* lcm.c (optimize_mode_switching): Do not rebuild liveness information

	* lcm.c (optimize_mode_switching):  Do not rebuild liveness information
	when no changes has been made.

	* gcse.c (reg_set_bitmap): Turn into reg_set.
	(modify_mem_list_set, canon_modify_mem_list_set)
	(clear_modify_mem_tables, free_modify_mem_tables): New.
	(gcse_main); Use free_modify_mem_tables.
	(free_gcse_mem): Likewise; free the bitmaps.
	(alloc_gcse_main): Initialize the bitmaps.
	(canon_list_insert): Set canon_modify_mem_list_set.
	(record_last_mem_set_info): Likewise; set modify_mem_list_set.
	(compute_hash_table): Use clear_modify_mem_tables.
	(reset_opr_set_tables): Likewise.
	(oprs_not_set_p): reg_set_bitmap is regset.
	(mark_set, mark_clobber): Likewise.

	* df.h (DF_EQUIV_NOTES): New constant.
	(df_insn_refs_record): Record uses inside or REG_EQUIV/EQUAL notes
	when asked for.

	* sched-rgn.c (CHECK_DEAD_NOTES): New constant.
	(init_regions, schedule_insns): Conditionalize the checking
	code by CHECK_DEAD_NOTES; avoid multiple calls to update_life_info.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@46634 138bc75d-0d04-0410-961f-82ee72b054a4