Implement Dart VM option '--trace_sim_after' in 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 75 matching lines @@
     kExceptionSpecialIndex,
     kStackTraceSpecialIndex,
     kSpecialIndexCount
   };
 
  private:
   uintptr_t* stack_;
 
   RawObject** fp_;
   uword pc_;
+  uint64_t icount_;

[zra, 2017/06/30 18:59:14]

We don't need this field in a PRODUCT build. You can exclude it with:

NOT_IN_PRODUCT(uint64_t icount_);

[alexmarkov, 2017/06/30 23:02:00]

Done.

 
   SimulatorSetjmpBuffer* last_setjmp_buffer_;
   uword top_exit_frame_info_;
 
   RawObject* special_[kSpecialIndexCount];
 
   static IntrinsicHandler intrinsics_[kIntrinsicCount];
 
   void Exit(Thread* thread,
             RawObject** base,
@@ skipping 48 matching lines @@
                      RawICData* icdata,
                      RawObject** call_base,
                      RawObject** call_top,
                      RawArray** argdesc,
                      RawObjectPool** pp,
                      uint32_t** pc,
                      RawObject*** FP,
                      RawObject*** SP,
                      bool optimized);
 
+  // Returns true if tracing of executed instructions is enabled.
+  bool IsTracingExecution() const;

[zra, 2017/06/30 18:59:14]

ditto

[alexmarkov, 2017/06/30 23:01:59]

Done.

+
+  // Prints bytecode instruction at given pc for instruction tracing.
+  void TraceInstruction(uint32_t* pc) const;

[zra, 2017/06/30 18:59:14]

ditto

[alexmarkov, 2017/06/30 23:01:59]

Done.

+
   // Longjmp support for exceptions.
   SimulatorSetjmpBuffer* last_setjmp_buffer() { return last_setjmp_buffer_; }
   void set_last_setjmp_buffer(SimulatorSetjmpBuffer* buffer) {
     last_setjmp_buffer_ = buffer;
   }
 
   friend class SimulatorSetjmpBuffer;
   DISALLOW_COPY_AND_ASSIGN(Simulator);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_SIMULATOR_DBC_H_