[lldb][NFC] Remove downstream changes related to ThreadPlan migration

The initial implementation of swift async stepping involved migrating
ThreadPlans from thread to thread. With the OS plugins introduced in
[1], this is no longer needed and the associated code is dead.

To find the relevant diffs, files were compared with their
upstream counterparts, and code mentioning the following concepts was
deleted:

* "synchronizing plans",
* "detached plans",
* "setting TIDs on a thread plan",
* "activating a thread plan stack".

The storage for thread plan stacks had been substantially changed
downstream to allow for the concepts above. This patch restores the
original storage data structures.

These were the files compared:

* ThreadPlanStack{.cpp, .h}
* ThreadPlan{.cpp, .h}
* Process{.cpp, .h}

[1]: #9839

Author: felipepiovezan

lldb/include/lldb/Target/Process.h

@@ -2380,18 +2380,6 @@ bool PruneThreadPlansForTID(lldb::tid_t tid);
 /// Prune ThreadPlanStacks for all unreported threads.
 void PruneThreadPlans();
 
-  void SynchronizeThreadPlans();
-
-  /// From the detached thread plan stacks, find the first stack that explains
-  /// the stop represented by the thread and the event.
-  lldb::ThreadPlanSP FindDetachedPlanExplainingStop(Thread &thread, Event *event_ptr);
-
-  /// Helper function for FindDetachedPlanExplainingStop. Exists only to be
-  /// marked as a C++ friend of `ThreadPlan`.
-  lldb::ThreadPlanSP DoesStackExplainStopNoLock(ThreadPlanStack &stack,
-                                                Thread &thread,
-                                                Event *event_ptr);
-
   /// Find the thread plan stack associated with thread with \a tid.
   ///
   /// \param[in] tid

lldb/include/lldb/Target/ThreadPlan.h

@@ -486,26 +486,6 @@ class ThreadPlan : public std::enable_shared_from_this<ThreadPlan>,
     return m_takes_iteration_count;
   }
 
-  bool IsTID(lldb::tid_t tid) { return tid == m_tid; }
-  bool HasTID() { return m_tid != LLDB_INVALID_THREAD_ID; }
-  lldb::tid_t GetTID() { return m_tid; }
-
-  void SetTID(lldb::tid_t tid) {
-    if (m_tid != tid) {
-      m_tid = tid;
-      ClearThreadCache();
-    }
-  }
-
-  void ClearTID() {
-    m_tid = LLDB_INVALID_THREAD_ID;
-    ClearThreadCache();
-  }
-
-  friend lldb::ThreadPlanSP
-  Process::DoesStackExplainStopNoLock(ThreadPlanStack &stack, Thread &thread,
-                                      Event *event_ptr);
-
 protected:
   // Constructors and Destructors
   ThreadPlan(ThreadPlanKind kind, const char *name, Thread &thread,

lldb/include/lldb/Target/ThreadPlanStack.h

@@ -97,12 +97,6 @@ class ThreadPlanStack {
   /// generated.
   void ClearThreadCache();
 
-  bool IsTID(lldb::tid_t tid) {
-    return GetTID() == tid;
-  }
-  lldb::tid_t GetTID();
-  void SetTID(lldb::tid_t tid);
-
 private:
   lldb::ThreadPlanSP DiscardPlanNoLock();
   lldb::ThreadPlanSP GetCurrentPlanNoLock() const;
@@ -122,9 +116,6 @@ class ThreadPlanStack {
                                           // completed plan checkpoints.
   std::unordered_map<size_t, PlanStack> m_completed_plan_store;
   mutable llvm::sys::RWMutex m_stack_mutex;
-
-  // ThreadPlanStacks shouldn't be copied.
-  ThreadPlanStack(ThreadPlanStack &rhs) = delete;
 };
 
 class ThreadPlanStackMap {
@@ -139,35 +130,16 @@ class ThreadPlanStackMap {
   void AddThread(Thread &thread) {
     std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
     lldb::tid_t tid = thread.GetID();
-    // If we already have a ThreadPlanStack for this thread, use it.
-    if (m_plans_list.find(tid) != m_plans_list.end())
-      return;
-
-    m_plans_up_container.emplace_back(
-        std::make_unique<ThreadPlanStack>(thread));
-    m_plans_list.emplace(tid, m_plans_up_container.back().get());
+    m_plans_list.emplace(tid, thread);
   }
 
   bool RemoveTID(lldb::tid_t tid) {
     std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
     auto result = m_plans_list.find(tid);
     if (result == m_plans_list.end())
       return false;
-    ThreadPlanStack *removed_stack = result->second;
+    result->second.ThreadDestroyed(nullptr);
     m_plans_list.erase(result);
-    // Now find it in the stack storage:
-    auto end = m_plans_up_container.end();
-    auto iter = std::find_if(m_plans_up_container.begin(), end,
-        [&] (std::unique_ptr<ThreadPlanStack> &stack) {
-          return stack->IsTID(tid);
-        });
-    if (iter == end)
-      return false;
-
-    // Then tell the stack its thread has been destroyed:
-    removed_stack->ThreadDestroyed(nullptr);
-    // And then remove it from the container so it goes away.
-    m_plans_up_container.erase(iter);
     return true;
   }
 
