[trace][intelpt] Introduce instruction Ids

[wallace]

Summary

In order to support quick arbitrary access to instructions in the trace, we need
each instruction to have an id. It could be an index or any other value that the
trace plugin defines.

This will be useful for reverse debugging or for creating callstacks, as each
frame will need an instruction id associated with them.

I've updated the thread trace dump instructions command accordingly. It now
prints the instruction id instead of relative offset. I've also added a new --id
argument that allows starting the dump from an arbitrary position.

[jj10306]

Couple minor things

lldb/include/lldb/Target/TraceInstructionDumper.h

66

lldb/source/Plugins/Trace/intel-pt/TraceCursorIntelPT.cpp

54

Should this return an unsigned int? Currently, it appears the return value will always be >= 0

lldb/source/Target/TraceInstructionDumper.cpp

33

nit: Given that we have SeekType::End, why not rename SeekType::Set, to SeekType::Start? SeekType::Set was a little confusing to me the first time I read it.

[wallace]

address comments

[jj10306]

nice work!

[clayborg]

lldb/include/lldb/Target/TraceCursor.h

210–213

might be nice to clarify this definition a bit with info like:

• does this need to be unique only within a single thread or does it need to be unique globally for any instruction in any thread within the process?
• a bit of info on why this is needed and what it will be used for as this will help people know how to create it so they can make sure it is efficient.

214

lldb/include/lldb/Target/TraceInstructionDumper.h

44–47

Since we are adding new options, and if this is going to go in the public API at some point, it might be nice to make a "TraceInstructionDumperOptions class which default constructs with good default values. This way when you need to add a new option, it won't change the API

lldb/source/Commands/CommandObjectThread.cpp

2171–2177

use TraceInstructionDumperOptions?

2187–2193

Use TraceInstructionDumperOptions?

lldb/source/Plugins/Trace/intel-pt/TraceCursorIntelPT.cpp

105

112

lldb/source/Plugins/Trace/intel-pt/TraceCursorIntelPT.h

38

40

[wallace]

• improve documentation
• use lldb::user_id_t
• add the new TraceInstructionDumperOptions struct

[wallace]

nits

[clayborg]

lldb/include/lldb/Target/TraceCursor.h

161–165

fix wrap here. Might have been a clang format change

lldb/include/lldb/Target/TraceInstructionDumper.h

39

Do we want the stream in the options?

lldb/source/Commands/Options.td

1126–1129

this option might not be needed. Each LLDB command line command can save information for how to continue a subsequent command. For example:

(lldb) memory read $pc
0x100002ecf: 48 8d 7d f0 48 8d 35 a6 ff ff ff e8 51 00 00 00  H.}.H.5.....Q...
0x100002edf: c7 45 ec 01 00 00 00 8b 75 ec 48 8d 3d 1e 10 00  .E......u.H.=...
(lldb) 
0x100002eef: 00 31 c0 e8 f5 0e 00 00 e9 00 00 00 00 e9 00 00  .1..............
0x100002eff: 00 00 8b 45 ec 83 c0 01 89 45 ec e9 d7 ff ff ff  ...E.....E......
(lldb) 
0x100002f0f: 48 89 c1 89 d0 48 89 4d e0 89 45 dc 48 8d 7d f0  H....H.M..E.H.}.
0x100002f1f: e8 aa 0e 00 00 48 8b 7d e0 e8 7d 0e 00 00 0f 1f  .....H.}..}.....

Note that I just hit enter after the first read memory. Can we just take advantage of this feature instead of addind the "--continue" option?

lldb/source/Target/TraceInstructionDumper.cpp

28

When there is no formatter, you can just use Stream::PutCString(...)

[wallace]

fix some comments

[wallace]

lldb/include/lldb/Target/TraceInstructionDumper.h

39

we can't do it nicely, because we are adding a TraceInstructionDumper variable in CommandObjectTraceDumpInstructions::CommandOptions, where we don't have a stream available. I imagine this being the only variable that we can't put in the options, so it should be okay

[wallace]

Some updates:

• Modified thread trace dump instructions to accept one single thread instead of many. The reason is that, with the new --id argument, traversing multiple threads doesn't make sense anymore, as the id might only exist in one single thread. Besides that, it's really not very useful to analyze multiple threads in parallel by chunks. You normally want to analyze one of them at a time.
• I couldn't find a simple way to create the repeat command directly from GetRepeatCommand because it's not easy to quickly find what the next instruction is going to be in the repeat command. In fact, finding the id of that future instruction requires to actually traverse the instructions up to that point, but the traversal only happens in DoExecute, which is invoked after GetRepeatCommand. As a simple workarou nd, I'm adding a " repeat" positional argument that won't be parsed by CommandOptions but will still indicate that a repeat is happening. I was able to remove the --continue flag from Options.td, thus reducing the amount of code needed to handle the repeat. Not only that, I was able to get rid of the map<tid, TraceInstructionDumper> that I had in the CommandObject that I was using to continue the iteration in the repeat commands. Now I'm using the last iterated id to computed where the next one will be, thus creating a new brand new dumper with each command making this class simpler.
• I can't pass the Stream to TraceInstructionDumperOptions because when that object is crea ted the Stream is not yet available.

[clayborg]

lldb/source/Commands/CommandObjectThread.cpp

2218

This " repeat" is pretty hacky here. If we can't get away without adding anything, I would prefer the --continue option we had before

2256–2258

to make repeat work, you are filling in the dumper options, can't we just store a copy of the old thread options and update the "id" field?

You also mentioned:

I couldn't find a simple way to create the repeat command directly from GetRepeatCommand because it's not easy to quickly find what the next instruction is going to be in the repeat command. In fact, finding the id of that future instruction requires to actually traverse the instructions up to that point, but the traversal only happens in DoExecute, which is invoked after GetRepeatCommand. As a simple workarou nd, I'm adding a " repeat" positional argument that won't be parsed by CommandOptions but will still indicate that a repeat is happening. I was able to remove the --continue flag from Options.td, thus reducing the amount of code needed to handle the repeat. Not only that, I was able to get rid of the map<tid, TraceInstructionDumper> that I had in the CommandObject that I was using to continue the iteration in the repeat commands. Now I'm using the last iterated id to computed where the next one will be, thus creating a new brand new dumper with each command making this class simpler.

You seem to have the right "id" to start at here with m_last_id? Why can't we just store this in an extra copy of TraceInstructionDumperOptions and have it create the right command?

[wallace]

• Bring back the --continue command.

lldb/include/lldb/Target/TraceCursor.h

public:
   ///     How many items to move forwards (if positive) or backwards (if
   ///     negative) from the given origin point.
   ///
   /// \param[in] origin
   ///     The reference point to use when moving the cursor.
   ///
   /// \return
   ///     The number of trace items moved from the origin.
-  virtual size_t Seek(ssize_t offset, SeekType origin) = 0;
+  virtual int64_t Seek(int64_t offset, SeekType origin) = 0;
+
+  /// Make the cursor point to the item whose identifier is \p id. See \a
+  /// Trace::GetId() for more information.
+  ///
+  /// \return
+  ///     \b true if the given identifier exists and the cursor effectively
+  ///     moved, \b false otherwise.
+  virtual bool GoToId(uint64_t id) = 0;
 
   /// \return
   ///   The \a ExecutionContextRef of the backing thread from the creation time
   ///   of this cursor.
   ExecutionContextRef &GetExecutionContextRef();
 
   /// Instruction or error information
   /// \{
 
   /// \return
public:
   virtual llvm::Optional<uint64_t> GetCounter(lldb::TraceCounter counter_type) = 0;
 
