Simplify some of the startup code for SubStringStub::Generate.

src/arm/simulator-arm.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 1408 matching lines @@
           uint32_t uresult = static_cast<uint32_t>(result);
           uresult >>= (shift_amount - 1);
           *carry_out = (uresult & 1) == 1;
           uresult >>= 1;
           result = static_cast<int32_t>(uresult);
         }
         break;
       }
 
       case ROR: {
-        UNIMPLEMENTED();
+        if (shift_amount == 0) {
+          *carry_out = c_flag_;
+        } else {
+          uint32_t left = static_cast<uint32_t>(result) >> shift_amount;
+          uint32_t right = static_cast<uint32_t>(result) << (32 - shift_amount);
+          result = right | left;
+          *carry_out = (static_cast<uint32_t>(result) >> 31) != 0;
+        }
         break;
       }
 
       default: {
         UNREACHABLE();
         break;
       }
     }
   } else {
     // by register
@@ skipping 1975 matching lines @@
   uintptr_t address = *stack_slot;
   set_register(sp, current_sp + sizeof(uintptr_t));
   return address;
 }
 
 } }  // namespace v8::internal
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_ARM