@@ -177,69 +149,22 @@ class ThreadPlanStackMap {
     if (result == m_plans_list.end())
       return nullptr;
     else
-      return result->second;
+      return &result->second;
   }
 
   /// Clear the Thread* cache that each ThreadPlan contains.
   ///
   /// This is useful in situations like when a new Thread list is being
   /// generated.
   void ClearThreadCache() {
-    std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
     for (auto &plan_list : m_plans_list)
-      plan_list.second->ClearThreadCache();
-  }
-
-  // rename to Reactivate?
-  void Activate(ThreadPlanStack &stack) {
-    std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
-    // Remove this from the detached plan list:
-    auto end = m_detached_plans.end();    
-    auto iter = std::find_if(m_detached_plans.begin(), end, 
-        [&] (ThreadPlanStack *elem) {
-          return elem == &stack; });
-    if (iter != end)
-      m_detached_plans.erase(iter);
-
-    if (m_plans_list.find(stack.GetTID()) == m_plans_list.end())
-      m_plans_list.emplace(stack.GetTID(), &stack);
-    else
-      m_plans_list.at(stack.GetTID()) = &stack;
-  }
-
-  void ScanForDetachedPlanStacks() {
-    std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
-    llvm::SmallVector<lldb::tid_t, 2> invalidated_tids;
-    for (auto &pair : m_plans_list)
-      if (pair.second->GetTID() != pair.first)
-        invalidated_tids.push_back(pair.first);
-
-    for (auto tid : invalidated_tids) {
-      auto it = m_plans_list.find(tid);
-      ThreadPlanStack *stack = it->second;
-      m_plans_list.erase(it);
-      m_detached_plans.push_back(stack);
-    }
-  }
-
-  // This gets the vector of pointers to thread plans that aren't
-  // currently running on a thread.  This is generally for thread
-  // plans that represent asynchronous operations waiting to be
-  // scheduled.
-  // The vector will never have null ThreadPlanStacks in it.
-  lldb::ThreadPlanSP FindThreadPlanInStack(
-      llvm::function_ref<lldb::ThreadPlanSP(ThreadPlanStack &)> fn) {
-    std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
-    for (auto *stack : m_detached_plans)
-      if (auto plan = fn(*stack))
-        return plan;
-    return {};
+      plan_list.second.ClearThreadCache();
   }
 
   void Clear() {
     std::lock_guard<std::recursive_mutex> guard(m_stack_map_mutex);
     for (auto &plan : m_plans_list)
-      plan.second->ThreadDestroyed(nullptr);
+      plan.second.ThreadDestroyed(nullptr);
     m_plans_list.clear();
   }
 
@@ -256,23 +181,8 @@ class ThreadPlanStackMap {
 
 private:
   Process &m_process;
-  // We don't want to make copies of these ThreadPlanStacks, there needs to be
-  // just one of these tracking each piece of work.  But we need to move the
-  // work from "attached to a TID" state to "detached" state, which is most
-  // conveniently done by having organizing containers for each of the two 
-  // states.
-  // To make it easy to move these non-copyable entities in and out of the
-  // organizing containers, we make the ThreadPlanStacks into unique_ptr's in a 
-  // storage container - m_plans_up_container.  Storing unique_ptrs means we
-  // can then use the pointer to the ThreadPlanStack in the "organizing"
-  // containers, the TID->Stack map m_plans_list, and the detached plans
-  // vector m_detached_plans.
-  
-  using PlansStore = std::vector<std::unique_ptr<ThreadPlanStack>>;
-  PlansStore m_plans_up_container;
-  std::vector<ThreadPlanStack *> m_detached_plans;
   mutable std::recursive_mutex m_stack_map_mutex;
-  using PlansList = std::unordered_map<lldb::tid_t, ThreadPlanStack *>;
+  using PlansList = std::unordered_map<lldb::tid_t, ThreadPlanStack>;
   PlansList m_plans_list;
 
 };

