No longer OOM on invalid string length.

src/hydrogen-instructions.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 3905 matching lines @@
                               HValue* context,
                               HValue* left,
                               HValue* right,
                               PretenureFlag pretenure_flag,
                               StringAddFlags flags,
                               Handle<AllocationSite> allocation_site) {
   if (FLAG_fold_constants && left->IsConstant() && right->IsConstant()) {
     HConstant* c_right = HConstant::cast(right);
     HConstant* c_left = HConstant::cast(left);
     if (c_left->HasStringValue() && c_right->HasStringValue()) {
-      Handle<String> concat = zone->isolate()->factory()->NewFlatConcatString(
-          c_left->StringValue(), c_right->StringValue());
-      return HConstant::New(zone, context, concat);
+      Handle<String> left_string = c_left->StringValue();
+      Handle<String> right_string = c_right->StringValue();
+      // Prevent possible exception by invalid string length.
+      if (left_string->length() + right_string->length() < String::kMaxLength) {
+        Handle<String> concat = zone->isolate()->factory()->NewFlatConcatString(
+            c_left->StringValue(), c_right->StringValue());
+        ASSERT(!concat.is_null());
+        return HConstant::New(zone, context, concat);
+      }
     }
   }
   return new(zone) HStringAdd(
       context, left, right, pretenure_flag, flags, allocation_site);
 }
 
 
 void HStringAdd::PrintDataTo(StringStream* stream) {
   if ((flags() & STRING_ADD_CHECK_BOTH) == STRING_ADD_CHECK_BOTH) {
     stream->Add("_CheckBoth");
@@ skipping 648 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal