re PR testsuite/68580 (FAIL: c-c++-common/tsan/pr65400-1.c -O0 execution test)

	PR tree-optimization/68580
	* params.def (FSM_MAXIMUM_PHI_ARGUMENTS): New param.
	* tree-ssa-threadbackward.c
	(fsm_find_control_statement_thread_paths): Do not try to walk
	through large PHI nodes.

From-SVN: r233053

gcc/ChangeLog

+2016-02-01  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/68580
+	* params.def (FSM_MAXIMUM_PHI_ARGUMENTS): New param.
+	* tree-ssa-threadbackward.c
+	(fsm_find_control_statement_thread_paths): Do not try to walk
+	through large PHI nodes.
+
 2016-02-01  Jakub Jelinek  <jakub@redhat.com>
 
 	* ifcvt.c (bb_ok_for_noce_convert_multiple_sets): Return false

gcc/params.def

@@ -1150,6 +1150,11 @@ DEFPARAM (PARAM_FSM_SCALE_PATH_STMTS,
 	  "Scale factor to apply to the number of statements in a threading path when comparing to the number of (scaled) blocks.",
 	  2, 1, 10)
 
+DEFPARAM (PARAM_FSM_MAXIMUM_PHI_ARGUMENTS,
+	  "fsm-maximum-phi-arguments",
+	  "Maximum number of arguments a PHI may have before the FSM threader will not try to thread through its block.",
+	  100, 1, 999999)
+
 DEFPARAM (PARAM_FSM_SCALE_PATH_BLOCKS,
 	  "fsm-scale-path-blocks",
 	  "Scale factor to apply to the number of blocks in a threading path when comparing to the number of (scaled) statements.",