   /// \return
   ///     The \a lldb::TraceInstructionControlFlowType categories the
   ///     instruction the cursor is pointing at falls into. If the cursor points
   ///     to an error in the trace, return \b 0.
   virtual lldb::TraceInstructionControlFlowType
   GetInstructionControlFlowType() = 0;
+
+  /// \return
+  ///     A unique identifier for the instruction or error this cursor is
+  ///     pointing to. Each Trace plug-in can decide the nature of these
+  ///     identifiers and thus no assumptions can be made regarding its ordering
+  ///     and sequentiality.
+  virtual uint64_t GetId() const = 0;
   /// \}
 
 protected:
   ExecutionContextRef m_exe_ctx_ref;
 
   lldb::TraceInstructionControlFlowType m_granularity =
       lldb::eTraceInstructionControlFlowTypeInstruction;
   bool m_ignore_errors = false;
   bool m_forwards = false;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_TARGET_TRACE_CURSOR_H

lldb/include/lldb/Target/TraceInstructionDumper.h

 /// state and granularity.
 class TraceInstructionDumper {
 public:
   /// Create a instruction dumper for the cursor.
   ///
   /// \param[in] cursor
   ///     The cursor whose instructions will be dumped.
   ///
-  /// \param[in] initial_index
-  ///     Presentation index to use for referring to the current instruction
-  ///     of the cursor. If the direction is forwards, the index will increase,
-  ///     and if the direction is backwards, the index will decrease.
+  /// \param[in] forwards
+  ///     If \b true, the cursor will be iterated forwards starting from the
+  ///     oldest instruction. Otherwise, the iteration starts from the most
+  ///     recent instruction.
   ///
   /// \param[in] raw
   ///     Dump only instruction addresses without disassembly nor symbol
   ///     information.
   ///
   /// \param[in] show_tsc
   ///     For each instruction, print the corresponding timestamp counter if
   ///     available.
-  TraceInstructionDumper(lldb::TraceCursorUP &&cursor_up, int initial_index = 0,
-                         bool raw = false, bool show_tsc = false);
+  ///
+  /// \param[in] id
+  ///     Optional custom id to start traversing from.
+  ///
+  /// \param[in] skip
+  ///     Optional number of instructions to skip from the starting position
+  ///     of the cursor.
+  TraceInstructionDumper(lldb::TraceCursorUP &&cursor_up, bool forwards,
+                         bool raw, bool show_tsc, llvm::Optional<uint64_t> id,
+                         llvm::Optional<size_t> skip, Stream &s);
 
   /// Dump \a count instructions of the thread trace starting at the current
   /// cursor position.
   ///
   /// This effectively moves the cursor to the next unvisited position, so that
   /// a subsequent call to this method continues where it left off.
   ///
   /// \param[in] s
   ///     The stream object where the instructions are printed.
   ///
   /// \param[in] count
   ///     The number of instructions to print.
   void DumpInstructions(Stream &s, size_t count);
 
-  /// Indicate the dumper that no more data is available in the trace.
-  void SetNoMoreData();
-
   /// \return
   ///     \b true if there's still more data to traverse in the trace.
   bool HasMoreData();
 
 private:
+  /// Indicate the dumper that no more data is available in the trace.
+  /// This will prevent further iterations.
+  void SetNoMoreData();
+
   /// Move the cursor one step.
   ///
   /// \return
   ///     \b true if the cursor moved.
   bool TryMoveOneStep();
 
   lldb::TraceCursorUP m_cursor_up;
-  int m_index;
   bool m_raw;
   bool m_show_tsc;
   /// If \b true, all the instructions have been traversed.
   bool m_no_more_data = false;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_TARGET_TRACE_INSTRUCTION_DUMPER_H

lldb/source/Commands/CommandObjectThread.cpp

Status SetOptionValue(uint32_t option_idx, llvm::StringRef option_arg,
         if (option_arg.empty() || option_arg.getAsInteger(0, skip) || skip < 0)
           error.SetErrorStringWithFormat(
               "invalid integer value for option '%s'",
               option_arg.str().c_str());
         else
           m_skip = skip;
         break;
       }
+      case 'i': {
+        uint64_t id;
+        if (option_arg.empty() || option_arg.getAsInteger(0, id))
+          error.SetErrorStringWithFormat(
+              "invalid integer value for option '%s'",
+              option_arg.str().c_str());
+        else
+          m_id = id;
+        break;
+      }
       case 'r': {
         m_raw = true;
         break;
       }
       case 'f': {
         m_forwards = true;
         break;
       }
       case 't': {
         m_show_tsc = true;
         break;
       }
       case 'C': {
         m_continue = true;
         break;
       }
       default:
         llvm_unreachable("Unimplemented option");
       }
       return error;
     }
 
     void OptionParsingStarting(ExecutionContext *execution_context) override {
       m_count = kDefaultCount;
-      m_skip = 0;
+      m_skip = llvm::None;
+      m_id = llvm::None;
       m_raw = false;
       m_forwards = false;
       m_show_tsc = false;
       m_continue = false;
     }
 
     llvm::ArrayRef<OptionDefinition> GetDefinitions() override {
       return llvm::makeArrayRef(g_thread_trace_dump_instructions_options);
     }
 
     static const size_t kDefaultCount = 20;
 
     // Instance variables to hold the values for command options.
     size_t m_count;
-    size_t m_skip;
+    llvm::Optional<size_t> m_skip;
+    llvm::Optional<uint64_t> m_id;
     bool m_raw;
     bool m_forwards;
     bool m_show_tsc;
     bool m_continue;
   };
 
   CommandObjectTraceDumpInstructions(CommandInterpreter &interpreter)
       : CommandObjectIterateOverThreads(
             interpreter, "thread trace dump instructions",
             "Dump the traced instructions for one or more threads. If no "
             "threads are specified, show the current thread. Use the "
             "thread-index \"all\" to see all threads.",
             nullptr,
             eCommandRequiresProcess | eCommandTryTargetAPILock |
                 eCommandProcessMustBeLaunched | eCommandProcessMustBePaused |
                 eCommandProcessMustBeTraced) {}
 
   ~CommandObjectTraceDumpInstructions() override = default;
 
   Options *GetOptions() override { return &m_options; }
 
   llvm::Optional<std::string> GetRepeatCommand(Args &current_command_args,
                                                uint32_t index) override {
     std::string cmd;
     current_command_args.GetCommandString(cmd);
     if (cmd.find("--continue") == std::string::npos)
       cmd += " --continue";
     return cmd;
   }
 
 protected:
   bool DoExecute(Args &args, CommandReturnObject &result) override {
     if (!m_options.m_continue)
       m_dumpers.clear();
 
     return CommandObjectIterateOverThreads::DoExecute(args, result);
   }
 
+  TraceInstructionDumper &GetOrCreateDumper(TraceSP trace_sp,
+                                            ThreadSP thread_sp, Stream &s) {
+    // We already have a cursor for this thread
+    auto it = m_dumpers.find(thread_sp->GetID());
+    if (it != m_dumpers.end())
+      return *it->second;
+
+    auto dumper = std::make_unique<TraceInstructionDumper>(
+        trace_sp->GetCursor(*thread_sp), m_options.m_forwards, m_options.m_raw,
+        m_options.m_show_tsc, m_options.m_id, m_options.m_skip, s);
+
+    return *m_dumpers.emplace(thread_sp->GetID(), std::move(dumper))
+                .first->second;
+  }
+
   bool HandleOneThread(lldb::tid_t tid, CommandReturnObject &result) override {
     Stream &s = result.GetOutputStream();
 
     const TraceSP &trace_sp = m_exe_ctx.GetTargetSP()->GetTrace();
     ThreadSP thread_sp =
         m_exe_ctx.GetProcessPtr()->GetThreadList().FindThreadByID(tid);
 
