[debugger] fix step-next for tail calls.

src/debug/debug.cc

 // Copyright 2012 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.
 
 #include "src/debug/debug.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 90 matching lines @@
   DCHECK(!Done());
   Next();
 }
 
 int BreakLocation::CodeIterator::GetModeMask(BreakLocatorType type) {
   int mask = 0;
   mask |= RelocInfo::ModeMask(RelocInfo::POSITION);
   mask |= RelocInfo::ModeMask(RelocInfo::STATEMENT_POSITION);
   mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_RETURN);
   mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_CALL);
+  if (isolate()->is_tail_call_elimination_enabled()) {
+    mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_TAIL_CALL);
+  }
   if (type == ALL_BREAK_LOCATIONS) {
     mask |= RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT_AT_POSITION);
     mask |= RelocInfo::ModeMask(RelocInfo::DEBUGGER_STATEMENT);
   }
   return mask;
 }
 
 void BreakLocation::CodeIterator::Next() {
   DisallowHeapAllocation no_gc;
   DCHECK(!Done());
@@ skipping 33 matching lines @@
   }
   break_index_++;
 }
 
 BreakLocation BreakLocation::CodeIterator::GetBreakLocation() {
   DebugBreakType type;
   if (RelocInfo::IsDebugBreakSlotAtReturn(rmode())) {
     type = DEBUG_BREAK_SLOT_AT_RETURN;
   } else if (RelocInfo::IsDebugBreakSlotAtCall(rmode())) {
     type = DEBUG_BREAK_SLOT_AT_CALL;
+  } else if (RelocInfo::IsDebugBreakSlotAtTailCall(rmode())) {
+    type = isolate()->is_tail_call_elimination_enabled()
+               ? DEBUG_BREAK_SLOT_AT_TAIL_CALL
+               : DEBUG_BREAK_SLOT_AT_CALL;
   } else if (RelocInfo::IsDebuggerStatement(rmode())) {
     type = DEBUGGER_STATEMENT;
   } else if (RelocInfo::IsDebugBreakSlot(rmode())) {
     type = DEBUG_BREAK_SLOT;
   } else {
     type = NOT_DEBUG_BREAK;
   }
   return BreakLocation(debug_info_, type, code_offset(), position(),
                        statement_position());
 }
@@ skipping 45 matching lines @@
 BreakLocation::DebugBreakType
 BreakLocation::BytecodeArrayIterator::GetDebugBreakType() {
   BytecodeArray* bytecode_array = debug_info_->original_bytecode_array();
   interpreter::Bytecode bytecode =
       interpreter::Bytecodes::FromByte(bytecode_array->get(code_offset()));
 
   if (bytecode == interpreter::Bytecode::kDebugger) {
     return DEBUGGER_STATEMENT;
   } else if (bytecode == interpreter::Bytecode::kReturn) {
     return DEBUG_BREAK_SLOT_AT_RETURN;
+  } else if (bytecode == interpreter::Bytecode::kTailCall) {
+    return isolate()->is_tail_call_elimination_enabled()
+               ? DEBUG_BREAK_SLOT_AT_TAIL_CALL
+               : DEBUG_BREAK_SLOT_AT_CALL;
   } else if (interpreter::Bytecodes::IsCallOrNew(bytecode)) {
     return DEBUG_BREAK_SLOT_AT_CALL;
   } else if (source_position_iterator_.is_statement()) {
     return DEBUG_BREAK_SLOT;
   } else {
     return NOT_DEBUG_BREAK;
   }
 }
 
 BreakLocation BreakLocation::BytecodeArrayIterator::GetBreakLocation() {
@@ skipping 358 matching lines @@
     OnDebugBreak(break_points_hit, false);
     return;
   }
 
   // No break point. Check for stepping.
   StepAction step_action = last_step_action();
   Address current_fp = frame->UnpaddedFP();
   Address target_fp = thread_local_.target_fp_;
   Address last_fp = thread_local_.last_fp_;
 
-  bool step_break = true;
+  bool step_break = false;
   switch (step_action) {
     case StepNone:
       return;
     case StepOut:
       // Step out has not reached the target frame yet.
       if (current_fp < target_fp) return;
+      step_break = true;
       break;
     case StepNext:
       // Step next should not break in a deeper frame.
       if (current_fp < target_fp) return;
+      // For step-next, a tail call is like a return and should break.
+      step_break = location.IsTailCall();
     // Fall through.
     case StepIn: {
       FrameSummary summary = GetFirstFrameSummary(frame);
       int offset = summary.code_offset();
-      step_break = location.IsReturn() || (current_fp != last_fp) ||
+      step_break = step_break || location.IsReturn() ||
+                   (current_fp != last_fp) ||
                    (thread_local_.last_statement_position_ !=
                     location.abstract_code()->SourceStatementPosition(offset));
       break;
     }
     case StepFrame:
       step_break = current_fp != last_fp;
       break;
   }
 
   // Clear all current stepping setup.
@@ skipping 375 matching lines @@
   // Refresh frame summary if the code has been recompiled for debugging.
   if (AbstractCode::cast(shared->code()) != *summary.abstract_code()) {
     summary = GetFirstFrameSummary(frame);
   }
 
   int call_offset =
       CallOffsetFromCodeOffset(summary.code_offset(), frame->is_interpreted());
   BreakLocation location =
       BreakLocation::FromCodeOffset(debug_info, call_offset);
 
-  // At a return statement we will step out either way.
+  // Any step at a return is a step-out.
   if (location.IsReturn()) step_action = StepOut;
+  // A step-next at a tail call is a step-out.
+  if (location.IsTailCall() && step_action == StepNext) step_action = StepOut;
 
   thread_local_.last_statement_position_ =
       debug_info->abstract_code()->SourceStatementPosition(
           summary.code_offset());
   thread_local_.last_fp_ = frame->UnpaddedFP();
 
   switch (step_action) {
     case StepNone:
       UNREACHABLE();
       break;
@@ skipping 555 matching lines @@
 
   // With no debug info there are no break points, so we can't be at a return.
   if (!shared->HasDebugInfo()) return false;
 
   DCHECK(!frame->is_optimized());
   FrameSummary summary = GetFirstFrameSummary(frame);
 
   Handle<DebugInfo> debug_info(shared->GetDebugInfo());
   BreakLocation location =
       BreakLocation::FromCodeOffset(debug_info, summary.code_offset());
-  return location.IsReturn();
+  return location.IsReturn() || location.IsTailCall();
 }
 
 
 void Debug::FramesHaveBeenDropped(StackFrame::Id new_break_frame_id,
                                   LiveEdit::FrameDropMode mode) {
   if (mode != LiveEdit::CURRENTLY_SET_MODE) {
     thread_local_.frame_drop_mode_ = mode;
   }
   thread_local_.break_frame_id_ = new_break_frame_id;
 }
@@ skipping 1001 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8