except.h (eh_nesting_info): Add new structure defintion.

except.h (eh_nesting_info): Add new structure defintion.

Tue Aug 10 10:47:42 EDT 1999  Andrew MacLeod  <amacleod@cygnus.com>

	* except.h (eh_nesting_info): Add new structure defintion.
	(init_eh_nesting_info, free_eh_nesting_info): Add function prototypes.
	(reachable_handlers, update_rethrow_references): Add function
	prototypes.
	* rtl.h (struct rtvec_def): Update comments.  REG_EH_RETHROW takes
	a rethrow symbol instead of an integer exception region number.
	* flow.c (Make_edges): Use new exception nesting routines to determine
	which handlers are reachable from a CALL or asynchronous insn.
	Dont add an edge for calls with a REG_EH_REGION of -1 to non-local
	goto receivers.
	(delete_eh_regions): Update rethrow labels, and don't delete
	regions which are the target of a rethrow.
	* except.c (struct func_eh_entry): Add rethrow_ref field, now we can
	avoid overloading the SYMBOL_REF_USED flag.
	(rethrow_symbol_map): Use new rethrow_ref field.
	(rethrow_used): Use new rethrow_ref field.
	(expand_rethrow): REG_EH_RETHROW now has a SYMBOL_REF instead
	of an integer.  Fix formatting.
	(output_exception_table_entry): Use new rethrow_ref field.
	(can_throw): Check for EH_REGION_NOTE before deciding
	whether a CALL can throw or not.
	(scan_region): Call rethrow_used() instead of accessing data structure.
	(update_rethrow_references): New function to make sure only regions
	which are still targets of a rethrow are flagged as such.
	(process_nestinfo): New static function to initialize a handler
	list for a specific region.
	(init_eh_nesting_info): New function to allocate and initialize
	the list of all EH handlers reachable from all regions.
	(reachable_handlers): New function to retrieve the list of handlers
	reachable from a specific region and insn.
	(free_eh_nesting_info): New function to dispose of a list of
	reachable handlers.

From-SVN: r28647