-    if (!m_dumpers.count(thread_sp->GetID())) {
-      lldb::TraceCursorUP cursor_up = trace_sp->GetCursor(*thread_sp);
-      // Set up the cursor and return the presentation index of the first
-      // instruction to dump after skipping instructions.
-      auto setUpCursor = [&]() {
-        cursor_up->SetForwards(m_options.m_forwards);
-        if (m_options.m_forwards)
-          return cursor_up->Seek(m_options.m_skip, TraceCursor::SeekType::Set);
-        return -cursor_up->Seek(-m_options.m_skip, TraceCursor::SeekType::End);
-      };
-
-      int initial_index = setUpCursor();
-
-      auto dumper = std::make_unique<TraceInstructionDumper>(
-          std::move(cursor_up), initial_index, m_options.m_raw,
-          m_options.m_show_tsc);
-
-      // This happens when the seek value was more than the number of available
-      // instructions.
-      if (std::abs(initial_index) < (int)m_options.m_skip)
-        dumper->SetNoMoreData();
-
-      m_dumpers[thread_sp->GetID()] = std::move(dumper);
-    }
-
-    m_dumpers[thread_sp->GetID()]->DumpInstructions(s, m_options.m_count);
+    GetOrCreateDumper(trace_sp, thread_sp, s)
+        .DumpInstructions(s, m_options.m_count);
     return true;
   }
 
   CommandOptions m_options;
   std::map<lldb::tid_t, std::unique_ptr<TraceInstructionDumper>> m_dumpers;
 };
 
 // CommandObjectTraceDumpInfo
 #define LLDB_OPTIONS_thread_trace_dump_info
 #include "CommandOptions.inc"
 
 class CommandObjectTraceDumpInfo : public CommandObjectIterateOverThreads {
 public:
   class CommandOptions : public Options {
   public:

lldb/source/Commands/Options.td

let Command = "thread plan list" in {
   def thread_plan_list_thread_id : Option<"thread-id", "t">, Group<1>,
     Arg<"ThreadID">, Desc<"List the thread plans for this TID, can be "
     "specified more than once.">;
   def thread_plan_list_unreported : Option<"unreported", "u">, Group<1>,
     Desc<"Display thread plans for unreported threads">;
 }
 
 let Command = "thread trace dump instructions" in {
-  def thread_trace_dump_instructions_forwards: Option<"forwards", "f">, Group<1>,
+  def thread_trace_dump_instructions_forwards: Option<"forwards", "f">,
+    Group<1>,
     Desc<"If specified, the trace is traversed forwards chronologically "
     "starting at the oldest instruction. Otherwise, it starts at the most "
     "recent one and the traversal is backwards.">;
   def thread_trace_dump_instructions_count : Option<"count", "c">, Group<1>,
     Arg<"Count">,
     Desc<"The number of instructions to display starting at the most recent "
     "instruction, or the oldest if --forwards is provided.">;
-  def thread_trace_dump_instructions_skip: Option<"skip", "s">,
-    Group<1>,
+  def thread_trace_dump_instructions_id: Option<"id", "i">, Group<1>,
     Arg<"Index">,
-    Desc<"How many instruction to skip from the end of the trace to start "
-    "dumping instructions, or from the beginning if --forwards is provided">;
+    Desc<"Custom starting instruction id from where to start traversing. This "
+    "id can be provided in decimal or hexadecimal representation.">;
+  def thread_trace_dump_instructions_skip: Option<"skip", "s">, Group<1>,
+    Arg<"Index">,
+    Desc<"How many instruction to skip from the starting position of the trace "
+    "before starting the traversal.">;
   def thread_trace_dump_instructions_raw : Option<"raw", "r">,
     Group<1>,
-    Desc<"Dump only instruction address without disassembly nor symbol information.">;
-  def thread_trace_dump_instructions_show_tsc : Option<"tsc", "t">,
-    Group<1>,
-    Desc<"For each instruction, print the corresponding timestamp counter if available.">;
+    Desc<"Dump only instruction address without disassembly nor symbol "
+    "information.">;
+  def thread_trace_dump_instructions_show_tsc : Option<"tsc", "t">, Group<1>,
+    Desc<"For each instruction, print the corresponding timestamp counter if "
+    "available.">;
   def thread_trace_dump_instructions_continue: Option<"continue", "C">,
     Group<1>,
-    Desc<"Continue dumping instructions right where the previous invocation of this "
-    "command was left, or from the beginning if this is the first invocation. The --skip "
-    "argument is discarded and the other arguments are preserved from the previous "
-    "invocation when possible.">;
+    Desc<"Continue dumping instructions right where the previous invocation of "
+    "this command was left, or from the beginning if this is the first "
+    "invocation. The --skip and --id arguments are discared if provided.">;
 }
 
 let Command = "thread trace dump info" in {
   def thread_trace_dump_info_verbose : Option<"verbose", "v">, Group<1>,
     Desc<"show verbose thread trace dump info">;
 }
 
 let Command = "type summary add" in {
   def type_summary_add_category : Option<"category", "w">, Arg<"Name">,

lldb/source/Plugins/Trace/intel-pt/TraceCursorIntelPT.h

 namespace lldb_private {
 namespace trace_intel_pt {
 
 class TraceCursorIntelPT : public TraceCursor {
 public:
   TraceCursorIntelPT(lldb::ThreadSP thread_sp,
                      DecodedThreadSP decoded_thread_sp);
 
-  size_t Seek(int64_t offset, SeekType origin) override;
+  int64_t Seek(int64_t offset, SeekType origin) override;
 
   virtual bool Next() override;
 
   llvm::Error GetError() override;
 
   lldb::addr_t GetLoadAddress() override;
 
   llvm::Optional<uint64_t> GetCounter(lldb::TraceCounter counter_type) override;
 
   lldb::TraceInstructionControlFlowType
   GetInstructionControlFlowType() override;
 
   bool IsError() override;
 
+  bool GoToId(uint64_t id) override;
+
+  uint64_t GetId() const override;
+
 private:
   size_t GetInternalInstructionSize();
 
   /// Storage of the actual instructions
   DecodedThreadSP m_decoded_thread_sp;
   /// Internal instruction index currently pointing at.
   size_t m_pos;
 };
 
 } // namespace trace_intel_pt
 } // namespace lldb_private
 
 #endif // LLDB_SOURCE_PLUGINS_TRACE_INTEL_PT_TRACECURSORINTELPT_H

lldb/source/Plugins/Trace/intel-pt/TraceCursorIntelPT.cpp

if (GetInstructionControlFlowType() & m_granularity)
       return true;
   }
 
   // Didn't find any matching instructions
   m_pos = initial_pos;
   return false;
 }
 
-size_t TraceCursorIntelPT::Seek(int64_t offset, SeekType origin) {
+int64_t TraceCursorIntelPT::Seek(int64_t offset, SeekType origin) {
   int64_t last_index = GetInternalInstructionSize() - 1;
 
   auto fitPosToBounds = [&](int64_t raw_pos) -> int64_t {
     return std::min(std::max((int64_t)0, raw_pos), last_index);
   };
 
   switch (origin) {
   case TraceCursor::SeekType::Set:

 TraceCursorIntelPT::GetInstructionControlFlowType() {
   lldb::addr_t next_load_address =
       m_pos + 1 < GetInternalInstructionSize()
           ? m_decoded_thread_sp->GetInstructions()[m_pos + 1].GetLoadAddress()
           : LLDB_INVALID_ADDRESS;
   return m_decoded_thread_sp->GetInstructions()[m_pos].GetControlFlowType(
       next_load_address);
 }
+
+bool TraceCursorIntelPT::GoToId(uint64_t id) {
+  if (m_decoded_thread_sp->GetInstructions().size() <= id)
+    return false;
+  m_pos = id;
+  return true;
+}
+
+uint64_t TraceCursorIntelPT::GetId() const { return m_pos; }

lldb/source/Plugins/Trace/intel-pt/TraceIntelPT.cpp

void TraceIntelPT::DumpTraceInfo(Thread &thread, Stream &s, bool verbose) {
   s.Printf("\n");
 
   size_t mem_used = Decode(thread)->CalculateApproximateMemoryUsage();
   s.Printf("  Raw trace size: %zu KiB\n", *raw_size / 1024);
   s.Printf("  Total number of instructions: %zu\n",
            Decode(thread)->GetInstructions().size());
   s.Printf("  Total approximate memory usage: %0.2lf KiB\n",
            (double)mem_used / 1024);
-  return;
 }
 
