
   }