PR debug/37738
	* dwarf2out.c (common_block_die_table): New variable.
	(common_block_die_table_hash, common_block_die_table_eq): New
	functions.
	(gen_variable_die): Look up a DW_TAG_common_block die for a particular
	COMMON block in the current scope rather than globally.  Optimize
	DW_OP_addr SYMBOL_REF DW_OP_plus_uconst off into
	DW_OP_addr SYMBOL_REF+off.

	* gfortran.dg/debug/pr37738.f: New test.

From-SVN: r140944