Simplify CFG copying tables

Simplify CFG copying tables

This simplifies the maps between original and new basic blocks and
loops as used for CFG copying.  Instead of using a pointer hash
table to allocated mapping entries use a hash_map with int_hash,
removing the indirection and code duplication.  We can use -1 and
-2 as empty/deleted values as those are not valid basic-block
indices or loop numbers.

2020-10-21  Richard Biener  <rguenther@suse.de>

	* cfg.c (htab_bb_copy_original_entry): Remove.
	(bb_copy_hasher): Likewise.
	(bb_original, bb_copy, loop_copy): Use
	hash_map<int_hash<int, -1, -2>, int>.
	(original_copy_bb_pool): Remove.
	(initialize_original_copy_tables): Adjust.
	(reset_original_copy_tables): Likewise.
	(free_original_copy_tables): Likewise.
	(original_copy_tables_initialized_p): Likewise.
	(copy_original_table_clear): Simplify.
	(copy_original_table_set): Likewise.
	(get_bb_original): Likewise.
	(get_bb_copy): Likewise.
	(get_loop_copy): Likewise.