record-btrace: extend unwinder

Extend the always failing unwinder to provide the PC based on the call
structure detected in the branch trace.

The unwinder supports normal frames and tailcall frames.
Inline frames are not supported.

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

	* record.h (record_btrace_frame_unwind)
	(record_btrace_tailcall_frame_unwind): New declarations.
	* dwarf2-frame: Include record.h
	(dwarf2_frame_cfa): Throw an error for btrace frames.
	* record-btrace.c: Include hashtab.h.
	(btrace_get_bfun_name): New.
	(btrace_call_history): Call btrace_get_bfun_name.
	(struct btrace_frame_cache): New.
	(bfcache): New.
	(bfcache_hash, bfcache_eq, bfcache_new): New.
	(btrace_get_frame_function): New.
	(record_btrace_frame_unwind_stop_reason): Allow unwinding.
	(record_btrace_frame_this_id): Compute own id.
	(record_btrace_frame_prev_register): Provide PC, throw_error
	for all other registers.
	(record_btrace_frame_sniffer): Detect btrace frames.
	(record_btrace_tailcall_frame_sniffer): New.
	(record_btrace_frame_dealloc_cache): New.
	(record_btrace_frame_unwind): Add new functions.
	(record_btrace_tailcall_frame_unwind): New.
	(_initialize_record_btrace): Allocate cache.
	* btrace.c (btrace_clear): Call reinit_frame_cache.
	* NEWS: Announce it.

testsuite/
	* gdb.btrace/record_goto.exp: Add backtrace test.
	* gdb.btrace/tailcall.exp: Add backtrace test.

1 files changed, 2 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index c6402fe..6b7f4a4 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -19,6 +19,8 @@
   'record instruction-history' commands are now inclusive.
 
 * The btrace record target now supports the 'record goto' command.
+  For locations inside the execution trace, the back trace is computed
+  based on the information stored in the execution trace.
 
 *** Changes in GDB 7.7