PR debug/49382

	PR debug/49382
	* dwarf2out.c (dw_loc_list_node): Add force field.
	(add_var_loc_to_decl): For PARM_DECL, attempt to keep
	the incoming location in the list, even if it is modified
	before first real insn.
	(output_loc_list): Emit empty ranges with force flag set.
	(dw_loc_list): If first range of a PARM_DECL is empty,
	set force flag.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@175076 138bc75d-0d04-0410-961f-82ee72b054a4