re PR tree-optimization/69347 (excessive compile time with -O2)

	PR middle-end/69347
	* tree-ssa-threadbackwards.c
	(fsm_find_control_statement_thread_paths): Do not try to lookup
	FSM paths for SSA_NAMEs appearing in abnormal PHIs.

From-SVN: r232593

gcc/ChangeLog

+2016-01-19  Jeff Law  <law@redhat.com>
+
+	PR middle-end/69347
+	* tree-ssa-threadbackwards.c
+	(fsm_find_control_statement_thread_paths): Do not try to lookup
+	FSM paths for SSA_NAMEs appearing in abnormal PHIs.
+
 2016-01-20  Kugan Vivekanandarajah  <kuganv@linaro.org>
 
 	* doc/lto.texi: Remove text that says only Gold has linker plugin

gcc/tree-ssa-threadbackward.c

@@ -99,6 +99,11 @@ fsm_find_control_statement_thread_paths (tree name,
 					 vec<basic_block, va_gc> *&path,
 					 bool seen_loop_phi)
 {
+  /* If NAME appears in an abnormal PHI, then don't try to trace its
+     value back through PHI nodes.  */
+  if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (name))
+    return;
+
   gimple *def_stmt = SSA_NAME_DEF_STMT (name);
   basic_block var_bb = gimple_bb (def_stmt);