 Optional<size_t> TraceIntelPT::GetRawTraceSize(Thread &thread) {
   if (IsTraced(thread.GetID()))
     return Decode(thread)->GetRawTraceSize();
   else
     return None;
 }

lldb/source/Target/TraceInstructionDumper.cpp

 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/SectionLoadList.h"
 
 using namespace lldb;
 using namespace lldb_private;
 using namespace llvm;
 
-TraceInstructionDumper::TraceInstructionDumper(lldb::TraceCursorUP &&cursor_up,
-                                               int initial_index, bool raw,
-                                               bool show_tsc)
-    : m_cursor_up(std::move(cursor_up)), m_index(initial_index), m_raw(raw),
-      m_show_tsc(show_tsc) {}
+TraceInstructionDumper::TraceInstructionDumper(
+    lldb::TraceCursorUP &&cursor_up, bool forwards, bool raw, bool show_tsc,
+    llvm::Optional<uint64_t> id, llvm::Optional<size_t> skip, Stream &s)
+    : m_cursor_up(std::move(cursor_up)), m_raw(raw), m_show_tsc(show_tsc) {
+  // We first set the cursor in its initial position
+  if (id) {
+    if (!m_cursor_up->GoToId(*id)) {
+      s.Printf("    invalid instruction id\n");
+      SetNoMoreData();
+      return;
+    }
+  } else if (forwards) {
+    m_cursor_up->Seek(0, TraceCursor::SeekType::Set);
+  } else {
+    m_cursor_up->Seek(0, TraceCursor::SeekType::End);
+  }
+
+  m_cursor_up->SetForwards(forwards);
+  if (skip) {
+    int64_t to_skip = skip.getValue();
+    if (m_cursor_up->Seek((forwards ? 1 : -1) * to_skip,
+                          TraceCursor::SeekType::Current) < to_skip) {
+      // This happens when the skip value was more than the number of
+      // available instructions.
+      SetNoMoreData();
+    }
+  }
+}
 
 /// \return
 ///     Return \b true if the cursor could move one step.
 bool TraceInstructionDumper::TryMoveOneStep() {
   if (!m_cursor_up->Next()) {
     SetNoMoreData();
     return false;
   }
-  m_index += m_cursor_up->IsForwards() ? 1 : -1;
   return true;
 }
 
-/// \return
-///     The number of characters that would be needed to print the given
-///     integer.
-static int GetNumberOfChars(int num) {
-  if (num == 0)
-    return 1;
-  return (num < 0 ? 1 : 0) + static_cast<int>(log10(abs(num))) + 1;
-}
-
 /// Helper struct that holds symbol, disassembly and address information of an
 /// instruction.
 struct InstructionSymbolInfo {
   SymbolContext sc;
   Address address;
   lldb::addr_t load_address;
   lldb::DisassemblerSP disassembler;
   lldb::InstructionSP instruction;
void TraceInstructionDumper::DumpInstructions(Stream &s, size_t count) {
   if (!thread_sp) {
     s.Printf("invalid thread");
     return;
   }
 
   s.Printf("thread #%u: tid = %" PRIu64 "\n", thread_sp->GetIndexID(),
            thread_sp->GetID());
 
-  int digits_count = GetNumberOfChars(
-      m_cursor_up->IsForwards() ? m_index + count - 1 : m_index - count + 1);
   bool was_prev_instruction_an_error = false;
 
   auto printMissingInstructionsMessage = [&]() {
     s.Printf("    ...missing instructions\n");
   };
 
-  auto printInstructionIndex = [&]() {
-    s.Printf("    [%*d] ", digits_count, m_index);
+  auto printInstructionHeader = [&](uint64_t id) {
+    s.Printf("    %" PRIu64 ": ", id);
 
     if (m_show_tsc) {
       s.Printf("[tsc=");
 
       if (Optional<uint64_t> timestamp = m_cursor_up->GetCounter(lldb::eTraceCounterTSC))
         s.Printf("0x%016" PRIx64, *timestamp);
       else
         s.Printf("unavailable");
for (size_t i = 0; i < count; i++) {
     }
 
     if (Error err = m_cursor_up->GetError()) {
       if (!m_cursor_up->IsForwards() && !was_prev_instruction_an_error)
         printMissingInstructionsMessage();
 
       was_prev_instruction_an_error = true;
 
-      printInstructionIndex();
+      printInstructionHeader(m_cursor_up->GetId());
       s << toString(std::move(err));
     } else {
       if (m_cursor_up->IsForwards() && was_prev_instruction_an_error)
         printMissingInstructionsMessage();
 
       was_prev_instruction_an_error = false;
 
       InstructionSymbolInfo insn_info;
 
       if (!m_raw) {
         insn_info.load_address = m_cursor_up->GetLoadAddress();
         insn_info.exe_ctx = exe_ctx;
         insn_info.address.SetLoadAddress(insn_info.load_address, &target);
         insn_info.sc = calculateSymbolContext(insn_info.address);
         std::tie(insn_info.disassembler, insn_info.instruction) =
             calculateDisass(insn_info.address, insn_info.sc);
 
         DumpInstructionSymbolContext(s, prev_insn_info, insn_info);
       }
 
-      printInstructionIndex();
+      printInstructionHeader(m_cursor_up->GetId());
       s.Printf("0x%016" PRIx64, m_cursor_up->GetLoadAddress());
 
       if (!m_raw)
         DumpInstructionDisassembly(s, insn_info);
 
       prev_insn_info = insn_info;
     }
 
     s.Printf("\n");
     TryMoveOneStep();
   }
 }

lldb/test/API/commands/trace/TestTraceDumpInstructions.py

class TestTraceDumpInstructions(TraceIntelPTTestCaseBase):
 
     def testRawDumpInstructions(self):
         self.expect("trace load -v " +
             os.path.join(self.getSourceDir(), "intelpt-trace", "trace.json"),
             substrs=["intel-pt"])
 
         self.expect("thread trace dump instructions --raw --count 21 --forwards",
             substrs=['''thread #1: tid = 3842849
-    [ 0] 0x0000000000400511
-    [ 1] 0x0000000000400518
-    [ 2] 0x000000000040051f
-    [ 3] 0x0000000000400529
-    [ 4] 0x000000000040052d
-    [ 5] 0x0000000000400521
-    [ 6] 0x0000000000400525
-    [ 7] 0x0000000000400529
-    [ 8] 0x000000000040052d
-    [ 9] 0x0000000000400521
-    [10] 0x0000000000400525
-    [11] 0x0000000000400529
-    [12] 0x000000000040052d
-    [13] 0x0000000000400521
-    [14] 0x0000000000400525
-    [15] 0x0000000000400529
-    [16] 0x000000000040052d
-    [17] 0x0000000000400521
-    [18] 0x0000000000400525
-    [19] 0x0000000000400529
-    [20] 0x000000000040052d'''])
+    0: 0x0000000000400511
+    1: 0x0000000000400518
+    2: 0x000000000040051f
+    3: 0x0000000000400529
+    4: 0x000000000040052d
+    5: 0x0000000000400521
+    6: 0x0000000000400525
+    7: 0x0000000000400529
+    8: 0x000000000040052d
+    9: 0x0000000000400521
+    10: 0x0000000000400525
+    11: 0x0000000000400529
+    12: 0x000000000040052d
+    13: 0x0000000000400521
+    14: 0x0000000000400525
+    15: 0x0000000000400529
+    16: 0x000000000040052d
+    17: 0x0000000000400521
+    18: 0x0000000000400525
+    19: 0x0000000000400529
+    20: 0x000000000040052d'''])
 
         # We check if we can pass count and skip
         self.expect("thread trace dump instructions --count 5 --skip 6 --raw --forwards",
             substrs=['''thread #1: tid = 3842849
-    [ 6] 0x0000000000400525
-    [ 7] 0x0000000000400529
-    [ 8] 0x000000000040052d
-    [ 9] 0x0000000000400521
-    [10] 0x0000000000400525'''])
+    6: 0x0000000000400525
+    7: 0x0000000000400529
+    8: 0x000000000040052d
+    9: 0x0000000000400521
+    10: 0x0000000000400525'''])
 
         self.expect("thread trace dump instructions --count 5 --skip 6 --raw",
             substrs=['''thread #1: tid = 3842849
-    [ -6] 0x0000000000400525
-    [ -7] 0x0000000000400521
-    [ -8] 0x000000000040052d
-    [ -9] 0x0000000000400529
-    [-10] 0x0000000000400525'''])
+    14: 0x0000000000400525
+    13: 0x0000000000400521
+    12: 0x000000000040052d
+    11: 0x0000000000400529
+    10: 0x0000000000400525'''])
+
+        # We check if we can pass count and skip and instruction id in hex
+        self.expect("thread trace dump instructions --count 5 --skip 6 --raw --id 0xA",
+            substrs=['''thread #1: tid = 3842849
+    4: 0x000000000040052d
+    3: 0x0000000000400529
+    2: 0x000000000040051f
+    1: 0x0000000000400518
+    0: 0x0000000000400511'''])
+
+        # We check if we can pass count and skip and instruction id in decimal
+        self.expect("thread trace dump instructions --count 5 --skip 6 --raw --id 10",
+            substrs=['''thread #1: tid = 3842849
+    4: 0x000000000040052d
+    3: 0x0000000000400529
+    2: 0x000000000040051f
+    1: 0x0000000000400518
+    0: 0x0000000000400511'''])
 
         # We check if we can access the thread by index id
         self.expect("thread trace dump instructions 1 --raw",
             substrs=['''thread #1: tid = 3842849
-    [  0] 0x000000000040052d'''])
+    20: 0x000000000040052d'''])
 
         # We check that we get an error when using an invalid thread index id
         self.expect("thread trace dump instructions 10", error=True,
             substrs=['error: no thread with index: "10"'])
 
     def testDumpFullInstructionsWithMultipleThreads(self):
         # We load a trace with two threads
         self.expect("trace load -v " +
             os.path.join(self.getSourceDir(), "intelpt-trace", "trace_2threads.json"))
 
         # We print the instructions of two threads simultaneously
         self.expect("thread trace dump instructions 1 2 --count 2",
             substrs=['''thread #1: tid = 3842849
   a.out`main + 32 at main.cpp:4
-    [ 0] 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
-    [-1] 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)
+    20: 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
+    19: 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)
 thread #2: tid = 3842850
   a.out`main + 32 at main.cpp:4
-    [ 0] 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
-    [-1] 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)'''])
+    20: 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
+    19: 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)'''])
 
         # We use custom --count and --skip, saving the command to history for later
         self.expect("thread trace dump instructions 1 2 --count 2 --skip 2", inHistory=True,
             substrs=['''thread #1: tid = 3842849
   a.out`main + 24 at main.cpp:4
-    [-2] 0x0000000000400525    addl   $0x1, -0x8(%rbp)
+    18: 0x0000000000400525    addl   $0x1, -0x8(%rbp)
   a.out`main + 20 at main.cpp:5
-    [-3] 0x0000000000400521    xorl   $0x1, -0x4(%rbp)
+    17: 0x0000000000400521    xorl   $0x1, -0x4(%rbp)
 thread #2: tid = 3842850
   a.out`main + 24 at main.cpp:4
-    [-2] 0x0000000000400525    addl   $0x1, -0x8(%rbp)
+    18: 0x0000000000400525    addl   $0x1, -0x8(%rbp)
   a.out`main + 20 at main.cpp:5
-    [-3] 0x0000000000400521    xorl   $0x1, -0x4(%rbp)'''])
+    17: 0x0000000000400521    xorl   $0x1, -0x4(%rbp)'''])
 
         # We use a repeat command twice and ensure the previous count is used and the
         # start position moves with each command.
         self.expect("", inHistory=True,
             substrs=['''thread #1: tid = 3842849
   a.out`main + 32 at main.cpp:4
-    [-4] 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
-    [-5] 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)
+    16: 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
+    15: 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)
 thread #2: tid = 3842850
   a.out`main + 32 at main.cpp:4
-    [-4] 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
-    [-5] 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)'''])
+    16: 0x000000000040052d    jle    0x400521                  ; <+20> at main.cpp:5
+    15: 0x0000000000400529    cmpl   $0x3, -0x8(%rbp)'''])
 
         self.expect("", inHistory=True,
             substrs=['''thread #1: tid = 3842849
   a.out`main + 24 at main.cpp:4
-    [-6] 0x0000000000400525    addl   $0x1, -0x8(%rbp)
+    14: 0x0000000000400525    addl   $0x1, -0x8(%rbp)
   a.out`main + 20 at main.cpp:5
-    [-7] 0x0000000000400521    xorl   $0x1, -0x4(%rbp)
+    13: 0x0000000000400521    xorl   $0x1, -0x4(%rbp)
 thread #2: tid = 3842850
   a.out`main + 24 at main.cpp:4
-    [-6] 0x0000000000400525    addl   $0x1, -0x8(%rbp)
+    14: 0x0000000000400525    addl   $0x1, -0x8(%rbp)
   a.out`main + 20 at main.cpp:5
-    [-7] 0x0000000000400521    xorl   $0x1, -0x4(%rbp)'''])
+    13: 0x0000000000400521    xorl   $0x1, -0x4(%rbp)'''])
 
     def testInvalidBounds(self):
         self.expect("trace load -v " +
             os.path.join(self.getSourceDir(), "intelpt-trace", "trace.json"))
 
         # The output should be work when too many instructions are asked
         self.expect("thread trace dump instructions --count 20 --forwards",
             substrs=['''thread #1: tid = 3842849
   a.out`main + 4 at main.cpp:2
-    [ 0] 0x0000000000400511    movl   $0x0, -0x4(%rbp)
+    0: 0x0000000000400511    movl   $0x0, -0x4(%rbp)
   a.out`main + 11 at main.cpp:4
-    [ 1] 0x0000000000400518    movl   $0x0, -0x8(%rbp)
-    [ 2] 0x000000000040051f    jmp    0x400529                  ; <+28> at main.cpp:4'''])
+    1: 0x0000000000400518    movl   $0x0, -0x8(%rbp)
+    2: 0x000000000040051f    jmp    0x400529                  ; <+28> at main.cpp:4'''])
 
         # Should print no instructions if the position is out of bounds
         self.expect("thread trace dump instructions --skip 23",
             endstr='no more data\n')
 
         # Should fail with negative bounds
         self.expect("thread trace dump instructions --skip -1", error=True)
         self.expect("thread trace dump instructions --count -1", error=True)
 
     def testWrongImage(self):
         self.expect("trace load " +
             os.path.join(self.getSourceDir(), "intelpt-trace", "trace_bad_image.json"))
         self.expect("thread trace dump instructions --forwards",
             substrs=['''thread #1: tid = 3842849
-    [ 0] 0x0000000000400511    error: no memory mapped at this address
-    [ 1] 0x0000000000400518    error: no memory mapped at this address'''])
+    0: 0x0000000000400511    error: no memory mapped at this address
+    1: 0x0000000000400518    error: no memory mapped at this address'''])
 
     def testWrongCPU(self):
         self.expect("trace load " +
             os.path.join(self.getSourceDir(), "intelpt-trace", "trace_wrong_cpu.json"))
         self.expect("thread trace dump instructions --forwards",
             substrs=['''thread #1: tid = 3842849
-    [ 0] error: unknown cpu'''])
+    0: error: unknown cpu'''])
 
     def testMultiFileTraceWithMissingModule(self):
         self.expect("trace load " +
             os.path.join(self.getSourceDir(), "intelpt-trace-multi-file", "multi-file-no-ld.json"))
 
         # This instructions in this test covers the following flow:
         #
         # - The trace starts with a call to libfoo, which triggers the dynamic
         #   linker, but the dynamic linker is not included in the JSON file,
         #   thus the trace reports a set of missing instructions after
         #   instruction [6].
         # - Then, the dump continues in the next synchronization point showing
         #   a call to an inlined function, which is displayed as [inlined].
         # - Finally, a call to libfoo is performed, which invokes libbar inside.
         #
         # Whenever there's a line or symbol change, including the inline case, a
         # line is printed showing the symbol context change.
         #
         # Finally, the instruction disassembly is included in the dump.
         self.expect("thread trace dump instructions --count 50 --forwards",
             substrs=['''thread #1: tid = 815455
   a.out`main + 15 at main.cpp:10
-    [ 0] 0x000000000040066f    callq  0x400540                  ; symbol stub for: foo()
+    0: 0x000000000040066f    callq  0x400540                  ; symbol stub for: foo()
   a.out`symbol stub for: foo()
-    [ 1] 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
-    [ 2] 0x0000000000400546    pushq  $0x2
-    [ 3] 0x000000000040054b    jmp    0x400510
+    1: 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
+    2: 0x0000000000400546    pushq  $0x2
+    3: 0x000000000040054b    jmp    0x400510
   a.out`(none)
-    [ 4] 0x0000000000400510    pushq  0x200af2(%rip)            ; _GLOBAL_OFFSET_TABLE_ + 8
-    [ 5] 0x0000000000400516    jmpq   *0x200af4(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 16
-    [ 6] 0x00007ffff7df1950    error: no memory mapped at this address
+    4: 0x0000000000400510    pushq  0x200af2(%rip)            ; _GLOBAL_OFFSET_TABLE_ + 8
+    5: 0x0000000000400516    jmpq   *0x200af4(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 16
+    6: 0x00007ffff7df1950    error: no memory mapped at this address
     ...missing instructions
   a.out`main + 20 at main.cpp:10
-    [ 7] 0x0000000000400674    movl   %eax, -0xc(%rbp)
+    7: 0x0000000000400674    movl   %eax, -0xc(%rbp)
   a.out`main + 23 at main.cpp:12
-    [ 8] 0x0000000000400677    movl   -0xc(%rbp), %eax
-    [ 9] 0x000000000040067a    addl   $0x1, %eax
-    [10] 0x000000000040067f    movl   %eax, -0xc(%rbp)
+    8: 0x0000000000400677    movl   -0xc(%rbp), %eax
+    9: 0x000000000040067a    addl   $0x1, %eax
+    10: 0x000000000040067f    movl   %eax, -0xc(%rbp)
   a.out`main + 34 [inlined] inline_function() at main.cpp:4
-    [11] 0x0000000000400682    movl   $0x0, -0x4(%rbp)
+    11: 0x0000000000400682    movl   $0x0, -0x4(%rbp)
   a.out`main + 41 [inlined] inline_function() + 7 at main.cpp:5
-    [12] 0x0000000000400689    movl   -0x4(%rbp), %eax
-    [13] 0x000000000040068c    addl   $0x1, %eax
-    [14] 0x0000000000400691    movl   %eax, -0x4(%rbp)
+    12: 0x0000000000400689    movl   -0x4(%rbp), %eax
+    13: 0x000000000040068c    addl   $0x1, %eax
+    14: 0x0000000000400691    movl   %eax, -0x4(%rbp)
   a.out`main + 52 [inlined] inline_function() + 18 at main.cpp:6
-    [15] 0x0000000000400694    movl   -0x4(%rbp), %eax
+    15: 0x0000000000400694    movl   -0x4(%rbp), %eax
   a.out`main + 55 at main.cpp:14
-    [16] 0x0000000000400697    movl   -0xc(%rbp), %ecx
-    [17] 0x000000000040069a    addl   %eax, %ecx
-    [18] 0x000000000040069c    movl   %ecx, -0xc(%rbp)
+    16: 0x0000000000400697    movl   -0xc(%rbp), %ecx
+    17: 0x000000000040069a    addl   %eax, %ecx
+    18: 0x000000000040069c    movl   %ecx, -0xc(%rbp)
   a.out`main + 63 at main.cpp:16
-    [19] 0x000000000040069f    callq  0x400540                  ; symbol stub for: foo()
+    19: 0x000000000040069f    callq  0x400540                  ; symbol stub for: foo()
   a.out`symbol stub for: foo()
-    [20] 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
+    20: 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
   libfoo.so`foo() at foo.cpp:3
-    [21] 0x00007ffff7bd96e0    pushq  %rbp
-    [22] 0x00007ffff7bd96e1    movq   %rsp, %rbp
+    21: 0x00007ffff7bd96e0    pushq  %rbp
+    22: 0x00007ffff7bd96e1    movq   %rsp, %rbp
   libfoo.so`foo() + 4 at foo.cpp:4
-    [23] 0x00007ffff7bd96e4    subq   $0x10, %rsp
-    [24] 0x00007ffff7bd96e8    callq  0x7ffff7bd95d0            ; symbol stub for: bar()
+    23: 0x00007ffff7bd96e4    subq   $0x10, %rsp
+    24: 0x00007ffff7bd96e8    callq  0x7ffff7bd95d0            ; symbol stub for: bar()
   libfoo.so`symbol stub for: bar()
-    [25] 0x00007ffff7bd95d0    jmpq   *0x200a4a(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 32
+    25: 0x00007ffff7bd95d0    jmpq   *0x200a4a(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 32
   libbar.so`bar() at bar.cpp:1
-    [26] 0x00007ffff79d7690    pushq  %rbp
-    [27] 0x00007ffff79d7691    movq   %rsp, %rbp
+    26: 0x00007ffff79d7690    pushq  %rbp
+    27: 0x00007ffff79d7691    movq   %rsp, %rbp
   libbar.so`bar() + 4 at bar.cpp:2
-    [28] 0x00007ffff79d7694    movl   $0x1, -0x4(%rbp)
+    28: 0x00007ffff79d7694    movl   $0x1, -0x4(%rbp)
   libbar.so`bar() + 11 at bar.cpp:3
-    [29] 0x00007ffff79d769b    movl   -0x4(%rbp), %eax
-    [30] 0x00007ffff79d769e    addl   $0x1, %eax
-    [31] 0x00007ffff79d76a3    movl   %eax, -0x4(%rbp)
+    29: 0x00007ffff79d769b    movl   -0x4(%rbp), %eax
+    30: 0x00007ffff79d769e    addl   $0x1, %eax
+    31: 0x00007ffff79d76a3    movl   %eax, -0x4(%rbp)
   libbar.so`bar() + 22 at bar.cpp:4
-    [32] 0x00007ffff79d76a6    movl   -0x4(%rbp), %eax
-    [33] 0x00007ffff79d76a9    popq   %rbp
-    [34] 0x00007ffff79d76aa    retq''',
+    32: 0x00007ffff79d76a6    movl   -0x4(%rbp), %eax
+    33: 0x00007ffff79d76a9    popq   %rbp
+    34: 0x00007ffff79d76aa    retq''',
   '''libfoo.so`foo() + 13 at foo.cpp:4
-    [35] 0x00007ffff7bd96ed    movl   %eax, -0x4(%rbp)
+    35: 0x00007ffff7bd96ed    movl   %eax, -0x4(%rbp)
   libfoo.so`foo() + 16 at foo.cpp:5
-    [36] 0x00007ffff7bd96f0    movl   -0x4(%rbp), %eax
-    [37] 0x00007ffff7bd96f3    addl   $0x1, %eax
-    [38] 0x00007ffff7bd96f8    movl   %eax, -0x4(%rbp)
+    36: 0x00007ffff7bd96f0    movl   -0x4(%rbp), %eax
+    37: 0x00007ffff7bd96f3    addl   $0x1, %eax
+    38: 0x00007ffff7bd96f8    movl   %eax, -0x4(%rbp)
   libfoo.so`foo() + 27 at foo.cpp:6
-    [39] 0x00007ffff7bd96fb    movl   -0x4(%rbp), %eax
-    [40] 0x00007ffff7bd96fe    addq   $0x10, %rsp
-    [41] 0x00007ffff7bd9702    popq   %rbp
-    [42] 0x00007ffff7bd9703    retq''',
+    39: 0x00007ffff7bd96fb    movl   -0x4(%rbp), %eax
+    40: 0x00007ffff7bd96fe    addq   $0x10, %rsp
+    41: 0x00007ffff7bd9702    popq   %rbp
+    42: 0x00007ffff7bd9703    retq''',
   '''a.out`main + 68 at main.cpp:16
-    [43] 0x00000000004006a4    movl   -0xc(%rbp), %ecx
-    [44] 0x00000000004006a7    addl   %eax, %ecx
-    [45] 0x00000000004006a9    movl   %ecx, -0xc(%rbp)'''])
+    43: 0x00000000004006a4    movl   -0xc(%rbp), %ecx
+    44: 0x00000000004006a7    addl   %eax, %ecx
+    45: 0x00000000004006a9    movl   %ecx, -0xc(%rbp)'''])
 
