[generators] Store the resume mode in the generator object.

src/full-codegen/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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 1766 matching lines @@
   SetExpressionPosition(expr);
 
   // Evaluate yielded value first; the initial iterator definition depends on
   // this.  It stays on the stack while we update the iterator.
   VisitForStackValue(expr->expression());
 
   Label suspend, continuation, post_runtime, resume, exception;
 
   __ jmp(&suspend);
   __ bind(&continuation);
-  // When we arrive here, the stack top is the resume mode and
-  // result_register() holds the input value (the argument given to the
-  // respective resume operation).
+  // When we arrive here, rax holds the generator object.
   __ RecordGeneratorContinuation();
-  __ Pop(rbx);
+  __ movp(rbx, FieldOperand(rax, JSGeneratorObject::kResumeModeOffset));
+  __ movp(rax, FieldOperand(rax, JSGeneratorObject::kInputOffset));
   STATIC_ASSERT(JSGeneratorObject::kNext < JSGeneratorObject::kReturn);
   STATIC_ASSERT(JSGeneratorObject::kThrow > JSGeneratorObject::kReturn);
   __ SmiCompare(rbx, Smi::FromInt(JSGeneratorObject::kReturn));
   __ j(less, &resume);
   __ Push(result_register());
   __ j(greater, &exception);
   EmitCreateIteratorResult(true);
   EmitUnwindAndReturn();
 
   __ bind(&exception);
@@ skipping 2078 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64