PR debug/48203

	PR debug/48203
	* cfgexpand.c (expand_debug_expr) <case SSA_NAME>: Only
	create ENTRY_VALUE if incoming or address of incoming's MEM
	is a hard REG.
	* dwarf2out.c (mem_loc_descriptor): Don't emit
	DW_OP_GNU_entry_value of DW_OP_fbreg.
	* var-tracking.c (vt_add_function_parameter): Ensure cselib_lookup
	on ENTRY_VALUE is able to find the canonical parameter VALUE.
	* cselib.c (rtx_equal_for_cselib_1) <case ENTRY_VALUE>: Use
	rtx_equal_p instead of rtx_equal_for_cselib_1 to compare
	ENTRY_VALUE_EXPs.
	(cselib_hash_rtx) <case ENTRY_VALUE>: If ENTRY_VALUE_EXP
	is a REG_P or MEM_P with REG_P address, compute hash directly
	instead of calling cselib_hash_rtx on ENTRY_VALUE_EXP.
	(preserve_only_constants): Don't clear VALUES forwaring
	ENTRY_VALUE to some other VALUE.

	* gcc.dg/pr48203.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@171640 138bc75d-0d04-0410-961f-82ee72b054a4