re PR debug/46815 (Invalid DW_AT_location for a retval instance of a class that has a virtual function)

	PR debug/46815
	* cp-gimplify.c (cp_genericize): When changing RESULT_DECL
	into invisible reference, change also DECL_VALUE_EXPR of
	NRV optimized variable.

	* g++.dg/guality/pr46815.C: New test.

From-SVN: r167865