tree-loop-distribution.c (generate_loops_for_partition): Remove inner loop's…

tree-loop-distribution.c (generate_loops_for_partition): Remove inner loop's exit stmt by making it always exit the loop...

	* tree-loop-distribution.c (generate_loops_for_partition): Remove
	inner loop's exit stmt by making it always exit the loop, otherwise
	we would generate an infinite empty loop.

	gcc/testsuite
	* gcc.dg/tree-ssa/ldist-27.c: New test.

From-SVN: r253580

gcc/ChangeLog

 2017-10-10  Bin Cheng  <bin.cheng@arm.com>
 
+	* tree-loop-distribution.c (generate_loops_for_partition): Remove
+	inner loop's exit stmt by making it always exit the loop, otherwise
+	we would generate an infinite empty loop.
+
+2017-10-10  Bin Cheng  <bin.cheng@arm.com>
+
 	* tree-vect-loop-manip.c (slpeel_tree_duplicate_loop_to_edge_cfg): Skip
 	renaming variables in new preheader if it's deleted.
 

gcc/testsuite/ChangeLog

+2017-10-10  Bin Cheng  <bin.cheng@arm.com>
+
+	* gcc.dg/tree-ssa/ldist-27.c: New test.
+
 2017-10-09  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	* gcc.target/powerpc/amo1.c: New test.

gcc/testsuite/gcc.dg/tree-ssa/ldist-27.c

+/* { dg-do run } */
+/* { dg-options "-O3 -ftree-loop-distribute-patterns -fdump-tree-ldist-details" } */
+
+#define M (300)
+#define N (200)
+
+struct st
+{
+  double a[M];
+  double b[M];
+  double c[M][N];
+};
+
+int __attribute__ ((noinline)) foo (struct st *s)
+{
+  int i, j;
+  for (i = 0; i != M;)
+    {
+      s->a[i] = 0.0;
+      s->b[i] = 1.0;
+      for (j = 0; 1; ++j)
+	{
+	  if (j == N) goto L2;
+	  s->c[i][j] = 0.0;
+	}
+L2:
+      ++i;
+    }
+  return 0;
+}
+
+int main (void)
+{
+  struct st s;
+  return foo (&s);
+}
+
+/* { dg-final { scan-tree-dump "distributed: split to " "ldist" } } */

gcc/tree-loop-distribution.c

@@ -830,6 +830,10 @@ generate_loops_for_partition (struct loop *loop, partition *partition,
   for (i = 0; i < loop->num_nodes; i++)
     {
       basic_block bb = bbs[i];
+      edge inner_exit = NULL;
+
+      if (loop != bb->loop_father)
+	inner_exit = single_exit (bb->loop_father);
 
       for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);)
 	{
@@ -848,11 +852,17 @@ generate_loops_for_partition (struct loop *loop, partition *partition,
 	      && !is_gimple_debug (stmt)
 	      && !bitmap_bit_p (partition->stmts, gimple_uid (stmt)))
 	    {
-	      /* Choose an arbitrary path through the empty CFG part
-		 that this unnecessary control stmt controls.  */
+	      /* In distribution of loop nest, if bb is inner loop's exit_bb,
+		 we choose its exit edge/path in order to avoid generating
+		 infinite loop.  For all other cases, we choose an arbitrary
+		 path through the empty CFG part that this unnecessary
+		 control stmt controls.  */
 	      if (gcond *cond_stmt = dyn_cast <gcond *> (stmt))
 		{
-		  gimple_cond_make_false (cond_stmt);
+		  if (inner_exit && inner_exit->flags & EDGE_TRUE_VALUE)
+		    gimple_cond_make_true (cond_stmt);
+		  else
+		    gimple_cond_make_false (cond_stmt);
 		  update_stmt (stmt);
 		}
 	      else if (gimple_code (stmt) == GIMPLE_SWITCH)