[async-iteration] add support for for-await-of loops in Async Functions

src/ast/ast.h

Index: src/ast/ast.h
diff --git a/src/ast/ast.h b/src/ast/ast.h
index 9a87328a7b98ad1cb1fc62a9da26d03d1fdfc5cd..553725c8a5a38372e7aa26ff48cc29a89efa47fa 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -2965,8 +2965,13 @@ class EmptyParentheses final : public Expression {
 // (defined at https://tc39.github.io/ecma262/#sec-getiterator). Ignition
 // desugars this into a LoadIC / JSLoadNamed, CallIC, and a type-check to
 // validate return value of the Symbol.iterator() call.
+enum class IteratorType { kNormal, kAsync };
 class GetIterator final : public Expression {
  public:
+  using Hint = IteratorType;
+
+  Hint hint() const { return hint_; }
+
   Expression* iterable() const { return iterable_; }
   void set_iterable(Expression* iterable) { iterable_ = iterable; }
 
@@ -2978,6 +2983,14 @@ class GetIterator final : public Expression {
         spec->AddSlot(FeedbackVectorSlotKind::LOAD_IC);
     iterator_call_feedback_slot_ =
         spec->AddSlot(FeedbackVectorSlotKind::CALL_IC);
+
+    if (hint() == Hint::kAsync) {
+      // Can we just re-use the other slots?
+      async_iterator_property_feedback_slot_ =
+          spec->AddSlot(FeedbackVectorSlotKind::LOAD_IC);
+      async_iterator_call_feedback_slot_ =
+          spec->AddSlot(FeedbackVectorSlotKind::CALL_IC);
+    }
   }
 
   FeedbackVectorSlot IteratorPropertyFeedbackSlot() const {
@@ -2988,15 +3001,26 @@ class GetIterator final : public Expression {
     return iterator_call_feedback_slot_;
   }
 
+  FeedbackVectorSlot AsyncIteratorPropertyFeedbackSlot() const {
+    return async_iterator_property_feedback_slot_;
+  }
+
+  FeedbackVectorSlot AsyncIteratorCallFeedbackSlot() const {
+    return async_iterator_call_feedback_slot_;
+  }
+
  private:
   friend class AstNodeFactory;
 
-  explicit GetIterator(Expression* iterable, int pos)
-      : Expression(pos, kGetIterator), iterable_(iterable) {}
+  explicit GetIterator(Expression* iterable, Hint hint, int pos)
+      : Expression(pos, kGetIterator), hint_(hint), iterable_(iterable) {}
 
+  Hint hint_;
   Expression* iterable_;
   FeedbackVectorSlot iterator_property_feedback_slot_;
   FeedbackVectorSlot iterator_call_feedback_slot_;
+  FeedbackVectorSlot async_iterator_property_feedback_slot_;
+  FeedbackVectorSlot async_iterator_call_feedback_slot_;
 };
 
 // ----------------------------------------------------------------------------
@@ -3576,8 +3600,9 @@ class AstNodeFactory final BASE_EMBEDDED {
     return new (zone_) EmptyParentheses(pos);
   }
 
-  GetIterator* NewGetIterator(Expression* iterable, int pos) {
-    return new (zone_) GetIterator(iterable, pos);
+  GetIterator* NewGetIterator(Expression* iterable, GetIterator::Hint hint,
+                              int pos) {
+    return new (zone_) GetIterator(iterable, hint, pos);
   }
 
   Zone* zone() const { return zone_; }