Array.prototype.unshift builtin improvements

src/builtins.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/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 157 matching lines @@
 BUILTIN(Illegal) {
   UNREACHABLE();
   return isolate->heap()->undefined_value();  // Make compiler happy.
 }
 
 
 BUILTIN(EmptyFunction) {
   return isolate->heap()->undefined_value();
 }
 
+namespace {
 
-// TODO(cbruni): check if this is a suitable method on Object
-bool ClampedToInteger(Object* object, int* out) {
+bool ObjectToClampedInteger(Object* object, int* out) {
   // This is an extended version of ECMA-262 9.4, but additionally
   // clamps values to [kMinInt, kMaxInt]
   if (object->IsSmi()) {
     *out = Smi::cast(object)->value();
     return true;
   } else if (object->IsHeapNumber()) {
     *out = FastD2IChecked(HeapNumber::cast(object)->value());
     return true;
   } else if (object->IsUndefined()) {
     *out = 0;
@@ skipping 133 matching lines @@
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::Call(isolate,
                       function,
                       args.receiver(),
                       argc,
                       argv.start()));
   return *result;
 }
 
+}  // namespace
 
 BUILTIN(ArrayPush) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   MaybeHandle<FixedArrayBase> maybe_elms_obj =
       EnsureJSArrayWithWritableFastElements(isolate, receiver, &args, 1);
   Handle<FixedArrayBase> elms_obj;
   if (!maybe_elms_obj.ToHandle(&elms_obj)) {
     return CallJsBuiltin(isolate, "$arrayPush", args);
   }
@@ skipping 81 matching lines @@
       DisallowHeapAllocation no_gc;
       heap->MoveElements(*elms, 0, 1, len - 1);
       elms->set(len - 1, heap->the_hole_value());
     } else {
       Handle<FixedDoubleArray> elms = Handle<FixedDoubleArray>::cast(elms_obj);
       MoveDoubleElements(*elms, 0, *elms, 1, len - 1);
       elms->set_the_hole(len - 1);
     }
   }
 
-  // Set the length.
   array->set_length(Smi::FromInt(len - 1));
 
   return *first;
 }
 
 
 BUILTIN(ArrayUnshift) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   MaybeHandle<FixedArrayBase> maybe_elms_obj =
       EnsureJSArrayWithWritableFastElements(isolate, receiver, &args, 1);
   Handle<FixedArrayBase> elms_obj;
   if (!maybe_elms_obj.ToHandle(&elms_obj)) {
     return CallJsBuiltin(isolate, "$arrayUnshift", args);
   }
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
   DCHECK(!array->map()->is_observed());
-  if (!array->HasFastSmiOrObjectElements()) {
-    return CallJsBuiltin(isolate, "$arrayUnshift", args);
-  }
   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.
-  DCHECK(to_add <= (Smi::kMaxValue - len));
 
   if (to_add > 0 && JSArray::WouldChangeReadOnlyLength(array, len + to_add)) {
     return CallJsBuiltin(isolate, "$arrayUnshift", args);
   }
 
-  Handle<FixedArray> elms = Handle<FixedArray>::cast(elms_obj);
-
-  if (new_length > elms->length()) {
-    // New backing storage is needed.
-    int capacity = new_length + (new_length >> 1) + 16;
-    Handle<FixedArray> new_elms =
-        isolate->factory()->NewUninitializedFixedArray(capacity);
-
-    ElementsKind kind = array->GetElementsKind();
-    ElementsAccessor* accessor = array->GetElementsAccessor();
-    accessor->CopyElements(
-        elms, 0, kind, new_elms, to_add,
-        ElementsAccessor::kCopyToEndAndInitializeToHole);
-
-    elms = new_elms;
-    array->set_elements(*elms);
-  } else {
-    DisallowHeapAllocation no_gc;
-    Heap* heap = isolate->heap();
-    heap->MoveElements(*elms, to_add, 0, len);
-  }
-
-  // Add the provided values.
-  DisallowHeapAllocation no_gc;
-  WriteBarrierMode mode = elms->GetWriteBarrierMode(no_gc);
-  for (int i = 0; i < to_add; i++) {
-    elms->set(i, args[i + 1], mode);
-  }
-
-  // Set the length.
-  array->set_length(Smi::FromInt(new_length));
+  ElementsAccessor* accessor = array->GetElementsAccessor();
+  int new_length = accessor->Unshift(array, elms_obj, args, to_add);
   return Smi::FromInt(new_length);
 }
 
 
 BUILTIN(ArraySlice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   int len = -1;
   int relative_start = 0;
   int relative_end = 0;
@@ skipping 141 matching lines @@
   if (!maybe_elms_obj.ToHandle(&elms_obj)) {
     return CallJsBuiltin(isolate, "$arraySplice", args);
   }
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
   DCHECK(!array->map()->is_observed());
 
   int argument_count = args.length() - 1;
   int relative_start = 0;
   if (argument_count > 0) {
     DisallowHeapAllocation no_gc;
-    if (!ClampedToInteger(args[1], &relative_start)) {
+    if (!ObjectToClampedInteger(args[1], &relative_start)) {
       AllowHeapAllocation allow_allocation;
       return CallJsBuiltin(isolate, "$arraySplice", args);
     }
   }
   int len = Smi::cast(array->length())->value();
   // clip relative start to [0, len]
   int actual_start = (relative_start < 0) ? Max(len + relative_start, 0)
                                           : Min(relative_start, len);
 
   int actual_delete_count;
   if (argument_count == 1) {
     // SpiderMonkey, TraceMonkey and JSC treat the case where no delete count is
     // given as a request to delete all the elements from the start.
     // And it differs from the case of undefined delete count.
     // This does not follow ECMA-262, but we do the same for compatibility.
     DCHECK(len - actual_start >= 0);
     actual_delete_count = len - actual_start;
   } else {
     int delete_count = 0;
     DisallowHeapAllocation no_gc;
     if (argument_count > 1) {
-      if (!ClampedToInteger(args[2], &delete_count)) {
+      if (!ObjectToClampedInteger(args[2], &delete_count)) {
         AllowHeapAllocation allow_allocation;
         return CallJsBuiltin(isolate, "$arraySplice", args);
       }
     }
     actual_delete_count = Min(Max(delete_count, 0), len - actual_start);
   }
 
   int add_count = (argument_count > 1) ? (argument_count - 2) : 0;
   int new_length = len - actual_delete_count + add_count;
 
@@ skipping 704 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8