Generators return boxed values

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index 0ef4be064dac2b7b049c8fdf967a659e190275c8..21edccac18a7daa401415f0b9c3d5c7e13be8ff3 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -1939,11 +1939,12 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       Label resume;
       __ CompareRoot(result_register(), Heap::kTheHoleValueRootIndex);
       __ b(ne, &resume);
-      __ pop(result_register());
       if (expr->yield_kind() == Yield::SUSPEND) {
-        // TODO(wingo): Box into { value: VALUE, done: false }.
+        EmitReturnIteratorResult(false);
+      } else {
+        __ pop(result_register());
+        EmitReturnSequence();
       }
-      EmitReturnSequence();
 
       __ bind(&resume);
       context()->Plug(result_register());
@@ -1955,18 +1956,7 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ mov(r1, Operand(Smi::FromInt(JSGeneratorObject::kGeneratorClosed)));
       __ str(r1, FieldMemOperand(result_register(),
                                  JSGeneratorObject::kContinuationOffset));
-      __ pop(result_register());
-      // TODO(wingo): Box into { value: VALUE, done: true }.
-
-      // Exit all nested statements.
-      NestedStatement* current = nesting_stack_;
-      int stack_depth = 0;
-      int context_length = 0;
-      while (current != NULL) {
-        current = current->Exit(&stack_depth, &context_length);
-      }
-      __ Drop(stack_depth);
-      EmitReturnSequence();
+      EmitReturnIteratorResult(true);
       break;
     }
 
@@ -2074,6 +2064,63 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
 }
 
 
+void FullCodeGenerator::EmitReturnIteratorResult(bool done) {
+  Label gc_required;
+  Label allocated;
+
+  STATIC_ASSERT(HeapObject::kMapOffset == 0);
+  STATIC_ASSERT(JSObject::kPropertiesOffset == kPointerSize);
+  STATIC_ASSERT(JSObject::kElementsOffset == 2 * kPointerSize);
+  STATIC_ASSERT(JSObject::kHeaderSize == 3 * kPointerSize);
+  STATIC_ASSERT(JSGeneratorObject::kResultValuePropertyIndex == 0);
+  STATIC_ASSERT(JSGeneratorObject::kResultDonePropertyIndex == 1);
+
+  const int size = 5 * kPointerSize;
+  __ Allocate(size, r0, r2, r3, &gc_required, TAG_OBJECT);
+
+  __ bind(&allocated);
+  // The object is now in r0.  Initialize its map, value, and done fields.
+  Handle<Map> map(isolate()->native_context()->iterator_result_map());
+  __ mov(r1, Operand(map));
+  __ pop(r2);
+  __ mov(r3,
+         done
+         ? Operand(isolate()->factory()->true_value())
+         : Operand(isolate()->factory()->false_value()));
+  __ mov(r4, Operand(isolate()->factory()->empty_fixed_array()));
+  __ str(r1, FieldMemOperand(r0, 0 * kPointerSize));  // map
+  __ str(r4, FieldMemOperand(r0, 1 * kPointerSize));  // properties
+  __ str(r4, FieldMemOperand(r0, 2 * kPointerSize));  // elements
+  __ str(r2, FieldMemOperand(r0, 3 * kPointerSize));  // value
+  __ str(r3, FieldMemOperand(r0, 4 * kPointerSize));  // done?
+
+  // Only the value field needs a write barrier, as the other values are in the
+  // root set.
+  __ RecordWriteField(r0, 3 * kPointerSize, r2, r3,
+                      kLRHasBeenSaved, kDontSaveFPRegs);
+
+  if (done) {
+    // Exit all nested statements.
+    NestedStatement* current = nesting_stack_;
+    int stack_depth = 0;
+    int context_length = 0;
+    while (current != NULL) {
+      current = current->Exit(&stack_depth, &context_length);
+    }
+    __ Drop(stack_depth);
+  }
+
+  EmitReturnSequence();
+
+  __ bind(&gc_required);
+  __ Push(Smi::FromInt(size));
+  __ CallRuntime(Runtime::kAllocateInNewSpace, 1);
+  __ ldr(context_register(),
+         MemOperand(fp, StandardFrameConstants::kContextOffset));
+  __ jmp(&allocated);
+}
+
+
 void FullCodeGenerator::EmitNamedPropertyLoad(Property* prop) {
   SetSourcePosition(prop->position());
   Literal* key = prop->key()->AsLiteral();