Various species micro-optimizations

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-arguments.h"
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/base/once.h"
@@ skipping 540 matching lines @@
 BUILTIN(ArraySlice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
   int len = -1;
   int relative_start = 0;
   int relative_end = 0;
 
   if (receiver->IsJSArray()) {
     DisallowHeapAllocation no_gc;
     JSArray* array = JSArray::cast(*receiver);
-    if (!array->HasFastElements() ||
-        !IsJSArrayFastElementMovingAllowed(isolate, array) ||
-        !isolate->IsArraySpeciesLookupChainIntact() ||
-        // If this is a subclass of Array, then call out to JS
-        !array->HasArrayPrototype(isolate)) {
+    if (V8_UNLIKELY(!array->HasFastElements() ||
+                    !IsJSArrayFastElementMovingAllowed(isolate, array) ||
+                    !isolate->IsArraySpeciesLookupChainIntact() ||
+                    // If this is a subclass of Array, then call out to JS
+                    !array->HasArrayPrototype(isolate))) {
       AllowHeapAllocation allow_allocation;
       return CallJsIntrinsic(isolate, isolate->array_slice(), args);
     }
     len = Smi::cast(array->length())->value();
   } else if (receiver->IsJSObject() &&
              GetSloppyArgumentsLength(isolate, Handle<JSObject>::cast(receiver),
                                       &len)) {
     // Array.prototype.slice.call(arguments, ...) is quite a common idiom
     // (notably more than 50% of invocations in Web apps).
     // Treat it in C++ as well.
@@ skipping 38 matching lines @@
 
   Handle<JSObject> object = Handle<JSObject>::cast(receiver);
   ElementsAccessor* accessor = object->GetElementsAccessor();
   return *accessor->Slice(object, actual_start, actual_end);
 }
 
 
 BUILTIN(ArraySplice) {
   HandleScope scope(isolate);
   Handle<Object> receiver = args.receiver();
-  if (!EnsureJSArrayWithWritableFastElements(isolate, receiver, &args, 3) ||
-      // If this is a subclass of Array, then call out to JS.
-      !Handle<JSArray>::cast(receiver)->HasArrayPrototype(isolate) ||
-      // If anything with @@species has been messed with, call out to JS.
-      !isolate->IsArraySpeciesLookupChainIntact()) {
+  if (V8_UNLIKELY(
+          !EnsureJSArrayWithWritableFastElements(isolate, receiver, &args, 3) ||
+          // If this is a subclass of Array, then call out to JS.
+          !Handle<JSArray>::cast(receiver)->HasArrayPrototype(isolate) ||
+          // If anything with @@species has been messed with, call out to JS.
+          !isolate->IsArraySpeciesLookupChainIntact())) {
     return CallJsIntrinsic(isolate, isolate->array_splice(), args);
   }
   Handle<JSArray> array = Handle<JSArray>::cast(receiver);
 
   int argument_count = args.length() - 1;
   int relative_start = 0;
   if (argument_count > 0) {
     DisallowHeapAllocation no_gc;
     if (!ClampedToInteger(args[1], &relative_start)) {
       AllowHeapAllocation allow_allocation;
@@ skipping 845 matching lines @@
         isolate, NewTypeError(MessageTemplate::kCalledOnNullOrUndefined,
                               isolate->factory()->NewStringFromAsciiChecked(
                                   "Array.prototype.concat")));
   }
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, receiver, Object::ToObject(isolate, args.receiver()));
   args[0] = *receiver;
 
   Handle<JSArray> result_array;
 
+  // Avoid a real species read to avoid extra lookups to the array constructor
+  if (V8_LIKELY(receiver->IsJSArray() &&
+                Handle<JSArray>::cast(receiver)->HasArrayPrototype(isolate) &&
+                isolate->IsArraySpeciesLookupChainIntact())) {
+    if (Fast_ArrayConcat(isolate, &args).ToHandle(&result_array)) {
+      return *result_array;
+    }
+    if (isolate->has_pending_exception()) return isolate->heap()->exception();
+  }
   // Reading @@species happens before anything else with a side effect, so
   // we can do it here to determine whether to take the fast path.
   Handle<Object> species;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, species, Object::ArraySpeciesConstructor(isolate, receiver));
-  if (*species == isolate->context()->native_context()->array_function()) {
+  if (*species == *isolate->array_function()) {
     if (Fast_ArrayConcat(isolate, &args).ToHandle(&result_array)) {
       return *result_array;
     }
     if (isolate->has_pending_exception()) return isolate->heap()->exception();
   }
   return Slow_ArrayConcat(&args, species, isolate);
 }
 
 
 namespace {
@@ skipping 3946 matching lines @@
 BUILTIN_LIST_T(DEFINE_BUILTIN_ACCESSOR_T)
 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
 #undef DEFINE_BUILTIN_ACCESSOR_T
 #undef DEFINE_BUILTIN_ACCESSOR_H
 
 }  // namespace internal
 }  // namespace v8