For-of calls [Symbol.iterator]() on RHS to get iterator

src/x64/full-codegen-x64.cc

 // Copyright 2012 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/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 1234 matching lines @@
 }
 
 
 void FullCodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
   Comment cmnt(masm_, "[ ForOfStatement");
   SetStatementPosition(stmt);
 
   Iteration loop_statement(this, stmt);
   increment_loop_depth();
 
-  // var iterator = iterable[@@iterator]()
-  VisitForAccumulatorValue(stmt->assign_iterator());
+  // var iterable = subject
+  VisitForAccumulatorValue(stmt->assign_iterable());
 
-  // As with for-in, skip the loop if the iterator is null or undefined.
+  // As with for-in, skip the loop if the iterable is null or undefined.
   __ CompareRoot(rax, Heap::kUndefinedValueRootIndex);
   __ j(equal, loop_statement.break_label());
   __ CompareRoot(rax, Heap::kNullValueRootIndex);
   __ j(equal, loop_statement.break_label());
 
-  // Convert the iterator to a JS object.
-  Label convert, done_convert;
-  __ JumpIfSmi(rax, &convert);
-  __ CmpObjectType(rax, FIRST_SPEC_OBJECT_TYPE, rcx);
-  __ j(above_equal, &done_convert);
-  __ bind(&convert);
-  __ Push(rax);
-  __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
-  __ bind(&done_convert);
+  // var iterator = iterable[Symbol.iterator]();
+  VisitForEffect(stmt->assign_iterator());
 
   // Loop entry.
   __ bind(loop_statement.continue_label());
 
   // result = iterator.next()
   VisitForEffect(stmt->next_result());
 
   // if (result.done) break;
   Label result_not_done;
   VisitForControl(stmt->result_done(),
@@ skipping 3527 matching lines @@
   ASSERT_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64