[lldb] Extend frame recognizers to hide frames from backtraces (#104523)

Compilers and language runtimes often use helper functions that are
fundamentally uninteresting when debugging anything but the
compiler/runtime itself. This patch introduces a user-extensible
mechanism that allows for these frames to be hidden from backtraces and
automatically skipped over when navigating the stack with `up` and
`down`.

This does not affect the numbering of frames, so `f <N>` will still
provide access to the hidden frames. The `bt` output will also print a
hint that frames have been hidden.

My primary motivation for this feature is to hide thunks in the Swift
programming language, but I'm including an example recognizer for
`std::function::operator()` that I wished for myself many times while
debugging LLDB.

rdar://126629381


Example output. (Yes, my proof-of-concept recognizer could hide even
more frames if we had a method that returned the function name without
the return type or I used something that isn't based off regex, but it's
really only meant as an example).

before:
```
(lldb) thread backtrace --filtered=false
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x0000000100001f04 a.out`foo(x=1, y=1) at main.cpp:4:10
    frame #1: 0x0000000100003a00 a.out`decltype(std::declval<int (*&)(int, int)>()(std::declval<int>(), std::declval<int>())) std::__1::__invoke[abi:se200000]<int (*&)(int, int), int, int>(__f=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:149:25
    frame #2: 0x000000010000399c a.out`int std::__1::__invoke_void_return_wrapper<int, false>::__call[abi:se200000]<int (*&)(int, int), int, int>(__args=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:216:12
    frame #3: 0x0000000100003968 a.out`std::__1::__function::__alloc_func<int (*)(int, int), std::__1::allocator<int (*)(int, int)>, int (int, int)>::operator()[abi:se200000](this=0x000000016fdff280, __arg=0x000000016fdff224, __arg=0x000000016fdff220) at function.h:171:12
    frame #4: 0x00000001000026bc a.out`std::__1::__function::__func<int (*)(int, int), std::__1::allocator<int (*)(int, int)>, int (int, int)>::operator()(this=0x000000016fdff278, __arg=0x000000016fdff224, __arg=0x000000016fdff220) at function.h:313:10
    frame #5: 0x0000000100003c38 a.out`std::__1::__function::__value_func<int (int, int)>::operator()[abi:se200000](this=0x000000016fdff278, __args=0x000000016fdff224, __args=0x000000016fdff220) const at function.h:430:12
    frame #6: 0x0000000100002038 a.out`std::__1::function<int (int, int)>::operator()(this= Function = foo(int, int) , __arg=1, __arg=1) const at function.h:989:10
    frame #7: 0x0000000100001f64 a.out`main(argc=1, argv=0x000000016fdff4f8) at main.cpp:9:10
    frame #8: 0x0000000183cdf154 dyld`start + 2476
(lldb) 
```

after

```
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x0000000100001f04 a.out`foo(x=1, y=1) at main.cpp:4:10
    frame #1: 0x0000000100003a00 a.out`decltype(std::declval<int (*&)(int, int)>()(std::declval<int>(), std::declval<int>())) std::__1::__invoke[abi:se200000]<int (*&)(int, int), int, int>(__f=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:149:25
    frame #2: 0x000000010000399c a.out`int std::__1::__invoke_void_return_wrapper<int, false>::__call[abi:se200000]<int (*&)(int, int), int, int>(__args=0x000000016fdff280, __args=0x000000016fdff224, __args=0x000000016fdff220) at invoke.h:216:12
    frame #6: 0x0000000100002038 a.out`std::__1::function<int (int, int)>::operator()(this= Function = foo(int, int) , __arg=1, __arg=1) const at function.h:989:10
    frame #7: 0x0000000100001f64 a.out`main(argc=1, argv=0x000000016fdff4f8) at main.cpp:9:10
    frame #8: 0x0000000183cdf154 dyld`start + 2476
Note: Some frames were hidden by frame recognizers
```

