g++.dg/bprob* is failing currently with autofdo.

Running in gdb shows that there is a very deep recursion in get_index_by_decl until it
overflows the stack.

gcc/:
2017-12-11  Andi Kleen  <ak@linux.intel.com>

	PR gcov-profile/83355
	* auto-profile.c (string_table::get_index_by_decl): Don't
	recurse when abstract origin points to itself.

From-SVN: r255540