[regexp] Port RegExpExecStub to CSA (mostly)

src/runtime/runtime-regexp.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/conversions-inl.h"
 #include "src/isolate-inl.h"
 #include "src/messages.h"
@@ skipping 1637 matching lines @@
   if (next_source_position < length) {
     builder.AppendString(
         factory->NewSubString(string, next_source_position, length));
   }
 
   RETURN_RESULT_OR_FAILURE(isolate, builder.Finish());
 }
 
 RUNTIME_FUNCTION(Runtime_RegExpExecReThrow) {
   SealHandleScope shs(isolate);
-  DCHECK_EQ(4, args.length());
+  DCHECK_EQ(0, args.length());
   Object* exception = isolate->pending_exception();
   isolate->clear_pending_exception();
   return isolate->ReThrow(exception);
 }
 
 RUNTIME_FUNCTION(Runtime_RegExpInitializeAndCompile) {
   HandleScope scope(isolate);
   DCHECK_EQ(3, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSRegExp, regexp, 0);
   CONVERT_ARG_HANDLE_CHECKED(String, source, 1);
   CONVERT_ARG_HANDLE_CHECKED(String, flags, 2);
 
   RETURN_FAILURE_ON_EXCEPTION(isolate,
                               JSRegExp::Initialize(regexp, source, flags));
 
   return *regexp;
 }
 
 RUNTIME_FUNCTION(Runtime_IsRegExp) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_CHECKED(Object, obj, 0);
   return isolate->heap()->ToBoolean(obj->IsJSRegExp());
 }
 
 }  // namespace internal
 }  // namespace v8