re PR tree-optimization/87776 (Compile time hog during RPO VN)

2018-11-02  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87776
	* tree-ssa-sccvn.c (do_rpo_vn): Do not mark backedges
	executable when iterating but running into rpo-vn-max-loop-depth
	and not eliding the iteration.

	* gcc.dg/torture/pr87776.c: New testcase.

From-SVN: r265739

gcc/ChangeLog

+2018-11-02  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87776
+	* tree-ssa-sccvn.c (do_rpo_vn): Do not mark backedges
+	executable when iterating but running into rpo-vn-max-loop-depth
+	and not eliding the iteration.
+
 2018-11-30  Jan Hubicka  <jh@suse.cz>
 
 	* tree.c (free_lang_data_in_decl): Free TREE_TYPE and alignment of

gcc/testsuite/ChangeLog

+2018-11-02  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/87776
+	* gcc.dg/torture/pr87776.c: New testcase.
+
 2018-11-01  Marek Polacek  <polacek@redhat.com>
 
 	Implement P0846R0, ADL and function templates.

gcc/testsuite/gcc.dg/torture/pr87776.c

+/* { dg-do compile } */
+/* { dg-additional-options "--param rpo-vn-max-loop-depth=2" } */
+
+int wp;
+
+void
+ff (void)
+{
+  int *s3 = ℘
+
+  for (wp = 0; wp < 1; ++wp)
+    {
+      if (wp != 0)
+	{
+o8:
+	  ;
+	}
+      else
+	{
+b7:
+	  while (wp < 1)
+	    {
+	    }
+	}
+
+      for (*s3 = 0; *s3 < 1; ++*s3)
+	{
+	  for (wp = 0; wp < 1; ++wp)
+	    for (wp = 0; wp < 1; ++wp)
+	      {
+	      }
+
+	  for (wp = 0; wp < 1; ++wp)
+	    goto o8;
+
+	  for (wp = 0; wp < 1; ++wp)
+	    goto b7;
+	}
+    }
+}

gcc/tree-ssa-sccvn.c

@@ -6449,7 +6449,6 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
 	      FOR_EACH_EDGE (e, ei, header->preds)
 		if (e->flags & EDGE_DFS_BACK)
 		  {
-		    e->flags |= EDGE_EXECUTABLE;
 		    /* There can be a non-latch backedge into the header
 		       which is part of an outer irreducible region.  We
 		       cannot avoid iterating this block then.  */
@@ -6462,6 +6461,8 @@ do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
 				   e->src->index, e->dest->index, loop->num);
 			non_latch_backedge = true;
 		      }
+		    else
+		      e->flags |= EDGE_EXECUTABLE;
 		  }
 	      rpo_state[bb_to_rpo[header->index]].iterate = non_latch_backedge;
 	    }