VM: [DBC] Remove sp_ field from the DBC simulator

runtime/vm/simulator_dbc.h

 // Copyright (c) 2016, 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.
 
 #ifndef RUNTIME_VM_SIMULATOR_DBC_H_
 #define RUNTIME_VM_SIMULATOR_DBC_H_
 
 #ifndef RUNTIME_VM_SIMULATOR_H_
 #error Do not include simulator_dbc.h directly; use simulator.h.
 #endif
@@ skipping 48 matching lines @@
   // Call on program start.
   static void InitOnce();
 
   RawObject* Call(const Code& code,
                   const Array& arguments_descriptor,
                   const Array& arguments,
                   Thread* thread);
 
   void JumpToFrame(uword pc, uword sp, uword fp, Thread* thread);
 
-  uword get_sp() const { return reinterpret_cast<uword>(sp_); }
+  uword get_sp() const { return reinterpret_cast<uword>(fp_); }
   uword get_fp() const { return reinterpret_cast<uword>(fp_); }
   uword get_pc() const { return reinterpret_cast<uword>(pc_); }
 
   enum IntrinsicId {
 #define V(test_class_name, test_function_name, enum_name, type, fp)            \
   k##enum_name##Intrinsic,
     ALL_INTRINSICS_LIST(V) GRAPH_INTRINSICS_LIST(V)
 #undef V
         kIntrinsicCount,
   };
 
   static bool IsSupportedIntrinsic(IntrinsicId id) {
     return intrinsics_[id] != NULL;
   }
 
   enum SpecialIndex {
     kExceptionSpecialIndex,
     kStackTraceSpecialIndex,
     kSpecialIndexCount
   };
 
  private:
   uintptr_t* stack_;
 
   RawObject** fp_;
-  RawObject** sp_;
   uword pc_;
 
   SimulatorSetjmpBuffer* last_setjmp_buffer_;
   uword top_exit_frame_info_;
 
   RawObject* special_[kSpecialIndexCount];
 
   static IntrinsicHandler intrinsics_[kIntrinsicCount];
 
   void Exit(Thread* thread,
@@ skipping 55 matching lines @@
     last_setjmp_buffer_ = buffer;
   }
 
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_SIMULATOR_DBC_H_