Allow 2 insns from sched group to issue in same cycle, if no stalls needed.

	gcc/
	PR rtl-optimization/81434
	* haifa-sched.c (prune_ready_list): Init min_cost_group to 0.  Update
	comment for main loop.  In sched_group_found if, also add checks for
	pass and min_cost_group.

From-SVN: r253628

gcc/ChangeLog

+2017-10-10  Jim Wilson  <wilson@tuliptree.org>
+
+	PR rtl-optimization/81434
+	* haifa-sched.c (prune_ready_list): Init min_cost_group to 0.  Update
+	comment for main loop.  In sched_group_found if, also add checks for
+	pass and min_cost_group.
+
 2017-10-10  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000.c (TARGET_INSN_COST): New.

gcc/haifa-sched.c

@@ -6303,7 +6303,7 @@ prune_ready_list (state_t temp_state, bool first_cycle_insn_p,
 {
   int i, pass;
   bool sched_group_found = false;
-  int min_cost_group = 1;
+  int min_cost_group = 0;
 
   if (sched_fusion)
     return;
@@ -6319,8 +6319,8 @@ prune_ready_list (state_t temp_state, bool first_cycle_insn_p,
     }
 
   /* Make two passes if there's a SCHED_GROUP_P insn; make sure to handle
-     such an insn first and note its cost, then schedule all other insns
-     for one cycle later.  */
+     such an insn first and note its cost.  If at least one SCHED_GROUP_P insn
+     gets queued, then all other insns get queued for one cycle later.  */
   for (pass = sched_group_found ? 0 : 1; pass < 2; )
     {
       int n = ready.n_ready;
@@ -6333,7 +6333,8 @@ prune_ready_list (state_t temp_state, bool first_cycle_insn_p,
 	  if (DEBUG_INSN_P (insn))
 	    continue;
 
-	  if (sched_group_found && !SCHED_GROUP_P (insn))
+	  if (sched_group_found && !SCHED_GROUP_P (insn)
+	      && ((pass == 0) || (min_cost_group >= 1)))
 	    {
 	      if (pass == 0)
 		continue;