VM: Optimize RegExp.matchAsPrefix(...) by generating a sticky RegExp specialization.

runtime/vm/raw_object_snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
@@ skipping 2876 matching lines @@
 
   // Read and Set all the other fields.
   regex.StoreSmi(&regex.raw_ptr()->num_bracket_expressions_,
                  reader->ReadAsSmi());
   *reader->StringHandle() ^= reader->ReadObjectImpl(kAsInlinedObject);
   regex.set_pattern(*reader->StringHandle());
   regex.StoreNonPointer(&regex.raw_ptr()->num_registers_,
                         reader->Read<int32_t>());
   regex.StoreNonPointer(&regex.raw_ptr()->type_flags_, reader->Read<int8_t>());
 
   // TODO(18854): Need to implement a way of recreating the irrexp functions.

[rmacnak, 2016/11/17 00:49:52]

Remove this todo.

[Vyacheslav Egorov (Google), 2016/11/17 16:51:33]

Done.

   const Function& no_function = Function::Handle(reader->zone());
-  regex.set_function(kOneByteStringCid, no_function);
-  regex.set_function(kTwoByteStringCid, no_function);
-  regex.set_function(kExternalOneByteStringCid, no_function);
-  regex.set_function(kExternalTwoByteStringCid, no_function);
-
-  const TypedData& no_bytecode = TypedData::Handle(reader->zone());
-  regex.set_bytecode(true, no_bytecode);
-  regex.set_bytecode(false, no_bytecode);
+  for (intptr_t cid = kOneByteStringCid; cid <= kExternalTwoByteStringCid;

[erikcorry, 2016/11/17 13:56:17]

Here and elsewhere you put in a loop. Perhaps there should be kFirstStringCid
and kLastStringCid for use in loops, which are equal in value to the current
kOneByteStringCid and kExternalTwoByteStringCid.

[Vyacheslav Egorov (Google), 2016/11/17 16:51:33]

Yeah, that sounds like a nice improvement - but I will not do that as a part of
this CL.

+       cid++) {
+    regex.set_function(cid, /*sticky=*/false, no_function);
+    regex.set_function(cid, /*sticky=*/true, no_function);
+  }
 
   return regex.raw();
 }
 
 
 void RawRegExp::WriteTo(SnapshotWriter* writer,
                         intptr_t object_id,
                         Snapshot::Kind kind,
                         bool as_reference) {
   ASSERT(writer != NULL);
@@ skipping 95 matching lines @@
     // We do not allow objects with native fields in an isolate message.
     writer->SetWriteException(Exceptions::kArgument,
                               "Illegal argument in isolate message"
                               " : (object is a UserTag)");
   } else {
     UNREACHABLE();
   }
 }
 
 }  // namespace dart