record-btrace: show trace from enable location

record-btrace: show trace from enable location

The btrace record target shows the branch trace from the location of the first
branch destination.  This is the first BTS records.

After adding incremental updates, we can now add a dummy record for the current
PC when we enable tracing so we show the trace from the location where branch
tracing has been enabled.

2014-01-16  Markus Metzger  <markus.t.metzger@intel.com>

	* btrace.c: Include regcache.h.
	(btrace_add_pc): New.
	(btrace_enable): Call btrace_add_pc.
	(btrace_is_empty): New.
	* btrace.h (btrace_is_empty): New.
	* record-btrace.c (require_btrace, record_btrace_info): Call
	btrace_is_empty.

testsuite/
	* gdb.btrace/Makefile.in (EXECUTABLES): Add delta.
	* gdb.btrace/exception.exp: Update.
	* gdb.btrace/instruction_history.exp: Update.
	* gdb.btrace/record_goto.exp: Update.
	* gdb.btrace/tailcall.exp: Update.
	* gdb.btrace/unknown_functions.exp: Update.
	* gdb.btrace/delta.exp: New.