Refactored code a bit to improve StringReplace performance

src/zone.cc

 // Copyright 2012 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 74 matching lines @@
 }
 
 
 void Zone::DeleteAll() {
 #ifdef DEBUG
   // Constant byte value used for zapping dead memory in debug mode.
   static const unsigned char kZapDeadByte = 0xcd;
 #endif
 
   // Find a segment with a suitable size to keep around.
-  Segment* keep = segment_head_;
-  while (keep != NULL && keep->size() > kMaximumKeptSegmentSize) {
-    keep = keep->next();
-  }
-
+  Segment* keep = NULL;
   // Traverse the chained list of segments, zapping (in debug mode)
   // and freeing every segment except the one we wish to keep.
   for (Segment* current = segment_head_; current != NULL; ) {
     Segment* next = current->next();
-    if (current == keep) {
+    if (keep == NULL && current->size() <= kMaximumKeptSegmentSize) {
       // Unlink the segment we wish to keep from the list.
-      current->clear_next();
+      keep = current;
+      keep->clear_next();
     } else {
       int size = current->size();
 #ifdef DEBUG
       // Zap the entire current segment (including the header).
       memset(current, kZapDeadByte, size);
 #endif
       DeleteSegment(current, size);
     }
     current = next;
   }
@@ skipping 103 matching lines @@
     V8::FatalProcessOutOfMemory("Zone");
     return NULL;
   }
   limit_ = segment->end();
   ASSERT(position_ <= limit_);
   return result;
 }
 
 
 } }  // namespace v8::internal