re PR debug/88635 (Assembler error when building with "-g -O2 -m32")

re PR debug/88635 (Assembler error when building with "-g -O2 -m32")

	PR debug/88635
	* dwarf2out.c (const_ok_for_output_1): Reject MINUS that contains
	SYMBOL_REF, CODE_LABEL or UNSPEC in subexpressions of second argument.
	Reject PLUS that contains SYMBOL_REF, CODE_LABEL or UNSPEC in
	subexpressions of both operands.
	(mem_loc_descriptor): Handle UNSPEC if target hook acks it and all the
	subrtxes are CONSTANT_P.
	* config/i386/i386.c (ix86_const_not_ok_for_debug_p): Revert
	2018-11-09 changes.

	* gcc.dg/debug/dwarf2/pr88635.c: New test.

From-SVN: r267594