Revert "More generic version of Array.concat builtin."

src/builtins.cc

 // Copyright 2006-2008 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 710 matching lines @@
   }
 
   // Set the length.
   array->set_length(Smi::FromInt(new_length));
 
   return result_array;
 }
 
 
 BUILTIN(ArrayConcat) {
-  if (!ArrayPrototypeHasNoElements()) {
+  Counters::array_concat_builtin_total.Increment();
+  if (args.length() != 2) {
+    // Fast case only for concating two arrays.
+    return CallJsBuiltin("ArrayConcat", args);
+  }
+  Counters::array_concat_builtin_two_args.Increment();
+
+  Object* receiver_obj = *args.receiver();
+  FixedArray* receiver_elms = NULL;
+  Object* arg_obj = args[1];
+  FixedArray* arg_elms = NULL;
+  if (!IsJSArrayWithFastElements(receiver_obj, &receiver_elms)
+      || !IsJSArrayWithFastElements(arg_obj, &arg_elms)
+      || !ArrayPrototypeHasNoElements()) {
     return CallJsBuiltin("ArrayConcat", args);
   }
 
-  // Iterate through all the arguments performing checks
-  // and calculating total length.
-  int n_arguments = args.length();
-  int result_len = 0;
-  for (int i = 0; i < n_arguments; i++) {
-    Object* arg = args[i];
-    if (!arg->IsJSArray() || JSArray::cast(arg)->HasFastElements()) {
-      return CallJsBuiltin("ArrayConcat", args);
-    }
+  JSArray* receiver_array = JSArray::cast(receiver_obj);
+  ASSERT(receiver_array->HasFastElements());
+  JSArray* arg_array = JSArray::cast(arg_obj);
+  ASSERT(arg_array->HasFastElements());
 
-    int len = Smi::cast(JSArray::cast(arg)->length())->value();
+  int receiver_len = Smi::cast(receiver_array->length())->value();
+  int arg_len = Smi::cast(arg_array->length())->value();
+  ASSERT(receiver_len <= (Smi::kMaxValue - arg_len));
 
-    // We shouldn't overflow when adding another len.
-    const int kHalfOfMaxInt = 1 << (kBitsPerInt - 2);
-    STATIC_ASSERT(FixedArray::kMaxLength < kHalfOfMaxInt);
-    USE(kHalfOfMaxInt);
-    result_len += len;
-    ASSERT(result_len >= 0);
-
-    if (result_len > FixedArray::kMaxLength) {
-      return CallJsBuiltin("ArrayConcat", args);
-    }
+  int result_len = receiver_len + arg_len;
+  if (result_len > FixedArray::kMaxSize) {
+    return CallJsBuiltin("ArrayConcat", args);
   }
-
   if (result_len == 0) {
     return AllocateEmptyJSArray();
   }
 
   // Allocate result.
   Object* result = AllocateJSArray();
   if (result->IsFailure()) return result;
   JSArray* result_array = JSArray::cast(result);
 
   result = Heap::AllocateUninitializedFixedArray(result_len);
   if (result->IsFailure()) return result;
   FixedArray* result_elms = FixedArray::cast(result);
 
   // Copy data.
   AssertNoAllocation no_gc;
-  int start_pos = 0;
-  for (int i = 0; i < n_arguments; i++) {
-    JSArray* array = JSArray::cast(args[i]);
-    FixedArray* elms = FixedArray::cast(array->elements());
-    int len = Smi::cast(array->length())->value();
-    CopyElements(&no_gc, result_elms, start_pos, elms, 0, len);
-    start_pos += len;
-  }
-  ASSERT(start_pos == result_len);
+  CopyElements(&no_gc, result_elms, 0, receiver_elms, 0, receiver_len);
+  CopyElements(&no_gc, result_elms, receiver_len, arg_elms, 0, arg_len);
 
   // Set the length and elements.
   result_array->set_length(Smi::FromInt(result_len));
   result_array->set_elements(result_elms);
 
   return result_array;
 }
 
 
 // -----------------------------------------------------------------------------
@@ skipping 639 matching lines @@
       if (entry->contains(pc)) {
         return names_[i];
       }
     }
   }
   return NULL;
 }
 
 
 } }  // namespace v8::internal