re PR tree-optimization/57685 (GCC stuck in an infinite loop)

2013-08-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/57685
	* tree-vrp.c (register_edge_assert_for_1): Recurse only for
	single-use operands to avoid exponential complexity.

	* gcc.dg/torture/pr57685.c: New testcase.

From-SVN: r202068

gcc/ChangeLog

+2013-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/57685
+	* tree-vrp.c (register_edge_assert_for_1): Recurse only for
+	single-use operands to avoid exponential complexity.
+
 2013-08-28  Dehao Chen  <dehao@google.com>
 
 	* ipa-inline.c (edge_badness): Fix integer underflow.

gcc/testsuite/ChangeLog

+2013-08-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/57685
+	* gcc.dg/torture/pr57685.c: New testcase.
+
 2013-08-28  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/58255

gcc/testsuite/gcc.dg/torture/pr57685.c

+/* { dg-do compile } */
+
+unsigned f(void)
+{
+  unsigned a;
+  int b, c, d, e;
+
+  for(c = 27; c < 40; c++)
+    b |= d |= b;
+
+  if(b)
+    a = e;
+
+  return a;
+}

gcc/tree-vrp.c

@@ -5410,10 +5410,14 @@ register_edge_assert_for_1 (tree op, enum tree_code code,
 	       && gimple_assign_rhs_code (op_def) == BIT_IOR_EXPR))
     {
       /* Recurse on each operand.  */
-      retval |= register_edge_assert_for_1 (gimple_assign_rhs1 (op_def),
-					    code, e, bsi);
-      retval |= register_edge_assert_for_1 (gimple_assign_rhs2 (op_def),
-					    code, e, bsi);
+      tree op0 = gimple_assign_rhs1 (op_def);
+      tree op1 = gimple_assign_rhs2 (op_def);
+      if (TREE_CODE (op0) == SSA_NAME
+	  && has_single_use (op0))
+	retval |= register_edge_assert_for_1 (op0, code, e, bsi);
+      if (TREE_CODE (op1) == SSA_NAME
+	  && has_single_use (op1))
+	retval |= register_edge_assert_for_1 (op1, code, e, bsi);
     }
   else if (gimple_assign_rhs_code (op_def) == BIT_NOT_EXPR
 	   && TYPE_PRECISION (TREE_TYPE (gimple_assign_lhs (op_def))) == 1)