Don't use string slices when processing RexExp replace

src/runtime.cc

 // Copyright 2006-2009 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 1339 matching lines @@
     int length = to - from;
     ASSERT(length > 0);
     // Can we encode the slice in 11 bits for length and 19 bits for
     // start position - as used by StringBuilderConcatHelper?
     if (StringBuilderSubstringLength::is_valid(length) &&
         StringBuilderSubstringPosition::is_valid(from)) {
       int encoded_slice = StringBuilderSubstringLength::encode(length) |
           StringBuilderSubstringPosition::encode(from);
       AddElement(Smi::FromInt(encoded_slice));
     } else {
-      Handle<String> slice = Factory::NewStringSlice(subject_, from, to);
-      AddElement(*slice);
+      // Otherwise encode as two smis.
+      AddElement(Smi::FromInt(-length));
+      AddElement(Smi::FromInt(from));
     }
     IncrementCharacterCount(length);
   }
 
 
   void AddString(Handle<String> string) {
     int length = string->length();
     ASSERT(length > 0);
     AddElement(*string);
     if (!string->IsAsciiRepresentation()) {
@@ skipping 2387 matching lines @@
 
 template<typename sinkchar>
 static inline void StringBuilderConcatHelper(String* special,
                                              sinkchar* sink,
                                              FixedArray* fixed_array,
                                              int array_length) {
   int position = 0;
   for (int i = 0; i < array_length; i++) {
     Object* element = fixed_array->get(i);
     if (element->IsSmi()) {
+      // Smi encoding of position and length.
       int encoded_slice = Smi::cast(element)->value();
-      int pos = StringBuilderSubstringPosition::decode(encoded_slice);
-      int len = StringBuilderSubstringLength::decode(encoded_slice);
+      int pos;
+      int len;
+      if (encoded_slice > 0) {
+        // Position and length encoded in one smi.
+        pos = StringBuilderSubstringPosition::decode(encoded_slice);
+        len = StringBuilderSubstringLength::decode(encoded_slice);
+      } else {
+        // Position and length encoded in two smis.
+        Object* obj = fixed_array->get(++i);
+        ASSERT(obj->IsSmi());
+        pos = Smi::cast(obj)->value();
+        len = -encoded_slice;
+      }
       String::WriteToFlat(special,
                           sink + position,
                           pos,
                           pos + len);
       position += len;
     } else {
       String* string = String::cast(element);
       int element_length = string->length();
       String::WriteToFlat(string, sink + position, 0, element_length);
       position += element_length;
     }
   }
 }
 
 
 static Object* Runtime_StringBuilderConcat(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
   CONVERT_CHECKED(JSArray, array, args[0]);
   CONVERT_CHECKED(String, special, args[1]);
+
+  // This assumption is used by the slice encoding in one or two smis.
+  ASSERT(Smi::kMaxValue >= String::kMaxLength);
+
   int special_length = special->length();
   Object* smi_array_length = array->length();
   if (!smi_array_length->IsSmi()) {
     Top::context()->mark_out_of_memory();
     return Failure::OutOfMemoryException();
   }
   int array_length = Smi::cast(smi_array_length)->value();
   if (!array->HasFastElements()) {
     return Top::Throw(Heap::illegal_argument_symbol());
   }
   FixedArray* fixed_array = FixedArray::cast(array->elements());
   if (fixed_array->length() < array_length) {
     array_length = fixed_array->length();
   }
 
   if (array_length == 0) {
     return Heap::empty_string();
   } else if (array_length == 1) {
     Object* first = fixed_array->get(0);
     if (first->IsString()) return first;
   }
 
   bool ascii = special->IsAsciiRepresentation();
   int position = 0;
   for (int i = 0; i < array_length; i++) {
     Object* elt = fixed_array->get(i);
     if (elt->IsSmi()) {
+      // Smi encoding of position and length.
       int len = Smi::cast(elt)->value();
-      int pos = len >> 11;
-      len &= 0x7ff;
-      if (pos + len > special_length) {
-        return Top::Throw(Heap::illegal_argument_symbol());
+      if (len > 0) {
+        // Position and length encoded in one smi.
+        int pos = len >> 11;
+        len &= 0x7ff;
+        if (pos + len > special_length) {
+          return Top::Throw(Heap::illegal_argument_symbol());
+        }
+        position += len;
+      } else {
+        // Position and length encoded in two smis.
+        position += (-len);
+        // Get the position and check that it is also a smi.
+        i++;
+        if (i >= array_length) {
+          return Top::Throw(Heap::illegal_argument_symbol());
+        }
+        Object* pos = fixed_array->get(i);
+        if (!pos->IsSmi()) {
+          return Top::Throw(Heap::illegal_argument_symbol());
+        }
       }
-      position += len;
     } else if (elt->IsString()) {
       String* element = String::cast(elt);
       int element_length = element->length();
       position += element_length;
       if (ascii && !element->IsAsciiRepresentation()) {
         ascii = false;
       }
     } else {
       return Top::Throw(Heap::illegal_argument_symbol());
     }
@@ skipping 4016 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal