diff --git a/lldb/source/Commands/CommandObjectThread.cpp b/lldb/source/Commands/CommandObjectThread.cpp
@@ -42,10 +42,44 @@ using namespace lldb;
 using namespace lldb_private;
 
 //-------------------------------------------------------------------------
-// CommandObjectThreadBacktrace
+// CommandObjectIterateOverThreads
 //-------------------------------------------------------------------------
 
 class CommandObjectIterateOverThreads : public CommandObjectParsed {
+
+  class UniqueStack {
+
+  public:
+    UniqueStack(std::stack<lldb::addr_t> stack_frames, uint32_t thread_index_id)
+        : m_stack_frames(stack_frames) {
+      m_thread_index_ids.push_back(thread_index_id);
+    }
+
+    void AddThread(uint32_t thread_index_id) const {
+      m_thread_index_ids.push_back(thread_index_id);
+    }
+
+    const std::vector<uint32_t> &GetUniqueThreadIndexIDs() const {
+      return m_thread_index_ids;
+    }
+
+    lldb::tid_t GetRepresentativeThread() const {
+      return m_thread_index_ids.front();
+    }
+
+    friend bool inline operator<(const UniqueStack &lhs,
+                                 const UniqueStack &rhs) {
+      return lhs.m_stack_frames < rhs.m_stack_frames;
+    }
+
+  protected:
+    // Mark the thread index as mutable, as we don't care about it from a const
+    // perspective, we only care about m_stack_frames so we keep our std::set
+    // sorted.
+    mutable std::vector<uint32_t> m_thread_index_ids;
+    std::stack<lldb::addr_t> m_stack_frames;
+  };
+
 public:
   CommandObjectIterateOverThreads(CommandInterpreter &interpreter,
                                   const char *name, const char *help,
@@ -57,20 +91,23 @@ class CommandObjectIterateOverThreads : public CommandObjectParsed {
   bool DoExecute(Args &command, CommandReturnObject &result) override {
     result.SetStatus(m_success_return);
 
+    bool all_threads = false;
     if (command.GetArgumentCount() == 0) {
       Thread *thread = m_exe_ctx.GetThreadPtr();
       if (!HandleOneThread(thread->GetID(), result))
         return false;
       return result.Succeeded();
+    } else if (command.GetArgumentCount() == 1) {
+      all_threads = ::strcmp(command.GetArgumentAtIndex(0), "all") == 0;
+      m_unique_stacks = ::strcmp(command.GetArgumentAtIndex(0), "unique") == 0;
     }
 
     // Use tids instead of ThreadSPs to prevent deadlocking problems which
     // result from JIT-ing
     // code while iterating over the (locked) ThreadSP list.
     std::vector<lldb::tid_t> tids;
 
-    if (command.GetArgumentCount() == 1 &&
-        ::strcmp(command.GetArgumentAtIndex(0), "all") == 0) {
+    if (all_threads || m_unique_stacks) {
       Process *process = m_exe_ctx.GetProcessPtr();
 
       for (ThreadSP thread_sp : process->Threads())
@@ -108,15 +145,47 @@ class CommandObjectIterateOverThreads : public CommandObjectParsed {
       }
     }
 
-    uint32_t idx = 0;
-    for (const lldb::tid_t &tid : tids) {
-      if (idx != 0 && m_add_return)
-        result.AppendMessage("");
+    if (m_unique_stacks) {
+      // Iterate over threads, finding unique stack buckets.
+      std::set<UniqueStack> unique_stacks;
+      for (const lldb::tid_t &tid : tids) {
+        if (!BucketThread(tid, unique_stacks, result)) {
+          return false;
+        }
+      }
 
-      if (!HandleOneThread(tid, result))
-        return false;
+      // Write the thread id's and unique call stacks to the output stream
+      Stream &strm = result.GetOutputStream();
+      Process *process = m_exe_ctx.GetProcessPtr();
+      for (const UniqueStack &stack : unique_stacks) {
+        // List the common thread ID's
+        const std::vector<uint32_t> &thread_index_ids =
+            stack.GetUniqueThreadIndexIDs();
+        strm.Printf("%lu thread(s) ", thread_index_ids.size());
+        for (const uint32_t &thread_index_id : thread_index_ids) {
+          strm.Printf("#%u ", thread_index_id);
+        }
+        strm.EOL();
 
-      ++idx;
+        // List the shared call stack for this set of threads
+        uint32_t representative_thread_id = stack.GetRepresentativeThread();
+        ThreadSP thread = process->GetThreadList().FindThreadByIndexID(
+            representative_thread_id);
+        if (!HandleOneThread(thread->GetID(), result)) {
+          return false;
+        }
+      }
+    } else {
+      uint32_t idx = 0;
+      for (const lldb::tid_t &tid : tids) {
+        if (idx != 0 && m_add_return)
+          result.AppendMessage("");
+
+        if (!HandleOneThread(tid, result))
+          return false;
+
+        ++idx;
+      }
     }
     return result.Succeeded();
   }
@@ -134,7 +203,43 @@ class CommandObjectIterateOverThreads : public CommandObjectParsed {
 
   virtual bool HandleOneThread(lldb::tid_t, CommandReturnObject &result) = 0;
 
+  bool BucketThread(lldb::tid_t tid, std::set<UniqueStack> &unique_stacks,
+                    CommandReturnObject &result) {
+    // Grab the corresponding thread for the given thread id.
+    Process *process = m_exe_ctx.GetProcessPtr();
+    Thread *thread = process->GetThreadList().FindThreadByID(tid).get();
+    if (thread == nullptr) {
+      result.AppendErrorWithFormat("Failed to process thread# %lu.\n", tid);
+      result.SetStatus(eReturnStatusFailed);
+      return false;
+    }
+
+    // Collect the each frame's address for this call-stack
+    std::stack<lldb::addr_t> stack_frames;
+    const uint32_t frame_count = thread->GetStackFrameCount();
+    for (uint32_t frame_index = 0; frame_index < frame_count; frame_index++) {
+      const lldb::StackFrameSP frame_sp =
+          thread->GetStackFrameAtIndex(frame_index);
+      const lldb::addr_t pc = frame_sp->GetStackID().GetPC();
+      stack_frames.push(pc);
+    }
+
+    uint32_t thread_index_id = thread->GetIndexID();
+    UniqueStack new_unique_stack(stack_frames, thread_index_id);
+
+    // Try to match the threads stack to and existing entry.
+    std::set<UniqueStack>::iterator matching_stack =
+        unique_stacks.find(new_unique_stack);
+    if (matching_stack != unique_stacks.end()) {
+      matching_stack->AddThread(thread_index_id);
+    } else {
+      unique_stacks.insert(new_unique_stack);
+    }
+    return true;
+  }
+
   ReturnStatus m_success_return = eReturnStatusSuccessFinishResult;
+  bool m_unique_stacks = false;
   bool m_add_return = true;
 };
 
@@ -218,9 +323,10 @@ class CommandObjectThreadBacktrace : public CommandObjectIterateOverThreads {
       : CommandObjectIterateOverThreads(
             interpreter, "thread backtrace",
             "Show thread call stacks.  Defaults to the current thread, thread "
-            "indexes can be specified as arguments.  Use the thread-index "
-            "\"all\" "
-            "to see all threads.",
+            "indexes can be specified as arguments.\n"
+            "Use the thread-index \"all\" to see all threads.\n"
+            "Use the thread-index \"unique\" to see threads grouped by unique "
+            "call stacks.",
             nullptr,
             eCommandRequiresProcess | eCommandRequiresThread |
                 eCommandTryTargetAPILock | eCommandProcessMustBeLaunched |
@@ -270,11 +376,14 @@ class CommandObjectThreadBacktrace : public CommandObjectIterateOverThreads {
 
     Stream &strm = result.GetOutputStream();
 
+    // Only dump stack info if we processing unique stacks.
+    const bool only_stacks = m_unique_stacks;
+
     // Don't show source context when doing backtraces.
     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)) {
+                           num_frames_with_source, stop_format, only_stacks)) {
       result.AppendErrorWithFormat(
           "error displaying backtrace for thread: \"0x%4.4x\"\n",
           thread->GetIndexID());

diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
@@ -112,6 +112,12 @@ OptionEnumValueElement g_language_enumerators[] = {
   "{ "                                                                         \
   "${module.file.basename}{`${function.name-with-args}"                        \
   "{${frame.no-debug}${function.pc-offset}}}}"
+
+#define MODULE_WITH_FUNC_NO_ARGS                                               \
+  "{ "                                                                         \
+  "${module.file.basename}{`${function.name-without-args}"                     \
+  "{${frame.no-debug}${function.pc-offset}}}}"
+
 #define FILE_AND_LINE "{ at ${line.file.basename}:${line.number}}"
 #define IS_OPTIMIZED "{${function.is-optimized} [opt]}"
 
@@ -141,6 +147,10 @@ OptionEnumValueElement g_language_enumerators[] = {
   "frame #${frame.index}: ${frame.pc}" MODULE_WITH_FUNC FILE_AND_LINE          \
       IS_OPTIMIZED "\\n"
 
+#define DEFAULT_FRAME_FORMAT_NO_ARGS                                           \
+  "frame #${frame.index}: ${frame.pc}" MODULE_WITH_FUNC_NO_ARGS FILE_AND_LINE  \
+      IS_OPTIMIZED "\\n"
+
 // Three parts to this disassembly format specification:
 //   1. If this is a new function/symbol (no previous symbol/function), print
 //      dylib`funcname:\n
@@ -186,13 +196,15 @@ static PropertyDefinition g_properties[] = {
     {"auto-confirm", OptionValue::eTypeBoolean, true, false, nullptr, nullptr,
      "If true all confirmation prompts will receive their default reply."},
     {"disassembly-format", OptionValue::eTypeFormatEntity, true, 0,
-     DEFAULT_DISASSEMBLY_FORMAT, nullptr, "The default disassembly format "
-                                          "string to use when disassembling "
-                                          "instruction sequences."},
+     DEFAULT_DISASSEMBLY_FORMAT, nullptr,
+     "The default disassembly format "
+     "string to use when disassembling "
+     "instruction sequences."},
     {"frame-format", OptionValue::eTypeFormatEntity, true, 0,
-     DEFAULT_FRAME_FORMAT, nullptr, "The default frame format string to use "
-                                    "when displaying stack frame information "
-                                    "for threads."},
+     DEFAULT_FRAME_FORMAT, nullptr,
+     "The default frame format string to use "
+     "when displaying stack frame information "
+     "for threads."},
     {"notify-void", OptionValue::eTypeBoolean, true, false, nullptr, nullptr,
      "Notify the user explicitly if an expression returns void (default: "
      "false)."},
@@ -203,18 +215,21 @@ static PropertyDefinition g_properties[] = {
      nullptr, g_language_enumerators,
      "The script language to be used for evaluating user-written scripts."},
     {"stop-disassembly-count", OptionValue::eTypeSInt64, true, 4, nullptr,
-     nullptr, "The number of disassembly lines to show when displaying a "
-              "stopped context."},
+     nullptr,
+     "The number of disassembly lines to show when displaying a "
+     "stopped context."},
     {"stop-disassembly-display", OptionValue::eTypeEnum, true,
      Debugger::eStopDisassemblyTypeNoDebugInfo, nullptr,
      g_show_disassembly_enum_values,
      "Control when to display disassembly when displaying a stopped context."},
     {"stop-line-count-after", OptionValue::eTypeSInt64, true, 3, nullptr,
-     nullptr, "The number of sources lines to display that come after the "
-              "current source line when displaying a stopped context."},
+     nullptr,
+     "The number of sources lines to display that come after the "
+     "current source line when displaying a stopped context."},
     {"stop-line-count-before", OptionValue::eTypeSInt64, true, 3, nullptr,
-     nullptr, "The number of sources lines to display that come before the "
-              "current source line when displaying a stopped context."},
+     nullptr,
+     "The number of sources lines to display that come before the "
+     "current source line when displaying a stopped context."},
     {"stop-show-column", OptionValue::eTypeEnum, false,
      eStopShowColumnAnsiOrCaret, nullptr, s_stop_show_column_values,
      "If true, LLDB will use the column information from the debug info to "
@@ -232,19 +247,22 @@ static PropertyDefinition g_properties[] = {
     {"term-width", OptionValue::eTypeSInt64, true, 80, nullptr, nullptr,
      "The maximum number of columns to use for displaying text."},
     {"thread-format", OptionValue::eTypeFormatEntity, true, 0,
-     DEFAULT_THREAD_FORMAT, nullptr, "The default thread format string to use "
-                                     "when displaying thread information."},
+     DEFAULT_THREAD_FORMAT, nullptr,
+     "The default thread format string to use "
+     "when displaying thread information."},
     {"thread-stop-format", OptionValue::eTypeFormatEntity, true, 0,
-     DEFAULT_THREAD_STOP_FORMAT, nullptr, "The default thread format  "
-                                     "string to usewhen displaying thread "
-                                     "information as part of the stop display."},
+     DEFAULT_THREAD_STOP_FORMAT, nullptr,
+     "The default thread format  "
+     "string to use when displaying thread "
+     "information as part of the stop display."},
     {"use-external-editor", OptionValue::eTypeBoolean, true, false, nullptr,
      nullptr, "Whether to use an external editor or not."},
     {"use-color", OptionValue::eTypeBoolean, true, true, nullptr, nullptr,
      "Whether to use Ansi color codes or not."},
     {"auto-one-line-summaries", OptionValue::eTypeBoolean, true, true, nullptr,
-     nullptr, "If true, LLDB will automatically display small structs in "
-              "one-liner format (default: true)."},
+     nullptr,
+     "If true, LLDB will automatically display small structs in "
+     "one-liner format (default: true)."},
     {"auto-indent", OptionValue::eTypeBoolean, true, true, nullptr, nullptr,
      "If true, LLDB will auto indent/outdent code. Currently only supported in "
      "the REPL (default: true)."},
@@ -255,8 +273,13 @@ static PropertyDefinition g_properties[] = {
      "The tab size to use when indenting code in multi-line input mode "
      "(default: 4)."},
     {"escape-non-printables", OptionValue::eTypeBoolean, true, true, nullptr,
-     nullptr, "If true, LLDB will automatically escape non-printable and "
-              "escape characters when formatting strings."},
+     nullptr,
+     "If true, LLDB will automatically escape non-printable and "
+     "escape characters when formatting strings."},
+    {"frame-format-unique", OptionValue::eTypeFormatEntity, true, 0,
+     DEFAULT_FRAME_FORMAT_NO_ARGS, nullptr,
+     "The default frame format string to use when displaying stack frame"
+     "information for threads from thread backtrace unique."},
     {nullptr, OptionValue::eTypeInvalid, true, 0, nullptr, nullptr, nullptr}};
 
 enum {
@@ -282,7 +305,8 @@ enum {
   ePropertyAutoIndent,
   ePropertyPrintDecls,
   ePropertyTabSize,
-  ePropertyEscapeNonPrintables
+  ePropertyEscapeNonPrintables,
+  ePropertyFrameFormatUnique,
 };
 
 LoadPluginCallbackType Debugger::g_load_plugin_callback = nullptr;
@@ -358,6 +382,11 @@ const FormatEntity::Entry *Debugger::GetFrameFormat() const {
   return m_collection_sp->GetPropertyAtIndexAsFormatEntity(nullptr, idx);
 }
 
+const FormatEntity::Entry *Debugger::GetFrameFormatUnique() const {
+  const uint32_t idx = ePropertyFrameFormatUnique;
+  return m_collection_sp->GetPropertyAtIndexAsFormatEntity(nullptr, idx);
+}
+
 bool Debugger::GetNotifyVoid() const {
   const uint32_t idx = ePropertyNotiftVoid;
   return m_collection_sp->GetPropertyAtIndexAsBoolean(

diff --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
@@ -1744,7 +1744,7 @@ void StackFrame::CalculateExecutionContext(ExecutionContext &exe_ctx) {
   exe_ctx.SetContext(shared_from_this());
 }
 
-void StackFrame::DumpUsingSettingsFormat(Stream *strm,
+void StackFrame::DumpUsingSettingsFormat(Stream *strm, bool show_unique,
                                          const char *frame_marker) {
   if (strm == nullptr)
     return;
@@ -1758,8 +1758,13 @@ void StackFrame::DumpUsingSettingsFormat(Stream *strm,
 
   const FormatEntity::Entry *frame_format = nullptr;
   Target *target = exe_ctx.GetTargetPtr();
-  if (target)
-    frame_format = target->GetDebugger().GetFrameFormat();
+  if (target) {
+    if (show_unique) {
+      frame_format = target->GetDebugger().GetFrameFormatUnique();
+    } else {
+      frame_format = target->GetDebugger().GetFrameFormat();
+    }
+  }
   if (frame_format && FormatEntity::Format(*frame_format, s, &m_sc, &exe_ctx,
                                            nullptr, nullptr, false, false)) {
     strm->PutCString(s.GetString());
@@ -1841,11 +1846,10 @@ bool StackFrame::HasCachedData() const {
 }
 
 bool StackFrame::GetStatus(Stream &strm, bool show_frame_info, bool show_source,
-                           const char *frame_marker) {
-
+                           bool show_unique, const char *frame_marker) {
   if (show_frame_info) {
     strm.Indent();
-    DumpUsingSettingsFormat(&strm, frame_marker);
+    DumpUsingSettingsFormat(&strm, show_unique, frame_marker);
   }
 
   if (show_source) {

diff --git a/lldb/source/Target/StackFrameList.cpp b/lldb/source/Target/StackFrameList.cpp
@@ -802,6 +802,7 @@ 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,
                                  const char *selected_frame_marker) {
   size_t num_frames_displayed = 0;
 
@@ -842,7 +843,7 @@ size_t StackFrameList::GetStatus(Stream &strm, uint32_t first_frame,
 
     if (!frame_sp->GetStatus(strm, show_frame_info,
                              num_frames_with_source > (first_frame - frame_idx),
-                             marker))
+                             show_unique, marker))
       break;
     ++num_frames_displayed;
   }

diff --git a/lldb/source/Target/Thread.cpp b/lldb/source/Target/Thread.cpp
@@ -1913,47 +1913,50 @@ const char *Thread::RunModeAsCString(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) {
-  ExecutionContext exe_ctx(shared_from_this());
-  Target *target = exe_ctx.GetTargetPtr();
-  Process *process = exe_ctx.GetProcessPtr();
-  size_t num_frames_shown = 0;
-  strm.Indent();
-  bool is_selected = false;
-  if (process) {
-    if (process->GetThreadList().GetSelectedThread().get() == this)
-      is_selected = true;
-  }
-  strm.Printf("%c ", is_selected ? '*' : ' ');
-  if (target && target->GetDebugger().GetUseExternalEditor()) {
-    StackFrameSP frame_sp = GetStackFrameAtIndex(start_frame);
-    if (frame_sp) {
-      SymbolContext frame_sc(
-          frame_sp->GetSymbolContext(eSymbolContextLineEntry));
-      if (frame_sc.line_entry.line != 0 && frame_sc.line_entry.file) {
-        Host::OpenFileInExternalEditor(frame_sc.line_entry.file,
-                                       frame_sc.line_entry.line);
+                         bool stop_format, bool only_stacks) {
+
+  if (!only_stacks) {
+    ExecutionContext exe_ctx(shared_from_this());
+    Target *target = exe_ctx.GetTargetPtr();
+    Process *process = exe_ctx.GetProcessPtr();
+    strm.Indent();
+    bool is_selected = false;
+    if (process) {
+      if (process->GetThreadList().GetSelectedThread().get() == this)
+        is_selected = true;
+    }
+    strm.Printf("%c ", is_selected ? '*' : ' ');
+    if (target && target->GetDebugger().GetUseExternalEditor()) {
+      StackFrameSP frame_sp = GetStackFrameAtIndex(start_frame);
+      if (frame_sp) {
+        SymbolContext frame_sc(
+            frame_sp->GetSymbolContext(eSymbolContextLineEntry));
+        if (frame_sc.line_entry.line != 0 && frame_sc.line_entry.file) {
+          Host::OpenFileInExternalEditor(frame_sc.line_entry.file,
+                                         frame_sc.line_entry.line);
+        }
       }
     }
-  }
 
-  DumpUsingSettingsFormat(strm, start_frame, stop_format);
+    DumpUsingSettingsFormat(strm, start_frame, stop_format);
+  }
 
+  size_t num_frames_shown = 0;
   if (num_frames > 0) {
     strm.IndentMore();
 
     const bool show_frame_info = true;
-
+    const bool show_frame_unique = only_stacks;
     const char *selected_frame_marker = nullptr;
-    if (num_frames == 1 ||
+    if (num_frames == 1 || only_stacks ||
         (GetID() != GetProcess()->GetThreadList().GetSelectedThread()->GetID()))
       strm.IndentMore();
     else
       selected_frame_marker = "* ";
 
     num_frames_shown = GetStackFrameList()->GetStatus(
         strm, start_frame, num_frames, show_frame_info, num_frames_with_source,
-        selected_frame_marker);
+        show_frame_unique, selected_frame_marker);
     if (num_frames == 1)
       strm.IndentLess();
     strm.IndentLess();