re PR middle-end/42512 (integer wrong code bug with loop)

2010-01-09  Richard Guenther  <rguenther@suse.de>

	PR middle-end/42512
	* tree-scalar-evolution.c (interpret_loop_phi): Make sure
	the evolution is compatible with the initial condition.

	* gcc.c-torture/execute/pr42512.c: New testcase.

From-SVN: r155757

gcc/ChangeLog

+2010-01-09  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/42512
+	* tree-scalar-evolution.c (interpret_loop_phi): Make sure
+	the evolution is compatible with the initial condition.
+
 2010-01-09  Jakub Jelinek  <jakub@redhat.com>
 
 	* gcc.c (process_command): Update copyright notice dates.

gcc/testsuite/ChangeLog

+2010-01-09  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/42512
+	* gcc.c-torture/execute/pr42512.c: New testcase.
+
 2010-01-09  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/41298

gcc/testsuite/gcc.c-torture/execute/pr42512.c

+extern void abort (void);
+
+short g_3;
+
+int main (void)
+{
+    int l_2;
+    for (l_2 = -1; l_2 != 0; l_2 = (unsigned char)(l_2 - 1))
+      g_3 |= l_2;
+    if (g_3 != -1)
+      abort ();
+    return 0;
+}

gcc/tree-scalar-evolution.c

@@ -1642,6 +1642,23 @@ interpret_loop_phi (struct loop *loop, gimple loop_phi_node)
   init_cond = analyze_initial_condition (loop_phi_node);
   res = analyze_evolution_in_loop (loop_phi_node, init_cond);
 
+  /* Verify we maintained the correct initial condition throughout
+     possible conversions in the SSA chain.  */
+  if (res != chrec_dont_know)
+    {
+      tree new_init = res;
+      if (CONVERT_EXPR_P (res)
+	  && TREE_CODE (TREE_OPERAND (res, 0)) == POLYNOMIAL_CHREC)
+	new_init = fold_convert (TREE_TYPE (res),
+				 CHREC_LEFT (TREE_OPERAND (res, 0)));
+      else if (TREE_CODE (res) == POLYNOMIAL_CHREC)
+	new_init = CHREC_LEFT (res);
+      STRIP_USELESS_TYPE_CONVERSION (new_init);
+      gcc_assert (TREE_CODE (new_init) != POLYNOMIAL_CHREC);
+      if (!operand_equal_p (init_cond, new_init, 0))
+	return chrec_dont_know;
+    }
+
   return res;
 }