[debugger] simplify stepping logic.

Now that we do not support arbitrary step count anymore, we can
make this a lot easier.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/1539483002

Cr-Commit-Position: refs/heads/master@{#32966}

src/debug/debug-scopes.cc

@@ -63,8 +63,7 @@ ScopeIterator::ScopeIterator(Isolate* isolate, FrameInspector* frame_inspector,
     Address call_pc = GetFrame()->pc() - 1;
 
     // Find the break point where execution has stopped.
-    BreakLocation location =
-        BreakLocation::FromAddress(debug_info, ALL_BREAK_LOCATIONS, call_pc);
+    BreakLocation location = BreakLocation::FromAddress(debug_info, call_pc);
 
     ignore_nested_scopes = location.IsReturn();
   }

src/debug/debug.h

@@ -64,15 +64,12 @@ class BreakLocation {
  public:
   // Find the break point at the supplied address, or the closest one before
   // the address.
-  static BreakLocation FromAddress(Handle<DebugInfo> debug_info,
-                                   BreakLocatorType type, Address pc);
+  static BreakLocation FromAddress(Handle<DebugInfo> debug_info, Address pc);
 
-  static void FromAddressSameStatement(Handle<DebugInfo> debug_info,
-                                       BreakLocatorType type, Address pc,
+  static void FromAddressSameStatement(Handle<DebugInfo> debug_info, Address pc,
                                        List<BreakLocation>* result_out);
 
-  static BreakLocation FromPosition(Handle<DebugInfo> debug_info,
-                                    BreakLocatorType type, int position,
+  static BreakLocation FromPosition(Handle<DebugInfo> debug_info, int position,
                                     BreakPositionAlignment alignment);
 
   bool IsDebugBreak() const;
@@ -152,8 +149,7 @@ class BreakLocation {
 
   friend class Debug;
 
-  static int BreakIndexFromAddress(Handle<DebugInfo> debug_info,
-                                   BreakLocatorType type, Address pc);
+  static int BreakIndexFromAddress(Handle<DebugInfo> debug_info, Address pc);
 
   void SetDebugBreak();
   void ClearDebugBreak();
@@ -408,15 +404,12 @@ class Debug {
   bool IsBreakOnException(ExceptionBreakType type);
 
   // Stepping handling.
-  void PrepareStep(StepAction step_action, int step_count);
+  void PrepareStep(StepAction step_action);
   void PrepareStepIn(Handle<JSFunction> function);
   void PrepareStepOnThrow();
   void ClearStepping();
   void ClearStepOut();
   void EnableStepIn();
-  bool IsStepping() { return thread_local_.step_count_ > 0; }
-  bool StepNextContinue(BreakLocation* location, JavaScriptFrame* frame);
-  bool StepOutActive() { return thread_local_.step_out_fp_ != 0; }
 
   void GetStepinPositions(JavaScriptFrame* frame, StackFrame::Id frame_id,
                           List<int>* results_out);
@@ -624,15 +617,11 @@ class Debug {
     // Source statement position from last step next action.
     int last_statement_position_;
 
-    // Number of steps left to perform before debug event.
-    int step_count_;
-
     // Frame pointer from last step next or step frame action.
     Address last_fp_;
 
-    // Frame pointer for the frame where debugger should be called when current
-    // step out action is completed.
-    Address step_out_fp_;
+    // Frame pointer of the target frame we want to arrive at.
+    Address target_fp_;
 
     // Whether functions are flooded on entry for step-in and step-frame.
     // If we stepped out to the embedder, disable flooding to spill stepping

src/runtime/runtime-debug.cc

@@ -1231,7 +1231,7 @@ RUNTIME_FUNCTION(Runtime_PrepareStep) {
   isolate->debug()->ClearStepping();
 
   // Prepare step.
-  isolate->debug()->PrepareStep(static_cast<StepAction>(step_action), 1);
+  isolate->debug()->PrepareStep(static_cast<StepAction>(step_action));
   return isolate->heap()->undefined_value();
 }
 

src/runtime/runtime-observe.cc

@@ -65,16 +65,8 @@ RUNTIME_FUNCTION(Runtime_DeliverObservationChangeRecords) {
   catcher.SetVerbose(true);
   Handle<Object> argv[] = {argument};
 
-  // Allow stepping into the observer callback.
-  Debug* debug = isolate->debug();
-  if (debug->is_active() && debug->IsStepping() &&
-      debug->last_step_action() == StepIn) {
-    // Previous StepIn may have activated a StepOut if it was at the frame exit.
-    // In this case to be able to step into the callback again, we need to clear
-    // the step out first.
-    debug->ClearStepOut();
-    debug->FloodWithOneShot(callback);
-  }
+  // If we are in step-in mode, flood the handler.
+  isolate->debug()->EnableStepIn();
 
   USE(Execution::Call(isolate, callback, isolate->factory()->undefined_value(),
                       arraysize(argv), argv));

test/cctest/test-debug.cc

@@ -341,7 +341,7 @@ static void ChangeBreakOnExceptionFromJS(v8::Isolate* isolate, bool caught,
 // Prepare to step to next break location.
 static void PrepareStep(StepAction step_action) {
   v8::internal::Debug* debug = CcTest::i_isolate()->debug();
-  debug->PrepareStep(step_action, 1);
+  debug->PrepareStep(step_action);
 }