19 files changed, 204 insertions, 41 deletions

diff --git a/lldb/source/API/SBFrame.cpp b/lldb/source/API/SBFrame.cpp
index 47fc886..2689ecb 100644
--- a/lldb/source/API/SBFrame.cpp
+++ b/lldb/source/API/SBFrame.cpp
@@ -1195,13 +1195,24 @@ bool SBFrame::IsArtificial() const {
   std::unique_lock<std::recursive_mutex> lock;
   ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
 
-  StackFrame *frame = exe_ctx.GetFramePtr();
-  if (frame)
+  if (StackFrame *frame = exe_ctx.GetFramePtr())
     return frame->IsArtificial();
 
   return false;
 }
 
+bool SBFrame::IsHidden() const {
+  LLDB_INSTRUMENT_VA(this);
+
+  std::unique_lock<std::recursive_mutex> lock;
+  ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
+
+  if (StackFrame *frame = exe_ctx.GetFramePtr())
+    return frame->IsHidden();
+
+  return false;
+}
+
 const char *SBFrame::GetFunctionName() {
   LLDB_INSTRUMENT_VA(this);
 
diff --git a/lldb/source/API/SBThread.cpp b/lldb/source/API/SBThread.cpp
index 786f62b..140a292 100644
--- a/lldb/source/API/SBThread.cpp
+++ b/lldb/source/API/SBThread.cpp
@@ -1208,7 +1208,8 @@ bool SBThread::GetStatus(SBStream &status) const {
   ExecutionContext exe_ctx(m_opaque_sp.get(), lock);
 
   if (exe_ctx.HasThreadScope()) {
-    exe_ctx.GetThreadPtr()->GetStatus(strm, 0, 1, 1, true);
+    exe_ctx.GetThreadPtr()->GetStatus(strm, 0, 1, 1, true,
+                                      /*show_hidden=*/true);
   } else
     strm.PutCString("No status");
 
diff --git a/lldb/source/Commands/CommandCompletions.cpp b/lldb/source/Commands/CommandCompletions.cpp
index 54f4b36..216aaf9 100644
--- a/lldb/source/Commands/CommandCompletions.cpp
+++ b/lldb/source/Commands/CommandCompletions.cpp
@@ -791,7 +791,7 @@ void CommandCompletions::ThreadIndexes(CommandInterpreter &interpreter,
   lldb::ThreadSP thread_sp;
   for (uint32_t idx = 0; (thread_sp = threads.GetThreadAtIndex(idx)); ++idx) {
     StreamString strm;
-    thread_sp->GetStatus(strm, 0, 1, 1, true);
+    thread_sp->GetStatus(strm, 0, 1, 1, true, /*show_hidden*/ true);
     request.TryCompleteCurrentArg(std::to_string(thread_sp->GetIndexID()),
                                   strm.GetString());
   }
@@ -835,7 +835,7 @@ void CommandCompletions::ThreadIDs(CommandInterpreter &interpreter,
   lldb::ThreadSP thread_sp;
   for (uint32_t idx = 0; (thread_sp = threads.GetThreadAtIndex(idx)); ++idx) {
     StreamString strm;
-    thread_sp->GetStatus(strm, 0, 1, 1, true);
+    thread_sp->GetStatus(strm, 0, 1, 1, true, /*show_hidden*/ true);
     request.TryCompleteCurrentArg(std::to_string(thread_sp->GetID()),
                                   strm.GetString());
   }
diff --git a/lldb/source/Commands/CommandObjectFrame.cpp b/lldb/source/Commands/CommandObjectFrame.cpp
index 29e460f..46c75e3 100644
--- a/lldb/source/Commands/CommandObjectFrame.cpp
+++ b/lldb/source/Commands/CommandObjectFrame.cpp
@@ -278,6 +278,30 @@ protected:
       if (frame_idx == UINT32_MAX)
         frame_idx = 0;
 
+      // If moving up/down by one, skip over hidden frames.
+      if (*m_options.relative_frame_offset == 1 ||
+          *m_options.relative_frame_offset == -1) {
+        uint32_t candidate_idx = frame_idx;
+        const unsigned max_depth = 12;
+        for (unsigned num_try = 0; num_try < max_depth; ++num_try) {
+          if (candidate_idx == 0 && *m_options.relative_frame_offset == -1) {
+            candidate_idx = UINT32_MAX;
+            break;
+          }
+          candidate_idx += *m_options.relative_frame_offset;
+          if (auto candidate_sp = thread->GetStackFrameAtIndex(candidate_idx)) {
+            if (candidate_sp->IsHidden())
+              continue;
+            // Now candidate_idx is the first non-hidden frame.
+            break;
+          }
+          candidate_idx = UINT32_MAX;
+          break;
+        };
+        if (candidate_idx != UINT32_MAX)
+          m_options.relative_frame_offset = candidate_idx - frame_idx;
+      }
+
       if (*m_options.relative_frame_offset < 0) {
         if (static_cast<int32_t>(frame_idx) >=
             -*m_options.relative_frame_offset)
diff --git a/lldb/source/Commands/CommandObjectMemory.cpp b/lldb/source/Commands/CommandObjectMemory.cpp
index 137b1ad..baf5d91 100644
--- a/lldb/source/Commands/CommandObjectMemory.cpp
+++ b/lldb/source/Commands/CommandObjectMemory.cpp
@@ -1570,7 +1570,8 @@ protected:
 
     const bool stop_format = false;
     for (auto thread : thread_list) {
-      thread->GetStatus(*output_stream, 0, UINT32_MAX, 0, stop_format);
+      thread->GetStatus(*output_stream, 0, UINT32_MAX, 0, stop_format,
+                        /*should_filter*/ false);
     }
 
     result.SetStatus(eReturnStatusSuccessFinishResult);
diff --git a/lldb/source/Commands/CommandObjectThread.cpp b/lldb/source/Commands/CommandObjectThread.cpp
index 605f872..6a89c16 100644
--- a/lldb/source/Commands/CommandObjectThread.cpp
+++ b/lldb/source/Commands/CommandObjectThread.cpp
@@ -89,6 +89,9 @@ public:
               "invalid boolean value for option '%c': %s", short_option,
               option_arg.data());
       } break;
+      case 'u':
+        m_filtered_backtrace = false;
+        break;
       default:
         llvm_unreachable("Unimplemented option");
       }
@@ -99,6 +102,7 @@ public:
       m_count = UINT32_MAX;
       m_start = 0;
       m_extended_backtrace = false;
+      m_filtered_backtrace = true;
     }
 
     llvm::ArrayRef<OptionDefinition> GetDefinitions() override {
@@ -109,6 +113,7 @@ public:
     uint32_t m_count;
     uint32_t m_start;
     bool m_extended_backtrace;
+    bool m_filtered_backtrace;
   };
 
   CommandObjectThreadBacktrace(CommandInterpreter &interpreter)
@@ -121,7 +126,10 @@ public:
             "call stacks.\n"
             "Use 'settings set frame-format' to customize the printing of "
             "frames in the backtrace and 'settings set thread-format' to "
-            "customize the thread header.",
+            "customize the thread header.\n"
+            "Customizable frame recognizers may filter out less interesting "
+            "frames, which results in gaps in the numbering. "
+            "Use '-u' to see all frames.",
             nullptr,
             eCommandRequiresProcess | eCommandRequiresThread |
                 eCommandTryTargetAPILock | eCommandProcessMustBeLaunched |
@@ -199,7 +207,8 @@ protected:
           strm.PutChar('\n');
           if (ext_thread_sp->GetStatus(strm, m_options.m_start,
                                        m_options.m_count,
-                                       num_frames_with_source, stop_format)) {
+                                       num_frames_with_source, stop_format,
+                                       !m_options.m_filtered_backtrace)) {
             DoExtendedBacktrace(ext_thread_sp.get(), result);
           }
         }
@@ -228,7 +237,8 @@ protected:
     const uint32_t num_frames_with_source = 0;
     const bool stop_format = true;
     if (!thread->GetStatus(strm, m_options.m_start, m_options.m_count,
-                           num_frames_with_source, stop_format, only_stacks)) {
+                           num_frames_with_source, stop_format,
+                           !m_options.m_filtered_backtrace, only_stacks)) {
       result.AppendErrorWithFormat(
           "error displaying backtrace for thread: \"0x%4.4x\"\n",
           thread->GetIndexID());
@@ -1392,7 +1402,8 @@ public:
       const uint32_t num_frames_with_source = 0;
       const bool stop_format = false;
       exception_thread_sp->GetStatus(strm, 0, UINT32_MAX,
-                                     num_frames_with_source, stop_format);
+                                     num_frames_with_source, stop_format,
+                                     /*filtered*/ false);
     }
 
     return true;
diff --git a/lldb/source/Commands/Options.td b/lldb/source/Commands/Options.td
index f050cd2..9c4dbed 100644
--- a/lldb/source/Commands/Options.td
+++ b/lldb/source/Commands/Options.td
@@ -1048,6 +1048,8 @@ let Command = "thread backtrace" in {
   Arg<"FrameIndex">, Desc<"Frame in which to start the backtrace">;
   def thread_backtrace_extended : Option<"extended", "e">, Group<1>,
   Arg<"Boolean">, Desc<"Show the extended backtrace, if available">;
+  def thread_backtrace_unfiltered : Option<"unfiltered", "u">, Group<1>,
+  Desc<"Filter out frames according to installed frame recognizers">;
 }
 
 let Command = "thread step scope" in {
diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
index 309e01e..67f01707a 100644
--- a/lldb/source/Core/Debugger.cpp
+++ b/lldb/source/Core/Debugger.cpp
@@ -1869,7 +1869,8 @@ void Debugger::HandleThreadEvent(const EventSP &event_sp) {
     ThreadSP thread_sp(
         Thread::ThreadEventData::GetThreadFromEvent(event_sp.get()));
     if (thread_sp) {
-      thread_sp->GetStatus(*GetAsyncOutputStream(), 0, 1, 1, stop_format);
+      thread_sp->GetStatus(*GetAsyncOutputStream(), 0, 1, 1, stop_format,
+                           /*show_hidden*/ true);
     }
   }
 }
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
index e451125..8729880 100644
--- a/lldb/source/Interpreter/CommandInterpreter.cpp
+++ b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -835,11 +835,12 @@ void CommandInterpreter::LoadCommandDictionary() {
   std::unique_ptr<CommandObjectRegexCommand> bt_regex_cmd_up(
       new CommandObjectRegexCommand(
           *this, "_regexp-bt",
-          "Show backtrace of the current thread's call stack.  Any numeric "
-          "argument displays at most that many frames.  The argument 'all' "
-          "displays all threads.  Use 'settings set frame-format' to customize "
+          "Show backtrace of the current thread's call stack. Any numeric "
+          "argument displays at most that many frames. The argument 'all' "
+          "displays all threads. Use 'settings set frame-format' to customize "
           "the printing of individual frames and 'settings set thread-format' "
-          "to customize the thread header.",
+          "to customize the thread header. Frame recognizers may filter the"
+          "list. Use 'thread backtrace -u (--unfiltered)' to see them all.",
           "bt [<digit> | all]", 0, false));
   if (bt_regex_cmd_up) {
     // accept but don't document "bt -c <number>" -- before bt was a regex
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
index c7202a4..c60200a 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/CPPLanguageRuntime.cpp
@@ -26,6 +26,7 @@
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/SectionLoadList.h"
 #include "lldb/Target/StackFrame.h"
+#include "lldb/Target/StackFrameRecognizer.h"
 #include "lldb/Target/ThreadPlanRunToAddress.h"
 #include "lldb/Target/ThreadPlanStepInRange.h"
 #include "lldb/Utility/Timer.h"
@@ -40,8 +41,49 @@ static ConstString g_coro_frame = ConstString("__coro_frame");
 
 char CPPLanguageRuntime::ID = 0;
 
+/// A frame recognizer that is installed to hide libc++ implementation
+/// details from the backtrace.
+class LibCXXFrameRecognizer : public StackFrameRecognizer {
+  RegularExpression m_hidden_function_regex;
+  RecognizedStackFrameSP m_hidden_frame;
+
+  struct LibCXXHiddenFrame : public RecognizedStackFrame {
+    bool ShouldHide() override { return true; }
+  };
+
+public:
+  LibCXXFrameRecognizer()
+      : m_hidden_function_regex(
+            R"(^std::__1::(__function.*::operator\(\)|__invoke))"
+            R"((\[.*\])?)"    // ABI tag.
+            R"(( const)?$)"), // const.
+        m_hidden_frame(new LibCXXHiddenFrame()) {}
+
+  std::string GetName() override { return "libc++ frame recognizer"; }
+
+  lldb::RecognizedStackFrameSP
+  RecognizeFrame(lldb::StackFrameSP frame_sp) override {
+    if (!frame_sp)
+      return {};
+    const auto &sc = frame_sp->GetSymbolContext(lldb::eSymbolContextFunction);
+    if (!sc.function)
+      return {};
+
+    if (m_hidden_function_regex.Execute(sc.function->GetNameNoArguments()))
+      return m_hidden_frame;
+
+    return {};
+  }
+};
+
 CPPLanguageRuntime::CPPLanguageRuntime(Process *process)
-    : LanguageRuntime(process) {}
+    : LanguageRuntime(process) {
+  if (process)
+    process->GetTarget().GetFrameRecognizerManager().AddRecognizer(
+        StackFrameRecognizerSP(new LibCXXFrameRecognizer()), {},
+        std::make_shared<RegularExpression>("^std::__1::"),
+        /*first_instruction_only*/ false);
+}
 
 bool CPPLanguageRuntime::IsAllowedRuntimeValue(ConstString name) {
   return name == g_this || name == g_promise || name == g_coro_frame;
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/SWIGPythonBridge.h b/lldb/source/Plugins/ScriptInterpreter/Python/SWIGPythonBridge.h
index 3026b61..5351c1a 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Python/SWIGPythonBridge.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/SWIGPythonBridge.h
@@ -227,6 +227,9 @@ public:
   LLDBSwigPython_GetRecognizedArguments(PyObject *implementor,
                                         const lldb::StackFrameSP &frame_sp);
 
+  static bool LLDBSwigPython_ShouldHide(PyObject *implementor,
+                                        const lldb::StackFrameSP &frame_sp);
+
   static bool LLDBSWIGPythonRunScriptKeywordProcess(
       const char *python_function_name, const char *session_dictionary_name,
       const lldb::ProcessSP &process, std::string &output);
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
index 335c482..2a94f11 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
@@ -1524,6 +1524,35 @@ lldb::ValueObjectListSP ScriptInterpreterPythonImpl::GetRecognizedArguments(
   return ValueObjectListSP();
 }
 
+bool ScriptInterpreterPythonImpl::ShouldHide(
+    const StructuredData::ObjectSP &os_plugin_object_sp,
+    lldb::StackFrameSP frame_sp) {
+  Locker py_lock(this, Locker::AcquireLock | Locker::NoSTDIN, Locker::FreeLock);
+
+  if (!os_plugin_object_sp)
+    return false;
+
+  StructuredData::Generic *generic = os_plugin_object_sp->GetAsGeneric();
+  if (!generic)
+    return false;
+
+  PythonObject implementor(PyRefType::Borrowed,
+                           (PyObject *)generic->GetValue());
+
+  if (!implementor.IsAllocated())
+    return false;
+
+  bool result =
+      SWIGBridge::LLDBSwigPython_ShouldHide(implementor.get(), frame_sp);
+
+  // if it fails, print the error but otherwise go on
+  if (PyErr_Occurred()) {
+    PyErr_Print();
+    PyErr_Clear();
+  }
+  return result;
+}
+
 ScriptedProcessInterfaceUP
 ScriptInterpreterPythonImpl::CreateScriptedProcessInterface() {
   return std::make_unique<ScriptedProcessPythonInterface>(*this);
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
index c2024ef..85d7995 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -107,6 +107,9 @@ public:
   GetRecognizedArguments(const StructuredData::ObjectSP &implementor,
                          lldb::StackFrameSP frame_sp) override;
 
+  bool ShouldHide(const StructuredData::ObjectSP &implementor,
+                  lldb::StackFrameSP frame_sp) override;
+
   lldb::ScriptedProcessInterfaceUP CreateScriptedProcessInterface() override;
 
   lldb::ScriptedThreadInterfaceSP CreateScriptedThreadInterface() override;
diff --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 3c9247fdb..b2a0f13 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -5545,7 +5545,8 @@ Process::RunThreadPlan(ExecutionContext &exe_ctx,
       // Print a backtrace into the log so we can figure out where we are:
       StreamString s;
       s.PutCString("Thread state after unsuccessful completion: \n");
-      thread->GetStackFrameStatus(s, 0, UINT32_MAX, true, UINT32_MAX);
+      thread->GetStackFrameStatus(s, 0, UINT32_MAX, true, UINT32_MAX,
+                                  /*show_hidden*/ true);
       log->PutString(s.GetString());
     }
     // Restore the thread state if we are going to discard the plan execution.
@@ -5819,8 +5820,8 @@ size_t Process::GetThreadStatus(Stream &strm,
           continue;
       }
       thread_sp->GetStatus(strm, start_frame, num_frames,
-                           num_frames_with_source,
-                           stop_format);
+                           num_frames_with_source, stop_format,
+                           /*show_hidden*/ num_frames <= 1);
       ++num_thread_infos_dumped;
     } else {
       Log *log = GetLog(LLDBLog::Process);
diff --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
index 3a2b4d0..0ebaf55 100644
--- a/lldb/source/Target/StackFrame.cpp
+++ b/lldb/source/Target/StackFrame.cpp
@@ -1198,6 +1198,12 @@ bool StackFrame::IsArtificial() const {
   return m_stack_frame_kind == StackFrame::Kind::Artificial;
 }
 
+bool StackFrame::IsHidden() {
+  if (auto recognized_frame_sp = GetRecognizedFrame())
+    return recognized_frame_sp->ShouldHide();
+  return false;
+}
+
 SourceLanguage StackFrame::GetLanguage() {
   CompileUnit *cu = GetSymbolContext(eSymbolContextCompUnit).comp_unit;
   if (cu)
@@ -1971,12 +1977,16 @@ bool StackFrame::GetStatus(Stream &strm, bool show_frame_info, bool show_source,
 }
 
 RecognizedStackFrameSP StackFrame::GetRecognizedFrame() {
-  if (!m_recognized_frame_sp) {
-    m_recognized_frame_sp = GetThread()
-                                ->GetProcess()
-                                ->GetTarget()
-                                .GetFrameRecognizerManager()
-                                .RecognizeFrame(CalculateStackFrame());
-  }
-  return m_recognized_frame_sp;
+  auto process = GetThread()->GetProcess();
+  if (!process)
+    return {};
+  // If recognizer list has been modified, discard cache.
+  auto &manager = process->GetTarget().GetFrameRecognizerManager();
+  auto new_generation = manager.GetGeneration();
+  if (m_frame_recognizer_generation != new_generation)
+    m_recognized_frame_sp.reset();
+  m_frame_recognizer_generation = new_generation;
+  if (!m_recognized_frame_sp.has_value())
+    m_recognized_frame_sp = manager.RecognizeFrame(CalculateStackFrame());
+  return m_recognized_frame_sp.value();
 }
diff --git a/lldb/source/Target/StackFrameList.cpp b/lldb/source/Target/StackFrameList.cpp
index 0cf9ce1..7808bd3 100644
--- a/lldb/source/Target/StackFrameList.cpp
+++ b/lldb/source/Target/StackFrameList.cpp
@@ -924,7 +924,7 @@ StackFrameList::GetStackFrameSPForStackFramePtr(StackFrame *stack_frame_ptr) {
 size_t StackFrameList::GetStatus(Stream &strm, uint32_t first_frame,
                                  uint32_t num_frames, bool show_frame_info,
                                  uint32_t num_frames_with_source,
-                                 bool show_unique,
+                                 bool show_unique, bool show_hidden,
                                  const char *selected_frame_marker) {
   size_t num_frames_displayed = 0;
 
