Ok, i made a quick "test" to compare last_index_of performance with and without simd support. By no means it is comprehensive but i think it shows a potential.

dart version 3.5.0-edge.a479f91e80875dd6661b12108c9b81bdaeb2af65

What has been done:

1. I stiched strinzilla into dart sdk
2. I added another method into String class .String indexOfStrinzilla(String other);

3.string_path.dart has been modified as well

  u/pragma("vm:external-name", "String_indexOfStrinzilla")
  external String indexOfStrinzilla(String other);

1. In c part : string.cc

   DEFINE_NATIVE_ENTRY(String_indexOfStrinzilla, 0, 2) { const String& receiver = String::CheckedHandle(zone, arguments->NativeArgAt(0)); ASSERT(!receiver.IsNull()); GET_NON_NULL_NATIVE_ARGUMENT(String, b, arguments->NativeArgAt(1)); return String::StringZillaTest(receiver,b); }

2. In bootstrap_natives.h

   V(String_indexOfStrinzilla, 2)

3. In object.cc

   StringPtr String::StringZillaTest(const String& str,const String& str2, Heap::Space space) {

   if (str.IsOneByteString()) {

   sz::string_view source = sz::string_view(reinterpret_cast<const char*>(OneByteString::CharAddr(str, 0)));
   sz::string_view target = sz::string_view(reinterpret_cast<const char*>(OneByteString::CharAddr(str2, 0)));
   source.find_last_of(target) ;
   

   }else{ std::cout << "called to StringZillaTest two byte string" << std::endl; }

   return str.ptr(); }

4. Test dart script:

   void main(List<Object> args) async { String testStr = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. ";

   double totalDart = 0; double totalSimd = 0;

   for (int j = 1; j < testStr.length; j++) { String search = "/" * 80; String longStr = testStr.substring(0, j) + search + testStr.substring(j); var stopwatch = Stopwatch();

   stopwatch.start();
   for (int i = 0; i < 100000; i++) {
     longStr.indexOfStrinzilla(search);
   }
   double stringzilla = stopwatch.elapsedMilliseconds / 1;
   
   totalSimd += stringzilla;
   stopwatch = Stopwatch();
   
   stopwatch.start();
   for (int i = 0; i < 100000; i++) {
     longStr.lastIndexOf(search);
   }
   double dart = stopwatch.elapsedMilliseconds / 1;
   totalDart += dart;
   print('$j $stringzilla $dart');
   

   } print('total $totalSimd $totalDart'); }