re PR tree-optimization/35231 (VRP miscompiles libX11)

2008-02-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/35231
	* tree-vrp.c (register_edge_assert_for): Do not assume A == 0
	if A | B != 1.

	* gcc.c-torture/execute/pr35231.c: New testcase.

From-SVN: r132378

gcc/ChangeLog

+2008-02-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/35231
+	* tree-vrp.c (register_edge_assert_for): Do not assume A == 0
+	if A | B != 1.
+
 2008-02-17  Uros Bizjak  <ubizjak@gmail.com>
 
 	Revert:

gcc/testsuite/ChangeLog

+2008-02-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/35231
+	* gcc.c-torture/execute/pr35231.c: New testcase.
+
 2008-02-17  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/i386/pr32268.c (test_lt): Add noinline attribute.

gcc/testsuite/gcc.c-torture/execute/pr35231.c

+extern void abort(void);
+
+int __attribute__((noinline))
+foo(int bits_per_pixel, int depth)
+{
+  if ((bits_per_pixel | depth) == 1)
+    abort ();
+  return bits_per_pixel;
+}
+
+int main()
+{
+  if (foo(2, 0) != 2)
+    abort ();
+  return 0;
+}

gcc/tree-vrp.c

@@ -3753,7 +3753,11 @@ register_edge_assert_for (tree name, edge e, block_stmt_iterator si, tree cond)
 
       if (TREE_CODE (def_stmt) == GIMPLE_MODIFY_STMT
 	  && (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) == TRUTH_OR_EXPR
-	      || TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) == BIT_IOR_EXPR))
+	      /* For BIT_IOR_EXPR only if NAME == 0 both operands have
+		 necessarily zero value.  */
+	      || (comp_code == EQ_EXPR
+		  && (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1))
+		        == BIT_IOR_EXPR))))
 	{
 	  tree op0 = TREE_OPERAND (GIMPLE_STMT_OPERAND (def_stmt, 1), 0);
 	  tree op1 = TREE_OPERAND (GIMPLE_STMT_OPERAND (def_stmt, 1), 1);