re PR tree-optimization/50729 (Silent code gen fault: Value range propagation…

re PR tree-optimization/50729 (Silent code gen fault: Value range propagation seems to propagate values across narrowing/widening)

2011-10-17  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/50729
	* tree-vrp.c (extract_range_from_unary_expr_1): Remove
	redundant test.
	(simplify_conversion_using_ranges): Properly test the
	intermediate result.

	* gcc.dg/torture/pr50729.c: New testcase.

From-SVN: r180087

gcc/ChangeLog

+2011-10-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/50729
+	* tree-vrp.c (extract_range_from_unary_expr_1): Remove
+	redundant test.
+	(simplify_conversion_using_ranges): Properly test the
+	intermediate result.
+
 2011-10-15  Tom Tromey  <tromey@redhat.com>
 	    Dodji Seketeli  <dodji@redhat.com>
 

gcc/testsuite/ChangeLog

+2011-10-17  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/50729
+	* gcc.dg/torture/pr50729.c: New testcase.
+
 2011-10-15  Tom Tromey  <tromey@redhat.com>
 	    Dodji Seketeli  <dodji@redhat.com>
 

gcc/testsuite/gcc.dg/torture/pr50729.c

+/* { dg-do run } */
+/* { dg-require-effective-target int32plus } */
+
+extern void abort (void);
+unsigned short __attribute__((noinline))
+foo (int i)
+{
+  if (i >= 0
+      && i <= 0x400000)
+    return (unsigned short)(signed char)i;
+  return i;
+}
+int main()
+{
+  int i;
+  for (i = 0; i < 0xffff; ++i)
+    if (foo(i) != (unsigned short)(signed char) i)
+      abort ();
+  return 0;
+}

gcc/tree-vrp.c

@@ -2913,15 +2913,10 @@ extract_range_from_unary_expr_1 (value_range_t *vr,
 	 determining if it evaluates to NULL [0, 0] or non-NULL (~[0, 0]).  */
       if (POINTER_TYPE_P (type))
 	{
-	  if (CONVERT_EXPR_CODE_P (code))
-	    {
-	      if (range_is_nonnull (&vr0))
-		set_value_range_to_nonnull (vr, type);
-	      else if (range_is_null (&vr0))
-		set_value_range_to_null (vr, type);
-	      else
-		set_value_range_to_varying (vr);
-	    }
+	  if (range_is_nonnull (&vr0))
+	    set_value_range_to_nonnull (vr, type);
+	  else if (range_is_null (&vr0))
+	    set_value_range_to_null (vr, type);
 	  else
 	    set_value_range_to_varying (vr);
 	  return;
@@ -7288,10 +7283,17 @@ simplify_conversion_using_ranges (gimple stmt)
 			      TYPE_UNSIGNED (TREE_TYPE (middleop)));
   middlemax = double_int_ext (innermax, TYPE_PRECISION (TREE_TYPE (middleop)),
 			      TYPE_UNSIGNED (TREE_TYPE (middleop)));
-  /* If the middle values do not represent a proper range fail.  */
-  if (double_int_cmp (middlemin, middlemax,
-		      TYPE_UNSIGNED (TREE_TYPE (middleop))) > 0)
+  /* If the middle values are not equal to the original values fail.
+     But only if the inner cast truncates (thus we ignore differences
+     in extension to handle the case going from a range to an anti-range
+     and back).  */
+  if ((TYPE_PRECISION (TREE_TYPE (innerop))
+       > TYPE_PRECISION (TREE_TYPE (middleop)))
+      && (!double_int_equal_p (innermin, middlemin)
+	  || !double_int_equal_p (innermax, middlemax)))
     return false;
+  /* Require that the final conversion applied to both the original
+     and the intermediate range produces the same result.  */
   if (!double_int_equal_p (double_int_ext (middlemin,
 					   TYPE_PRECISION (finaltype),
 					   TYPE_UNSIGNED (finaltype)),