Add support for reference types proposal (#2451)

This adds support for the reference type proposal. This includes support
for all reference types (`anyref`, `funcref`(=`anyfunc`), and `nullref`)
and four new instructions: `ref.null`, `ref.is_null`, `ref.func`, and
new typed `select`. This also adds subtype relationship support between
reference types.

This does not include table instructions yet. This also does not include
wasm2js support.

Fixes #2444 and fixes #2447.

1 files changed, 32 insertions, 0 deletions

diff --git a/src/wasm.h b/src/wasm.h
index 48adf103b..c4dbd2f3f 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -531,6 +531,9 @@ public:
     MemoryFillId,
     PushId,
     PopId,
+    RefNullId,
+    RefIsNullId,
+    RefFuncId,
     TryId,
     ThrowId,
     RethrowId,
@@ -569,6 +572,8 @@ public:
 
 const char* getExpressionName(Expression* curr);
 
+Literal getLiteralFromConstExpression(Expression* curr);
+
 typedef ArenaVector<Expression*> ExpressionList;
 
 template<Expression::Id SID> class SpecificExpression : public Expression {
@@ -1008,6 +1013,7 @@ public:
   Expression* condition;
 
   void finalize();
+  void finalize(Type type_);
 };
 
 class Drop : public SpecificExpression<Expression::DropId> {
@@ -1070,6 +1076,32 @@ public:
   Pop(MixedArena& allocator) {}
 };
 
+class RefNull : public SpecificExpression<Expression::RefNullId> {
+public:
+  RefNull() = default;
+  RefNull(MixedArena& allocator) {}
+
+  void finalize();
+};
+
+class RefIsNull : public SpecificExpression<Expression::RefIsNullId> {
+public:
+  RefIsNull(MixedArena& allocator) {}
+
+  Expression* value;
+
+  void finalize();
+};
+
+class RefFunc : public SpecificExpression<Expression::RefFuncId> {
+public:
+  RefFunc(MixedArena& allocator) {}
+
+  Name func;
+
+  void finalize();
+};
+
 class Try : public SpecificExpression<Expression::TryId> {
 public:
   Try(MixedArena& allocator) {}