src/share/vm/opto/stringopts.cpp

@@ -1574,14 +1574,20 @@
                       Deoptimization::Action_make_not_entrant);
   }
 
   Node* result;
   if (!kit.stopped()) {
-
+    Node* char_array = NULL;
+    if (sc->num_arguments() == 1 &&
+          (sc->mode(0) == StringConcat::StringMode ||
+           sc->mode(0) == StringConcat::StringNullCheckMode)) {
+      // Handle the case when there is only a single String argument.
+      // In this case, we can just pull the value from the String itself.
+      char_array = kit.load_String_value(kit.control(), sc->argument(0));
+    } else {
     // length now contains the number of characters needed for the
     // char[] so create a new AllocateArray for the char[]
-    Node* char_array = NULL;
     {
       PreserveReexecuteState preexecs(&kit);
       // The original jvms is for an allocation of either a String or
       // StringBuffer so no stack adjustment is necessary for proper
       // reexecution.  If we deoptimize in the slow path the bytecode

@@ -1621,10 +1627,11 @@
         }
         default:
           ShouldNotReachHere();
       }
     }
+    }
 
     // If we're not reusing an existing String allocation then allocate one here.
     result = sc->string_alloc();
     if (result == NULL) {
       PreserveReexecuteState preexecs(&kit);