 
         self.expect("thread trace dump instructions --count 50",
             substrs=['''thread #1: tid = 815455
   a.out`main + 73 at main.cpp:16
-    [  0] 0x00000000004006a9    movl   %ecx, -0xc(%rbp)
-    [ -1] 0x00000000004006a7    addl   %eax, %ecx
-    [ -2] 0x00000000004006a4    movl   -0xc(%rbp), %ecx
+    45: 0x00000000004006a9    movl   %ecx, -0xc(%rbp)
+    44: 0x00000000004006a7    addl   %eax, %ecx
+    43: 0x00000000004006a4    movl   -0xc(%rbp), %ecx
   libfoo.so`foo() + 35 at foo.cpp:6
-    [ -3] 0x00007ffff7bd9703    retq''',
-    '''[ -4] 0x00007ffff7bd9702    popq   %rbp
-    [ -5] 0x00007ffff7bd96fe    addq   $0x10, %rsp
-    [ -6] 0x00007ffff7bd96fb    movl   -0x4(%rbp), %eax
+    42: 0x00007ffff7bd9703    retq''',
+    '''41: 0x00007ffff7bd9702    popq   %rbp
+    40: 0x00007ffff7bd96fe    addq   $0x10, %rsp
+    39: 0x00007ffff7bd96fb    movl   -0x4(%rbp), %eax
   libfoo.so`foo() + 24 at foo.cpp:5
-    [ -7] 0x00007ffff7bd96f8    movl   %eax, -0x4(%rbp)
-    [ -8] 0x00007ffff7bd96f3    addl   $0x1, %eax
-    [ -9] 0x00007ffff7bd96f0    movl   -0x4(%rbp), %eax
+    38: 0x00007ffff7bd96f8    movl   %eax, -0x4(%rbp)
+    37: 0x00007ffff7bd96f3    addl   $0x1, %eax
+    36: 0x00007ffff7bd96f0    movl   -0x4(%rbp), %eax
   libfoo.so`foo() + 13 at foo.cpp:4
-    [-10] 0x00007ffff7bd96ed    movl   %eax, -0x4(%rbp)
+    35: 0x00007ffff7bd96ed    movl   %eax, -0x4(%rbp)
   libbar.so`bar() + 26 at bar.cpp:4
-    [-11] 0x00007ffff79d76aa    retq''',
-    '''[-12] 0x00007ffff79d76a9    popq   %rbp
-    [-13] 0x00007ffff79d76a6    movl   -0x4(%rbp), %eax
+    34: 0x00007ffff79d76aa    retq''',
+    '''33: 0x00007ffff79d76a9    popq   %rbp
+    32: 0x00007ffff79d76a6    movl   -0x4(%rbp), %eax
   libbar.so`bar() + 19 at bar.cpp:3
-    [-14] 0x00007ffff79d76a3    movl   %eax, -0x4(%rbp)
-    [-15] 0x00007ffff79d769e    addl   $0x1, %eax
-    [-16] 0x00007ffff79d769b    movl   -0x4(%rbp), %eax
+    31: 0x00007ffff79d76a3    movl   %eax, -0x4(%rbp)
+    30: 0x00007ffff79d769e    addl   $0x1, %eax
+    29: 0x00007ffff79d769b    movl   -0x4(%rbp), %eax
   libbar.so`bar() + 4 at bar.cpp:2
-    [-17] 0x00007ffff79d7694    movl   $0x1, -0x4(%rbp)
+    28: 0x00007ffff79d7694    movl   $0x1, -0x4(%rbp)
   libbar.so`bar() + 1 at bar.cpp:1
-    [-18] 0x00007ffff79d7691    movq   %rsp, %rbp
-    [-19] 0x00007ffff79d7690    pushq  %rbp
+    27: 0x00007ffff79d7691    movq   %rsp, %rbp
+    26: 0x00007ffff79d7690    pushq  %rbp
   libfoo.so`symbol stub for: bar()
-    [-20] 0x00007ffff7bd95d0    jmpq   *0x200a4a(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 32
+    25: 0x00007ffff7bd95d0    jmpq   *0x200a4a(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 32
   libfoo.so`foo() + 8 at foo.cpp:4
-    [-21] 0x00007ffff7bd96e8    callq  0x7ffff7bd95d0            ; symbol stub for: bar()
-    [-22] 0x00007ffff7bd96e4    subq   $0x10, %rsp
+    24: 0x00007ffff7bd96e8    callq  0x7ffff7bd95d0            ; symbol stub for: bar()
+    23: 0x00007ffff7bd96e4    subq   $0x10, %rsp
   libfoo.so`foo() + 1 at foo.cpp:3
-    [-23] 0x00007ffff7bd96e1    movq   %rsp, %rbp
-    [-24] 0x00007ffff7bd96e0    pushq  %rbp
+    22: 0x00007ffff7bd96e1    movq   %rsp, %rbp
+    21: 0x00007ffff7bd96e0    pushq  %rbp
   a.out`symbol stub for: foo()
-    [-25] 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
+    20: 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
   a.out`main + 63 at main.cpp:16
-    [-26] 0x000000000040069f    callq  0x400540                  ; symbol stub for: foo()
+    19: 0x000000000040069f    callq  0x400540                  ; symbol stub for: foo()
   a.out`main + 60 at main.cpp:14
-    [-27] 0x000000000040069c    movl   %ecx, -0xc(%rbp)
-    [-28] 0x000000000040069a    addl   %eax, %ecx
-    [-29] 0x0000000000400697    movl   -0xc(%rbp), %ecx
+    18: 0x000000000040069c    movl   %ecx, -0xc(%rbp)
+    17: 0x000000000040069a    addl   %eax, %ecx
+    16: 0x0000000000400697    movl   -0xc(%rbp), %ecx
   a.out`main + 52 [inlined] inline_function() + 18 at main.cpp:6
-    [-30] 0x0000000000400694    movl   -0x4(%rbp), %eax
+    15: 0x0000000000400694    movl   -0x4(%rbp), %eax
   a.out`main + 49 [inlined] inline_function() + 15 at main.cpp:5
-    [-31] 0x0000000000400691    movl   %eax, -0x4(%rbp)
-    [-32] 0x000000000040068c    addl   $0x1, %eax
-    [-33] 0x0000000000400689    movl   -0x4(%rbp), %eax
+    14: 0x0000000000400691    movl   %eax, -0x4(%rbp)
+    13: 0x000000000040068c    addl   $0x1, %eax
+    12: 0x0000000000400689    movl   -0x4(%rbp), %eax
   a.out`main + 34 [inlined] inline_function() at main.cpp:4
-    [-34] 0x0000000000400682    movl   $0x0, -0x4(%rbp)
+    11: 0x0000000000400682    movl   $0x0, -0x4(%rbp)
   a.out`main + 31 at main.cpp:12
-    [-35] 0x000000000040067f    movl   %eax, -0xc(%rbp)
-    [-36] 0x000000000040067a    addl   $0x1, %eax
-    [-37] 0x0000000000400677    movl   -0xc(%rbp), %eax
+    10: 0x000000000040067f    movl   %eax, -0xc(%rbp)
+    9: 0x000000000040067a    addl   $0x1, %eax
+    8: 0x0000000000400677    movl   -0xc(%rbp), %eax
   a.out`main + 20 at main.cpp:10
-    [-38] 0x0000000000400674    movl   %eax, -0xc(%rbp)
+    7: 0x0000000000400674    movl   %eax, -0xc(%rbp)
     ...missing instructions
-    [-39] 0x00007ffff7df1950    error: no memory mapped at this address
+    6: 0x00007ffff7df1950    error: no memory mapped at this address
   a.out`(none)
-    [-40] 0x0000000000400516    jmpq   *0x200af4(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 16
-    [-41] 0x0000000000400510    pushq  0x200af2(%rip)            ; _GLOBAL_OFFSET_TABLE_ + 8
+    5: 0x0000000000400516    jmpq   *0x200af4(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 16
+    4: 0x0000000000400510    pushq  0x200af2(%rip)            ; _GLOBAL_OFFSET_TABLE_ + 8
   a.out`symbol stub for: foo() + 11
-    [-42] 0x000000000040054b    jmp    0x400510
-    [-43] 0x0000000000400546    pushq  $0x2
-    [-44] 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
+    3: 0x000000000040054b    jmp    0x400510
+    2: 0x0000000000400546    pushq  $0x2
+    1: 0x0000000000400540    jmpq   *0x200ae2(%rip)           ; _GLOBAL_OFFSET_TABLE_ + 40
   a.out`main + 15 at main.cpp:10
-    [-45] 0x000000000040066f    callq  0x400540                  ; symbol stub for: foo()'''])
+    0: 0x000000000040066f    callq  0x400540                  ; symbol stub for: foo()'''])
 
