re PR tree-optimization/49073 (g++ optimizer breaks do-while code)

	PR tree-optimization/49073
	* gimple-fold.c (and_comparisons_1, or_comparisons_1): Return
	NULL if PHI argument is SSA_NAME, whose def_stmt is dominated
	by the PHI.
	* tree-ssa-ifcombine.c (tree_ssa_ifcombine): Calculate dominators.

	* gcc.c-torture/execute/pr49073.c: New test.

From-SVN: r173948

gcc/ChangeLog

+2011-05-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/49073
+	* gimple-fold.c (and_comparisons_1, or_comparisons_1): Return
+	NULL if PHI argument is SSA_NAME, whose def_stmt is dominated
+	by the PHI.
+	* tree-ssa-ifcombine.c (tree_ssa_ifcombine): Calculate dominators.
+
 2011-05-20  Richard Guenther  <rguenther@suse.de>
 
 	PR middle-end/48849

gcc/gimple-fold.c

 /* Statement simplification on GIMPLE.
-   Copyright (C) 2010 Free Software Foundation, Inc.
+   Copyright (C) 2010, 2011 Free Software Foundation, Inc.
    Split out from tree-ssa-ccp.c.
 
 This file is part of GCC.
@@ -2278,8 +2278,19 @@ and_comparisons_1 (enum tree_code code1, tree op1a, tree op1b,
 		    }
 		  else if (TREE_CODE (arg) == SSA_NAME)
 		    {
-		      tree temp = and_var_with_comparison (arg, invert,
-							   code2, op2a, op2b);
+		      tree temp;
+		      gimple def_stmt = SSA_NAME_DEF_STMT (arg);
+		      /* In simple cases we can look through PHI nodes,
+			 but we have to be careful with loops.
+			 See PR49073.  */
+		      if (! dom_info_available_p (CDI_DOMINATORS)
+			  || gimple_bb (def_stmt) == gimple_bb (stmt)
+			  || dominated_by_p (CDI_DOMINATORS,
+					     gimple_bb (def_stmt),
+					     gimple_bb (stmt)))
+			return NULL_TREE;
+		      temp = and_var_with_comparison (arg, invert, code2,
+						      op2a, op2b);
 		      if (!temp)
 			return NULL_TREE;
 		      else if (!result)
@@ -2728,8 +2739,19 @@ or_comparisons_1 (enum tree_code code1, tree op1a, tree op1b,
 		    }
 		  else if (TREE_CODE (arg) == SSA_NAME)
 		    {
-		      tree temp = or_var_with_comparison (arg, invert,
-							  code2, op2a, op2b);
+		      tree temp;
+		      gimple def_stmt = SSA_NAME_DEF_STMT (arg);
+		      /* In simple cases we can look through PHI nodes,
+			 but we have to be careful with loops.
+			 See PR49073.  */
+		      if (! dom_info_available_p (CDI_DOMINATORS)
+			  || gimple_bb (def_stmt) == gimple_bb (stmt)
+			  || dominated_by_p (CDI_DOMINATORS,
+					     gimple_bb (def_stmt),
+					     gimple_bb (stmt)))
+			return NULL_TREE;
+		      temp = or_var_with_comparison (arg, invert, code2,
+						     op2a, op2b);
 		      if (!temp)
 			return NULL_TREE;
 		      else if (!result)

gcc/testsuite/ChangeLog

+2011-05-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/49073
+	* gcc.c-torture/execute/pr49073.c: New test.
+
 2011-06-19  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/18918

gcc/testsuite/gcc.c-torture/execute/pr49073.c

+/* PR tree-optimization/49073 */
+
+extern void abort (void);
+int a[] = { 1, 2, 3, 4, 5, 6, 7 }, c;
+
+int
+main ()
+{
+  int d = 1, i = 1;
+  _Bool f = 0;
+  do
+    {
+      d = a[i];
+      if (f && d == 4)
+	{
+	  ++c;
+	  break;
+	}
+      i++;
+      f = (d == 3);
+    }
+  while (d < 7);
+  if (c != 1)
+    abort ();
+  return 0;
+}

gcc/tree-ssa-ifcombine.c

 /* Combining of if-expressions on trees.
-   Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
    Contributed by Richard Guenther <rguenther@suse.de>
 
 This file is part of GCC.
@@ -625,6 +625,7 @@ tree_ssa_ifcombine (void)
   int i;
 
   bbs = blocks_in_phiopt_order ();
+  calculate_dominance_info (CDI_DOMINATORS);
 
   for (i = 0; i < n_basic_blocks - NUM_FIXED_BLOCKS; ++i)
     {