perf auxtrace: Add an option to synthesize callchains for regular events

Currently, callchains can be synthesized only for synthesized events. Add
an itrace option to synthesize callchains for regular events.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200401101613.6201-9-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/Documentation/itrace.txt b/tools/perf/Documentation/itrace.txt
index 82ff7da..671e154 100644
--- a/tools/perf/Documentation/itrace.txt
+++ b/tools/perf/Documentation/itrace.txt
@@ -10,6 +10,7 @@
 		e	synthesize error events
 		d	create a debug log
 		g	synthesize a call chain (use with i or x)
+		G	synthesize a call chain on existing event records
 		l	synthesize last branch entries (use with i or x)
 		s       skip initial number of events