re PR middle-end/38586 (quadratic behaviour in find_temp_slot_from_address.)

	PR middle-end/38586
	* function.c (struct temp_slot): Move to the section of the file
	that deals with temp slots.  Remove field 'address'.
	(temp_slot_address_table): New hash table of address -> temp slot.
	(struct temp_slot_address_entry): New struct, items for the table.
	(temp_slot_address_compute_hash, temp_slot_address_hash,
	temp_slot_address_eq, insert_temp_slot_address): Support functions
	for the new table.
	(find_temp_slot_from_address): Rewrite to use the new hash table.
	(remove_unused_temp_slot_addresses): Remove addresses of temp
	slots that have been made available.
	(remove_unused_temp_slot_addresses_1): Call-back for htab_traverse,
	worker function for remove_unused_temp_slot_addresses.
	(assign_stack_temp_for_type): Don't clear the temp slot address list.
	Add the temp slot address to the address -> temp slot map.
	(update_temp_slot_address): Update via insert_temp_slot_address.
	(free_temp_slots): Call remove_unused_temp_slot_addresses.
	(pop_temp_slots): Likewise.
	(init_temp_slots): Allocate the address -> temp slot map, or empty
	the map if it is already allocated.
	(prepare_function_start): Initialize temp slot processing.

From-SVN: r143041