         self.expect("thread trace dump instructions --skip 100 --forwards", inHistory=True,
             substrs=['''thread #1: tid = 815455
     no more data'''])
 
         self.expect("", substrs=['''thread #1: tid = 815455
     no more data'''])

lldb/test/API/commands/trace/TestTraceStartStop.py

def testStartStopLiveThreads(self):
         self.expect("thread trace start", error=True,
             substrs=["error: Thread ", "already traced"])
 
         # We can reconstruct the single instruction executed in the first line
         self.expect("n")
         self.expect("thread trace dump instructions -f",
             patterns=[f'''thread #1: tid = .*
   a.out`main \+ 4 at main.cpp:2
-    \[ 0\] {ADDRESS_REGEX}    movl'''])
+    0: {ADDRESS_REGEX}    movl'''])
 
         # We can reconstruct the instructions up to the second line
         self.expect("n")
         self.expect("thread trace dump instructions -f",
             patterns=[f'''thread #1: tid = .*
   a.out`main \+ 4 at main.cpp:2
-    \[ 0\] {ADDRESS_REGEX}    movl .*
+    0: {ADDRESS_REGEX}    movl .*
   a.out`main \+ 11 at main.cpp:4
-    \[ 1\] {ADDRESS_REGEX}    movl .*
-    \[ 2\] {ADDRESS_REGEX}    jmp  .* ; <\+28> at main.cpp:4
-    \[ 3\] {ADDRESS_REGEX}    cmpl .*
-    \[ 4\] {ADDRESS_REGEX}    jle  .* ; <\+20> at main.cpp:5'''])
+    1: {ADDRESS_REGEX}    movl .*
+    2: {ADDRESS_REGEX}    jmp  .* ; <\+28> at main.cpp:4
+    3: {ADDRESS_REGEX}    cmpl .*
+    4: {ADDRESS_REGEX}    jle  .* ; <\+20> at main.cpp:5'''])
 
         self.expect("thread trace dump instructions",
             patterns=[f'''thread #1: tid = .*
   a.out`main \+ 32 at main.cpp:4
-    \[  0\] {ADDRESS_REGEX}    jle  .* ; <\+20> at main.cpp:5
-    \[ -1\] {ADDRESS_REGEX}    cmpl .*
-    \[ -2\] {ADDRESS_REGEX}    jmp  .* ; <\+28> at main.cpp:4
-    \[ -3\] {ADDRESS_REGEX}    movl .*
+    4: {ADDRESS_REGEX}    jle  .* ; <\+20> at main.cpp:5
+    3: {ADDRESS_REGEX}    cmpl .*
+    2: {ADDRESS_REGEX}    jmp  .* ; <\+28> at main.cpp:4
+    1: {ADDRESS_REGEX}    movl .*
   a.out`main \+ 4 at main.cpp:2
-    \[ -4\] {ADDRESS_REGEX}    movl .* '''])
+    0: {ADDRESS_REGEX}    movl .* '''])
 
         # We stop tracing
         self.expect("thread trace stop")
 
         # We can't stop twice
         self.expect("thread trace stop", error=True,
             substrs=["error: Thread ", "not currently traced"])
 
         # We trace again from scratch, this time letting LLDB to pick the current
         # thread
         self.expect("thread trace start")
         self.expect("n")
         self.expect("thread trace dump instructions -f",
             patterns=[f'''thread #1: tid = .*
   a.out`main \+ 20 at main.cpp:5
-    \[ 0\] {ADDRESS_REGEX}    xorl'''])
+    0: {ADDRESS_REGEX}    xorl'''])
 
         self.expect("thread trace dump instructions",
             patterns=[f'''thread #1: tid = .*
   a.out`main \+ 20 at main.cpp:5
-    \[  0\] {ADDRESS_REGEX}    xorl'''])
+    0: {ADDRESS_REGEX}    xorl'''])
 
         self.expect("c")
         # Now the process has finished, so the commands should fail
         self.expect("thread trace start", error=True,
             substrs=["error: Process must be launched"])
 
         self.expect("thread trace stop", error=True,
             substrs=["error: Process must be launched"])

lldb/test/API/commands/trace/TestTraceTimestampCounters.py

def testTscPerThread(self):
         self.expect("file " + os.path.join(self.getSourceDir(), "intelpt-trace", "a.out"))
         self.expect("b main")
         self.expect("r")
 
         self.traceStartThread(enableTsc=True)
 
         self.expect("n")
         self.expect("thread trace dump instructions --tsc -c 1",
-            patterns=["\[0\] \[tsc=0x[0-9a-fA-F]+\] 0x0000000000400511    movl"])
+            patterns=["0: \[tsc=0x[0-9a-fA-F]+\] 0x0000000000400511    movl"])
 
     @testSBAPIAndCommands
     @skipIf(oslist=no_match(['linux']), archs=no_match(['i386', 'x86_64']))
     def testTscPerProcess(self):
         self.expect("file " + os.path.join(self.getSourceDir(), "intelpt-trace", "a.out"))
         self.expect("b main")
         self.expect("r")
 
         self.traceStartProcess(enableTsc=True)
 
         self.expect("n")
         self.expect("thread trace dump instructions --tsc -c 1",
-            patterns=["\[0\] \[tsc=0x[0-9a-fA-F]+\] 0x0000000000400511    movl"])
+            patterns=["0: \[tsc=0x[0-9a-fA-F]+\] 0x0000000000400511    movl"])
 
     @testSBAPIAndCommands
     @skipIf(oslist=no_match(['linux']), archs=no_match(['i386', 'x86_64']))
     def testDumpingAfterTracingWithoutTsc(self):
         self.expect("file " + os.path.join(self.getSourceDir(), "intelpt-trace", "a.out"))
         self.expect("b main")
         self.expect("r")
 
         self.traceStartThread(enableTsc=False)
 
         self.expect("n")
         self.expect("thread trace dump instructions --tsc -c 1",
-            patterns=["\[0\] \[tsc=unavailable\] 0x0000000000400511    movl"])
+            patterns=["0: \[tsc=unavailable\] 0x0000000000400511    movl"])
 
     @testSBAPIAndCommands
     @skipIf(oslist=no_match(['linux']), archs=no_match(['i386', 'x86_64']))
     def testPSBPeriod(self):
         def isPSBSupported():
             caps_file = "/sys/bus/event_source/devices/intel_pt/caps/psb_cyc"
             if not os.path.exists(caps_file):
                 return False