[llvm] [llvm]Add a simple Telemetry framework (PR #102323)

[Vy Nguyen via llvm-commits]

================
@@ -23,82 +67,94 @@
 namespace llvm {
 namespace telemetry {
 
-using SteadyTimePoint = std::chrono::time_point<std::chrono::steady_clock>;
-
 struct TelemetryConfig {
   // If true, telemetry will be enabled.
-  bool enable_telemetry;
-
-  // Additional destinations to send the logged entries.
-  // Could be stdout, stderr, or some local paths.
-  // Note: these are destinations are __in addition to__ whatever the default
-  // destination(s) are, as implemented by vendors.
-  std::vector<std::string> additional_destinations;
+  bool EnableTelemetry;
+
+  // Implementation-defined names of additional destinations to send
+  // telemetry data (Could be stdout, stderr, or some local paths, etc).
+  //
+  // These strings will be interpreted by the vendor's code.
+  // So the users must pick the  from their vendor's pre-defined
+  // set of Destinations.
+  std::vector<std::string> AdditionalDestinations;
 };
 
+using SteadyTimePoint = std::chrono::time_point<std::chrono::steady_clock>;
+
 struct TelemetryEventStats {
-  // REQUIRED: Start time of event
-  SteadyTimePoint m_start;
-  // OPTIONAL: End time of event - may be empty if not meaningful.
-  std::optional<SteadyTimePoint> m_end;
+  // REQUIRED: Start time of an event
+  SteadyTimePoint Start;
+  // OPTIONAL: End time of an event - may be empty if not meaningful.
+  std::optional<SteadyTimePoint> End;
   // TBD: could add some memory stats here too?
 
   TelemetryEventStats() = default;
-  TelemetryEventStats(SteadyTimePoint start) : m_start(start) {}
-  TelemetryEventStats(SteadyTimePoint start, SteadyTimePoint end)
-      : m_start(start), m_end(end) {}
-
-  std::string ToString() const;
+  TelemetryEventStats(SteadyTimePoint Start) : Start(Start) {}
+  TelemetryEventStats(SteadyTimePoint Start, SteadyTimePoint End)
+      : Start(Start), End(End) {}
 };
 
 struct ExitDescription {
-  int exit_code;
-  std::string description;
+  int ExitCode;
+  std::string Description;
+};
 
-  std::string ToString() const;
+// For isa, dyn_cast, etc operations on TelemetryInfo.
+typedef unsigned KindType;
+struct EntryKind {
+  static const KindType Base = 0;
 };
----------------
oontvoo wrote:

The common LLVM code in this directory likely does not use dyn_cast (since it's mostly abstract API), but subclass(es), both in upstream tools (ie., LLDB which chooses to extend this Telemetry library) and downstream in vendor specific code, will need it.

So it's more convenient to have the `getKind()` defined in the base API 

https://github.com/llvm/llvm-project/pull/102323