@@ -951,7 +951,6 @@ size_t StackFrameList::GetStatus(Stream &strm, uint32_t first_frame,
     unselected_marker = buffer.c_str();
   }
   const char *marker = nullptr;
-
   for (frame_idx = first_frame; frame_idx < last_frame; ++frame_idx) {
     frame_sp = GetFrameAtIndex(frame_idx);
     if (!frame_sp)
@@ -963,6 +962,11 @@ size_t StackFrameList::GetStatus(Stream &strm, uint32_t first_frame,
       else
         marker = unselected_marker;
     }
+
+    // Hide uninteresting frames unless it's the selected frame.
+    if (!show_hidden && frame_sp != selected_frame_sp && frame_sp->IsHidden())
+      continue;
+
     // Check for interruption here.  If we're fetching arguments, this loop
     // can go slowly:
     Debugger &dbg = m_thread.GetProcess()->GetTarget().GetDebugger();
diff --git a/lldb/source/Target/StackFrameRecognizer.cpp b/lldb/source/Target/StackFrameRecognizer.cpp
index 0ccb1ae..44411af 100644
--- a/lldb/source/Target/StackFrameRecognizer.cpp
+++ b/lldb/source/Target/StackFrameRecognizer.cpp
@@ -17,10 +17,14 @@ using namespace lldb;
 using namespace lldb_private;
 
 class ScriptedRecognizedStackFrame : public RecognizedStackFrame {
+  bool m_hidden;
+
 public:
-  ScriptedRecognizedStackFrame(ValueObjectListSP args) {
-    m_arguments = args;
+  ScriptedRecognizedStackFrame(ValueObjectListSP args, bool hidden)
+      : m_hidden(hidden) {
+    m_arguments = std::move(args);
   }
+  bool ShouldHide() override { return m_hidden; }
 };
 
 ScriptedStackFrameRecognizer::ScriptedStackFrameRecognizer(
@@ -38,13 +42,22 @@ ScriptedStackFrameRecognizer::RecognizeFrame(lldb::StackFrameSP frame) {
   ValueObjectListSP args =
       m_interpreter->GetRecognizedArguments(m_python_object_sp, frame);
   auto args_synthesized = ValueObjectListSP(new ValueObjectList());
-  for (const auto &o : args->GetObjects()) {
-    args_synthesized->Append(ValueObjectRecognizerSynthesizedValue::Create(
-        *o, eValueTypeVariableArgument));
+  if (args) {
+    for (const auto &o : args->GetObjects())
+      args_synthesized->Append(ValueObjectRecognizerSynthesizedValue::Create(
+          *o, eValueTypeVariableArgument));
   }
 
+  bool hidden = m_interpreter->ShouldHide(m_python_object_sp, frame);
+
   return RecognizedStackFrameSP(
-      new ScriptedRecognizedStackFrame(args_synthesized));
+      new ScriptedRecognizedStackFrame(args_synthesized, hidden));
+}
+
+void StackFrameRecognizerManager::BumpGeneration() {
+  uint32_t n = m_generation;
+  n = (n + 1) & ((1 << 16) - 1);
+  m_generation = n;
 }
 
