Support Smi->Double->HeapObject transitions in constructed Arrays.

src/builtins.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 215 matching lines @@
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
     return array->SetElementsLength(args[1]);
   }
 
   // Optimize the case where there are no parameters passed.
   if (args.length() == 1) {
     return array->Initialize(JSArray::kPreallocatedArrayElements);
   }
 
-  // Take the arguments as elements.
+  // Set length and elements on the array.
   int number_of_elements = args.length() - 1;
-  Smi* len = Smi::FromInt(number_of_elements);
+  array->set_length(Smi::FromInt(0));

[Jakob Kummerow, 2011/12/07 17:02:47]

A comment explaining why the length must be set to 0 first would be nice.

[danno, 2011/12/08 15:09:09]

It's actually unneeded. Removed.
On 2011/12/07 17:02:47, Jakob wrote:

+  MaybeObject* maybe_object =
+      array->EnsureCanContainElements(&args, 1, number_of_elements,
+                                      ALLOW_CONVERTED_DOUBLE_ELEMENTS);
+  if (maybe_object->IsFailure()) return maybe_object;
+
+  // Allocate an appropriately typed elements array.
   Object* obj;
-  { MaybeObject* maybe_obj = heap->AllocateFixedArrayWithHoles(len->value());
-    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  MaybeObject* maybe_obj;
+  ElementsKind elements_kind = array->GetElementsKind();
+  if (elements_kind == FAST_DOUBLE_ELEMENTS) {
+    maybe_obj = heap->AllocateUninitializedFixedDoubleArray(
+        number_of_elements);
+  } else {
+    maybe_obj = heap->AllocateFixedArrayWithHoles(number_of_elements);
+  }
+  if (!maybe_obj->ToObject(&obj)) return maybe_obj;
+  FixedArrayBase* elms = FixedArrayBase::cast(obj);

[Jakob Kummerow, 2011/12/07 17:02:47]

Thanks to templates, you can clean this up a little by writing:
if (!maybe_obj->To(&elms)) return maybe_obj;
Then you wouldn't need "Object* obj;" at all. I don't mind either way, your
call.

[danno, 2011/12/08 15:09:09]

Done.

+
+  // Fill in the content
+  switch (array->GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS: {
+      FixedArray* smi_elms = FixedArray::cast(elms);
+      for (int index = 0; index < number_of_elements; index++) {
+        smi_elms->set(index, args[index+1], SKIP_WRITE_BARRIER);
+      }
+      break;
+    }
+    case FAST_ELEMENTS: {
+      AssertNoAllocation no_gc;
+      WriteBarrierMode mode = elms->GetWriteBarrierMode(no_gc);
+      FixedArray* object_elms = FixedArray::cast(elms);
+      for (int index = 0; index < number_of_elements; index++) {
+        object_elms->set(index, args[index+1], mode);
+      }
+      break;
+    }
+    case FAST_DOUBLE_ELEMENTS: {
+      FixedDoubleArray* double_elms = FixedDoubleArray::cast(elms);
+      for (int index = 0; index < number_of_elements; index++) {
+        double_elms->set(index, args[index+1]->Number());
+      }
+      break;
+    }
+    default:
+      UNREACHABLE();
+      break;
   }
 
-  // Set length and elements on the array.
-  MaybeObject* maybe_object =
-      array->EnsureCanContainElements(FixedArray::cast(obj));
-  if (maybe_object->IsFailure()) return maybe_object;
-
-  AssertNoAllocation no_gc;
-  FixedArray* elms = FixedArray::cast(obj);
-  WriteBarrierMode mode = elms->GetWriteBarrierMode(no_gc);
-  // Fill in the content
-  for (int index = 0; index < number_of_elements; index++) {
-    elms->set(index, args[index+1], mode);
-  }
-
-  array->set_elements(FixedArray::cast(obj));
-  array->set_length(len);
-
+  array->set_elements(elms);
+  array->set_length(Smi::FromInt(number_of_elements));
   return array;
 }
 
