[wasm] Implement stepping in wasm code

src/wasm/wasm-interpreter.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_INTERPRETER_H_
 #define V8_WASM_INTERPRETER_H_
 
 #include "src/wasm/wasm-opcodes.h"
 #include "src/zone/zone-containers.h"
 
@@ skipping 102 matching lines @@
   //                       +---------------Run()-----------+
   //                       V                               |
   // STOPPED ---Run()-->  RUNNING  ------Pause()-----+-> PAUSED  <------+
   //                       | | |                    /      |            |
   //                       | | +---- Breakpoint ---+       +-- Step() --+
   //                       | |
   //                       | +------------ Trap --------------> TRAPPED
   //                       +------------- Finish -------------> FINISHED
   enum State { STOPPED, RUNNING, PAUSED, FINISHED, TRAPPED };
 
+  // Tells a thread to pause after certain instructions.
+  enum BreakFlag : uint8_t {
+    None = 0,
+    AfterReturn = 1 << 0,
+    AfterCall = 1 << 1
+  };
+
   // Representation of a thread in the interpreter.
   class V8_EXPORT_PRIVATE Thread {
     // Don't instante Threads; they will be allocated as ThreadImpl in the
     // interpreter implementation.
     Thread() = delete;
 
    public:
     // Execution control.
     State state();
     void PushFrame(const WasmFunction* function, WasmVal* args);
@@ skipping 10 matching lines @@
     WasmVal GetReturnValue(int index = 0);
     // Returns true if the thread executed an instruction which may produce
     // nondeterministic results, e.g. float div, float sqrt, and float mul,
     // where the sign bit of a NaN is nondeterministic.
     bool PossibleNondeterminism();
 
     // Thread-specific breakpoints.
     // TODO(wasm): Implement this once we support multiple threads.
     // bool SetBreakpoint(const WasmFunction* function, int pc, bool enabled);
     // bool GetBreakpoint(const WasmFunction* function, int pc);
+
+    void AddBreakFlags(uint8_t flags);
+    void ClearBreakFlags();
   };
 
   WasmInterpreter(const ModuleBytesEnv& env, AccountingAllocator* allocator);
   ~WasmInterpreter();
 
   //==========================================================================
   // Execution controls.
   //==========================================================================
   void Run();
   void Pause();
@@ skipping 40 matching lines @@
  private:
   Zone zone_;
   WasmInterpreterInternals* internals_;
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_INTERPRETER_H_