[ignition] desugar GetIterator() via bytecode rather than via AST

src/interpreter/bytecode-generator.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/interpreter/bytecode-generator.h"
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compilation-info.h"
@@ skipping 565 matching lines @@
       global_declarations_(0, info->zone()),
       function_literals_(0, info->zone()),
       native_function_literals_(0, info->zone()),
       execution_control_(nullptr),
       execution_context_(nullptr),
       execution_result_(nullptr),
       generator_resume_points_(info->literal()->yield_count(), info->zone()),
       generator_state_(),
       loop_depth_(0),
       home_object_symbol_(info->isolate()->factory()->home_object_symbol()),
+      iterator_symbol_(info->isolate()->factory()->iterator_symbol()),
       empty_fixed_array_(info->isolate()->factory()->empty_fixed_array()) {
   AstValueFactory* ast_value_factory = info->parse_info()->ast_value_factory();
   const AstRawString* prototype_string = ast_value_factory->prototype_string();
   ast_value_factory->Internalize(info->isolate());
   prototype_string_ = prototype_string->string();
 }
 
 Handle<BytecodeArray> BytecodeGenerator::FinalizeBytecode(Isolate* isolate) {
   AllocateDeferredConstants();
   if (HasStackOverflow()) return Handle<BytecodeArray>();
@@ skipping 2241 matching lines @@
   FeedbackVectorSlot slot = expr->BinaryOperationFeedbackSlot();
   builder()->BinaryOperation(expr->op(), lhs, feedback_index(slot));
 }
 
 void BytecodeGenerator::VisitSpread(Spread* expr) { Visit(expr->expression()); }
 
 void BytecodeGenerator::VisitEmptyParentheses(EmptyParentheses* expr) {
   UNREACHABLE();
 }
 
+void BytecodeGenerator::VisitGetIterator(GetIterator* expr) {
+  FeedbackVectorSlot load_slot = expr->IteratorPropertyFeedbackSlot();
+  FeedbackVectorSlot call_slot = expr->IteratorCallFeedbackSlot();
+
+  RegisterList args = register_allocator()->NewRegisterList(1);
+  Register method = register_allocator()->NewRegister();
+  Register obj = args[0];
+
+  VisitForAccumulatorValue(expr->iterable());
+
+  // Let method be ? GetMethod(obj, @@iterator).

[rmcilroy, 2016/12/06 15:02:28]

Not sure what the "?" means here. Can we just remove it?

[caitp, 2016/12/06 15:14:58]

It's the spec's short form for "ReturnIfAbrupt(<completion>)", basically just
means the op can throw. Fine to remove it

[rmcilroy, 2016/12/07 10:50:41]

Yeah I would rather we remove it (and add the comment about calling it as Georg
mentioned below).

+  builder()

[neis, 2016/12/07 10:17:27]

Please change the comment to reflect that the result is also called.

+      ->StoreAccumulatorInRegister(obj)
+      .LoadNamedProperty(obj, iterator_symbol(), feedback_index(load_slot))
+      .StoreAccumulatorInRegister(method)
+      .Call(method, args, feedback_index(call_slot), Call::NAMED_PROPERTY_CALL);
+
+  // If Type(iterator) is not Object, throw a TypeError exception.
+  BytecodeLabel no_type_error;
+  builder()->JumpIfJSReceiver(&no_type_error);
+  builder()->CallRuntime(Runtime::kThrowSymbolIteratorInvalid);
+  builder()->Bind(&no_type_error);
+}
+
 void BytecodeGenerator::VisitThisFunction(ThisFunction* expr) {
   builder()->LoadAccumulatorWithRegister(Register::function_closure());
 }
 
 void BytecodeGenerator::VisitSuperCallReference(SuperCallReference* expr) {
   // Handled by VisitCall().
   UNREACHABLE();
 }
 
 void BytecodeGenerator::VisitSuperPropertyReference(
@@ skipping 366 matching lines @@
 }
 
 Runtime::FunctionId BytecodeGenerator::StoreKeyedToSuperRuntimeId() {
   return is_strict(language_mode()) ? Runtime::kStoreKeyedToSuper_Strict
                                     : Runtime::kStoreKeyedToSuper_Sloppy;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8