 
 MUST_USE_RESULT static MaybeObject* AllocateJSArray(Heap* heap) {
   JSFunction* array_function =
       heap->isolate()->context()->global_context()->array_function();
   Object* result;
   { MaybeObject* maybe_result = heap->AllocateJSObject(array_function);
     if (!maybe_result->ToObject(&result)) return maybe_result;
@@ skipping 147 matching lines @@
   }
 
   // Need to ensure that the arguments passed in args can be contained in
   // the array.
   int args_length = args->length();
   if (first_added_arg >= args_length) return array->elements();
 
   MaybeObject* maybe_array = array->EnsureCanContainElements(
       args,
       first_added_arg,
-      args_length - first_added_arg);
+      args_length - first_added_arg,
+      DONT_ALLOW_DOUBLE_ELEMENTS);
   if (maybe_array->IsFailure()) return maybe_array;
   return array->elements();
 }
 
 
 static inline bool IsJSArrayFastElementMovingAllowed(Heap* heap,
                                                      JSArray* receiver) {
   if (!FLAG_clever_optimizations) return false;
   Context* global_context = heap->isolate()->context()->global_context();
   JSObject* array_proto =
@@ skipping 182 matching lines @@
   ASSERT(array->HasFastTypeElements());
 
   int len = Smi::cast(array->length())->value();
   int to_add = args.length() - 1;
   int new_length = len + to_add;
   // Currently fixed arrays cannot grow too big, so
   // we should never hit this case.
   ASSERT(to_add <= (Smi::kMaxValue - len));
 
   MaybeObject* maybe_object =
-      array->EnsureCanContainElements(&args, 1, to_add);
+      array->EnsureCanContainElements(&args, 1, to_add,
+                                      DONT_ALLOW_DOUBLE_ELEMENTS);
   if (maybe_object->IsFailure()) return maybe_object;
 
   if (new_length > elms->length()) {
     // New backing storage is needed.
     int capacity = new_length + (new_length >> 1) + 16;
     Object* obj;
     { MaybeObject* maybe_obj = heap->AllocateUninitializedFixedArray(capacity);
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
     FixedArray* new_elms = FixedArray::cast(obj);
@@ skipping 110 matching lines @@
   }
   JSArray* result_array = JSArray::cast(result);
 
   { MaybeObject* maybe_result =
         heap->AllocateUninitializedFixedArray(result_len);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   FixedArray* result_elms = FixedArray::cast(result);
 
   MaybeObject* maybe_object =
-      result_array->EnsureCanContainElements(result_elms);
+      result_array->EnsureCanContainElements(result_elms,
+                                             DONT_ALLOW_DOUBLE_ELEMENTS);
   if (maybe_object->IsFailure()) return maybe_object;
 
   AssertNoAllocation no_gc;
   CopyElements(heap, &no_gc, result_elms, 0, elms, k, result_len);
 
   // Set elements.
   result_array->set_elements(result_elms);
 
   // Set the length.
   result_array->set_length(Smi::FromInt(result_len));
@@ skipping 243 matching lines @@
         heap->AllocateUninitializedFixedArray(result_len);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   FixedArray* result_elms = FixedArray::cast(result);
 
   // Ensure element type transitions happen before copying elements in.
   if (result_array->HasFastSmiOnlyElements()) {
     for (int i = 0; i < n_arguments; i++) {
       JSArray* array = JSArray::cast(args[i]);
       if (!array->HasFastSmiOnlyElements()) {
-        result_array->EnsureCanContainNonSmiElements();
+        result_array->EnsureCanContainHeapObjectElements();
         break;
       }
     }
   }
 
   // Copy data.
   AssertNoAllocation no_gc;
   int start_pos = 0;
   for (int i = 0; i < n_arguments; i++) {
     JSArray* array = JSArray::cast(args[i]);
@@ skipping 749 matching lines @@
   return Handle<Code>(code_address);                        \
 }
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 } }  // namespace v8::internal