re PR middle-end/37243 (IRA causes wrong code generation)

re PR middle-end/37243 (IRA causes wrong code generation)

gcc/
	PR middle-end/37243
	* ira-build.c (form_loop_tree): Reverse BB walk.
	(create_bb_allocnos): Likewise.
	* ira-lives.c (make_regno_born_and_dead, regs_set): Delete.
	(mark_reg_store): Rename to...
	(mark_ref_live): ...this and take a df_ref argument instead of
	note_stores arguments.  Assert that we have a register.
	(mark_reg_clobber): Delete.
	(def_conflicts_with_inputs_p): New function.
	(mark_reg_conflicts): Delete.
	(mark_reg_death): Rename to...
	(mark_ref_dead): ...this and take a df_ref argument instead of
	a register.  Assert that we have a register.
	(process_bb_node_lives): Hoist frequency calculation out of
	instruction walk.  Convert from a forwards scan to a backwards scan.
	Use DF_REF_USES and DF_REF_DEFS instead of register notes and
	note_stores.  Remove EH_RETURN_DATA_REGNO and regs_set handling.
	(create_allocno_live_ranges): Don't create regs_set.

From-SVN: r139993