lldb/source/Target/Process.cpp

@@ -1373,34 +1373,6 @@ void Process::UpdateThreadListIfNeeded() {
   }
 }
 
-void Process::SynchronizeThreadPlans() {
-  m_thread_plans.ScanForDetachedPlanStacks();
-}
-
-ThreadPlanSP Process::FindDetachedPlanExplainingStop(Thread &thread,
-                                                     Event *event_ptr) {
-  return m_thread_plans.FindThreadPlanInStack(
-      [&](ThreadPlanStack &stack) -> ThreadPlanSP {
-        return DoesStackExplainStopNoLock(stack, thread, event_ptr);
-      });
-}
-
-// This extracted function only exists so that it can be marked a friend of
-// `ThreadPlan`, which is needed to call `DoPlanExplainsStop`.
-ThreadPlanSP Process::DoesStackExplainStopNoLock(ThreadPlanStack &stack,
-                                                 Thread &thread,
-                                                 Event *event_ptr) {
-  ThreadPlanSP plan_sp = stack.GetCurrentPlan();
-  plan_sp->SetTID(thread.GetID());
-  if (plan_sp->DoPlanExplainsStop(event_ptr)) {
-    stack.SetTID(thread.GetID());
-    m_thread_plans.Activate(stack);
-    return plan_sp;
-  }
-  plan_sp->ClearTID();
-  return {};
-}
-
 ThreadPlanStack *Process::FindThreadPlans(lldb::tid_t tid) {
   return m_thread_plans.Find(tid);
 }
@@ -3850,10 +3822,8 @@ bool Process::ShouldBroadcastEvent(Event *event_ptr) {
       // restarted... Asking the thread list is also not likely to go well,
       // since we are running again. So in that case just report the event.
 
-      if (!was_restarted) {
+      if (!was_restarted)
         should_resume = !m_thread_list.ShouldStop(event_ptr);
-        SynchronizeThreadPlans();
-      }
 
       if (was_restarted || should_resume || m_resume_requested) {
         Vote report_stop_vote = m_thread_list.ShouldReportStop(event_ptr);

lldb/source/Target/Thread.cpp

@@ -765,6 +765,7 @@ void Thread::DidResume() {
 void Thread::DidStop() { SetState(eStateStopped); }
 
 bool Thread::ShouldStop(Event *event_ptr) {
+  ThreadPlan *current_plan = GetCurrentPlan();
   bool should_stop = true;
 
   Log *log = GetLog(LLDBLog::Step);
@@ -818,6 +819,9 @@ bool Thread::ShouldStop(Event *event_ptr) {
     LLDB_LOGF(log, "Plan stack initial state:\n%s", s.GetData());
   }
 
+  // The top most plan always gets to do the trace log...
+  current_plan->DoTraceLog();
+
   // First query the stop info's ShouldStopSynchronous.  This handles
   // "synchronous" stop reasons, for example the breakpoint command on internal
   // breakpoints.  If a synchronous stop reason says we should not stop, then
@@ -830,16 +834,6 @@ bool Thread::ShouldStop(Event *event_ptr) {
     return false;
   }
 
-  // Call this after ShouldStopSynchronous.
-  ThreadPlan *current_plan;
-  if (auto plan = GetProcess()->FindDetachedPlanExplainingStop(*this, event_ptr))
-    current_plan = plan.get();
-  else
-    current_plan = GetCurrentPlan();
-
-  // The top most plan always gets to do the trace log…
-  current_plan->DoTraceLog();
-
   // If we've already been restarted, don't query the plans since the state
   // they would examine is not current.
   if (Process::ProcessEventData::GetRestartedFromEvent(event_ptr))
@@ -856,7 +850,6 @@ bool Thread::ShouldStop(Event *event_ptr) {
   // decide whether they still need to do more work.
 
   bool done_processing_current_plan = false;
-
   if (!current_plan->PlanExplainsStop(event_ptr)) {
     if (current_plan->TracerExplainsStop()) {
       done_processing_current_plan = true;

lldb/source/Target/ThreadPlanStack.cpp

@@ -409,13 +409,6 @@ void ThreadPlanStack::WillResume() {
   m_discarded_plans.clear();
 }
 
-lldb::tid_t ThreadPlanStack::GetTID() { return GetCurrentPlan()->GetTID(); }
-
-void ThreadPlanStack::SetTID(lldb::tid_t tid) {
-  for (auto plan_sp : m_plans)
-    plan_sp->SetTID(tid);
-}
-
 void ThreadPlanStackMap::Update(ThreadList &current_threads,
                                 bool delete_missing,
                                 bool check_for_new) {
@@ -469,8 +462,8 @@ void ThreadPlanStackMap::DumpPlans(Stream &strm,
       index_id = thread_sp->GetIndexID();
 
     if (condense_if_trivial) {
-      if (!elem.second->AnyPlans() && !elem.second->AnyCompletedPlans() &&
-          !elem.second->AnyDiscardedPlans()) {
+      if (!elem.second.AnyPlans() && !elem.second.AnyCompletedPlans() &&
+          !elem.second.AnyDiscardedPlans()) {
         strm.Printf("thread #%u: tid = 0x%4.4" PRIx64 "\n", index_id, tid);
         strm.IndentMore();
         strm.Indent();
@@ -483,7 +476,7 @@ void ThreadPlanStackMap::DumpPlans(Stream &strm,
     strm.Indent();
     strm.Printf("thread #%u: tid = 0x%4.4" PRIx64 ":\n", index_id, tid);
 
-    elem.second->DumpThreadPlans(strm, desc_level, internal);
+    elem.second.DumpThreadPlans(strm, desc_level, internal);
   }
 }