[reporting][perf] report InferPrint time taken

Summary:
- InferPrint reports time stats only, logged in `reporting_stats/` as well as a `PerformanceStats` event with `stats_type: reporting`
- Perf reporting can now be registered at one point (with desired start real and cpu times) and triggered later

Reviewed By: dulmarod

Differential Revision: D7332435

fbshipit-source-id: 2e17c7f

infer/src/backend/InferPrint.ml

@@ -866,11 +866,6 @@ let get_summary_iterator () =
   iterate
 
 
-let register_perf_stats_report () =
-  let filename = F.sprintf "%s.json" Config.perf_stats_prefix in
-  PerfStats.register_report_at_exit filename PerfStats.Reporting
-
-
 (** Although the out_file is an Option type, the None option is strictly meant for the
   logs format_kind, and all other formats should contain an outfile value. *)
 let mk_format format_kind fname =
@@ -969,6 +964,17 @@ let pp_summary_and_issues formats_by_report_kind issue_formats =
   finalize_and_close_files formats_by_report_kind stats
 
 
+let register_perf_stats_report () =
+  let fname = F.sprintf "%s.json" Config.perf_stats_prefix in
+  let rtime_span, initial_times = (Mtime_clock.counter (), Unix.times ()) in
+  PerfStats.register_report (PerfStats.Time (rtime_span, initial_times)) fname PerfStats.Reporting
+
+
+let report_perf_stats () =
+  let fname = F.sprintf "%s.json" Config.perf_stats_prefix in
+  PerfStats.get_reporter fname PerfStats.Reporting ()
+
+
 let main ~report_json =
   let issue_formats = init_issues_format_list report_json in
   let formats_by_report_kind =
@@ -979,8 +985,9 @@ let main ~report_json =
   in
   register_perf_stats_report () ;
   init_files formats_by_report_kind ;
-  match Config.from_json_report with
+  ( match Config.from_json_report with
   | Some fname ->
       pp_json_report_by_report_kind formats_by_report_kind fname
   | None ->
-      pp_summary_and_issues formats_by_report_kind issue_formats
+      pp_summary_and_issues formats_by_report_kind issue_formats ) ;
+  report_perf_stats ()