Attempt at pre-calculating replace regexp matches.

src/objects-inl.h

 // 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 3007 matching lines @@
 
 void Map::ClearCodeCache() {
   // No write barrier is needed since empty_fixed_array is not in new space.
   // Please note this function is used during marking:
   //  - MarkCompactCollector::MarkUnmarkedObject
   ASSERT(!Heap::InNewSpace(Heap::raw_unchecked_empty_fixed_array()));
   WRITE_FIELD(this, kCodeCacheOffset, Heap::raw_unchecked_empty_fixed_array());
 }
 
 
+void JSArray::Resize(int required_size) {
+  ASSERT(HasFastElements());
+  int current_length = Smi::cast(this->length())->value();
+  Array* elts = elements();
+  if (required_size < current_length) {
+    // Set length before potentially expanding. If a new backing array is
+    // allocated, we will only copy the data below the new length.
+    this->set_length(Smi::FromInt(required_size));
+  }
+  const int kArraySizeThatFitsComfortablyInNewSpace = 128;
+  if (elts->length() < required_size) {
+    // Doubling in size would be overkill, but leave some slack to avoid
+    // constantly growing.
+    Expand(required_size + (required_size >> 3));
+    // It's a performance benefit to keep a frequently used array in new-space.
+  } else if (!Heap::InNewSpace(elts) &&
+             required_size < kArraySizeThatFitsComfortablyInNewSpace) {
+    // Expand will allocate a new backing store in new space even if the size
+    // we asked for isn't larger than what we had before.
+    Expand(required_size);
+  } else {
+    // Using same backing store.
+    if (current_length > required_size) {
+      for (int i = required_size; i < current_length; i++) {
+        FixedArray::cast(elts)->set_the_hole(i);
+      }
+      return;
+    }
+  }
+}
+
+
 void JSArray::EnsureSize(int required_size) {
   ASSERT(HasFastElements());
   Array* elts = elements();
   const int kArraySizeThatFitsComfortablyInNewSpace = 128;
   if (elts->length() < required_size) {
     // Doubling in size would be overkill, but leave some slack to avoid
     // constantly growing.
     Expand(required_size + (required_size >> 3));
     // It's a performance benefit to keep a frequently used array in new-space.
   } else if (!Heap::new_space()->Contains(elts) &&
@@ skipping 39 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_