 void StackFrameRecognizerManager::AddRecognizer(
@@ -53,6 +66,7 @@ void StackFrameRecognizerManager::AddRecognizer(
   m_recognizers.push_front({(uint32_t)m_recognizers.size(), recognizer, false,
                             module, RegularExpressionSP(), symbols,
                             RegularExpressionSP(), first_instruction_only});
+  BumpGeneration();
 }
 
 void StackFrameRecognizerManager::AddRecognizer(
@@ -61,6 +75,7 @@ void StackFrameRecognizerManager::AddRecognizer(
   m_recognizers.push_front({(uint32_t)m_recognizers.size(), recognizer, true,
                             ConstString(), module, std::vector<ConstString>(),
                             symbol, first_instruction_only});
+  BumpGeneration();
 }
 
 void StackFrameRecognizerManager::ForEach(
@@ -97,10 +112,12 @@ bool StackFrameRecognizerManager::RemoveRecognizerWithID(
   if (found == m_recognizers.end())
     return false;
   m_recognizers.erase(found);
+  BumpGeneration();
   return true;
 }
 
 void StackFrameRecognizerManager::RemoveAllRecognizers() {
+  BumpGeneration();
   m_recognizers.clear();
 }
 
diff --git a/lldb/source/Target/Thread.cpp b/lldb/source/Target/Thread.cpp
index 74d1a26..fcf0f4e 100644
--- a/lldb/source/Target/Thread.cpp
+++ b/lldb/source/Target/Thread.cpp
@@ -1748,7 +1748,7 @@ std::string Thread::RunModeAsString(lldb::RunMode mode) {
 
 size_t Thread::GetStatus(Stream &strm, uint32_t start_frame,
                          uint32_t num_frames, uint32_t num_frames_with_source,
-                         bool stop_format, bool only_stacks) {
+                         bool stop_format, bool show_hidden, bool only_stacks) {
 
   if (!only_stacks) {
     ExecutionContext exe_ctx(shared_from_this());
@@ -1795,7 +1795,7 @@ size_t Thread::GetStatus(Stream &strm, uint32_t start_frame,
 
     num_frames_shown = GetStackFrameList()->GetStatus(
         strm, start_frame, num_frames, show_frame_info, num_frames_with_source,
-        show_frame_unique, selected_frame_marker);
+        show_frame_unique, show_hidden, selected_frame_marker);
     if (num_frames == 1)
       strm.IndentLess();
     strm.IndentLess();
@@ -1893,9 +1893,11 @@ bool Thread::GetDescription(Stream &strm, lldb::DescriptionLevel level,
 
 size_t Thread::GetStackFrameStatus(Stream &strm, uint32_t first_frame,
                                    uint32_t num_frames, bool show_frame_info,
-                                   uint32_t num_frames_with_source) {
-  return GetStackFrameList()->GetStatus(
-      strm, first_frame, num_frames, show_frame_info, num_frames_with_source);
+                                   uint32_t num_frames_with_source,
+                                   bool show_hidden) {
+  return GetStackFrameList()->GetStatus(strm, first_frame, num_frames,
+                                        show_frame_info, num_frames_with_source,
+                                        /*show_unique*/ false, show_hidden);
 }
 
 Unwind &Thread::GetUnwinder() {
diff --git a/lldb/source/Target/ThreadPlanStepOut.cpp b/lldb/source/Target/ThreadPlanStepOut.cpp
index 0a1e2ae..8ca1dbc 100644
--- a/lldb/source/Target/ThreadPlanStepOut.cpp
+++ b/lldb/source/Target/ThreadPlanStepOut.cpp
@@ -58,7 +58,7 @@ ThreadPlanStepOut::ThreadPlanStepOut(
     return; // we can't do anything here.  ValidatePlan() will return false.
 
   // While stepping out, behave as-if artificial frames are not present.
-  while (return_frame_sp->IsArtificial()) {
+  while (return_frame_sp->IsArtificial() || return_frame_sp->IsHidden()) {
     m_stepped_past_frames.push_back(return_frame_sp);
 
     ++return_frame_index;