tree-ssa-threadbackward.c (fsm_find_thread_path): Make GC vectors heap vectors.

	* tree-ssa-threadbackward.c (fsm_find_thread_path): Make GC
	vectors heap vectors.  Clean up comments.
	Make visited_bbs a reference.
	(profitable_jump_thread_path): Make GC
	vectors heap vectors.  Clean up comments.
	Misc cleanups.
	(convert_and_register_jump_thread_path): Make GC vectors heap
	vectors.
	(check_subpath_and_update_thread_path): Same.  Clean up comments.
	Make visited_bbs a reference.
	(handle_phi): Abstract common code to to
	register_jump_thread_path_if_profitable.
	Rename VAR_BB to DEF_BB.
	Update comments.
	Make GC vectors heap vectors.
	Make visited_bbs a reference.
	(handle_assignment): Same.
	(register_jump_thread_path_if_profitable): New.
	(fsm_find_control_statement_thread_paths): Rename VAR_BB to
	DEF_BB.
	Make GC	vectors heap vectors.  Clean up comments.
	Make visited_bbs a reference.
	(find_jump_threads_backwards): Make visited_bbs live in the stack.
	* tree-ssa-threadupdate.c (delete_jump_thread_path): Fix typo in
	comment.

From-SVN: r251998

gcc/ChangeLog

+2017-09-12  Aldy Hernandez  <aldyh@redhat.com>
+
+	* tree-ssa-threadbackward.c (fsm_find_thread_path): Make GC
+	vectors heap vectors.  Clean up comments.
+	Make visited_bbs a reference.
+	(profitable_jump_thread_path): Make GC
+	vectors heap vectors.  Clean up comments.
+	Misc cleanups.
+	(convert_and_register_jump_thread_path): Make GC vectors heap
+	vectors.
+	(check_subpath_and_update_thread_path): Same.  Clean up comments.
+	Make visited_bbs a reference.
+	(handle_phi): Abstract common code to to
+	register_jump_thread_path_if_profitable.
+	Rename VAR_BB to DEF_BB.
+	Update comments.
+	Make GC vectors heap vectors.
+	Make visited_bbs a reference.
+	(handle_assignment): Same.
+	(register_jump_thread_path_if_profitable): New.
+	(fsm_find_control_statement_thread_paths): Rename VAR_BB to
+	DEF_BB.
+	Make GC	vectors heap vectors.  Clean up comments.
+	Make visited_bbs a reference.
+	(find_jump_threads_backwards): Make visited_bbs live in the stack.
+	* tree-ssa-threadupdate.c (delete_jump_thread_path): Fix typo in
+	comment.
+
 2017-09-11  Max Filippov  <jcmvbkbc@gmail.com>
 
 	PR target/82181

gcc/tree-ssa-threadupdate.c

@@ -2577,7 +2577,7 @@ thread_through_all_blocks (bool may_peel_loop_headers)
   return retval;
 }
 
-/* Delete the jump threading path PATH.  We have to explcitly delete
+/* Delete the jump threading path PATH.  We have to explicitly delete
    each entry in the vector, then the container.  */
 
 void