re PR middle-end/35163 (folding comparison loses cast)

2008-02-12  Richard Guenther  <rguenther@suse.de>

	PR middle-end/35163
	* fold-const.c (fold_widened_comparison): Use get_unwidened in
	value-preserving mode.  Disallow final truncation.

	* gcc.c-torture/execute/pr35163.c: New testcase.

From-SVN: r132269

gcc/ChangeLog

+2008-02-12  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/35163
+	* fold-const.c (fold_widened_comparison): Use get_unwidened in
+	value-preserving mode.  Disallow final truncation.
+
 2008-02-12  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR middle-end/35136

gcc/fold-const.c

@@ -7045,12 +7045,14 @@ fold_widened_comparison (enum tree_code code, tree type, tree arg0, tree arg1)
   if (TYPE_PRECISION (TREE_TYPE (arg0)) <= TYPE_PRECISION (shorter_type))
     return NULL_TREE;
 
-  arg1_unw = get_unwidened (arg1, shorter_type);
+  arg1_unw = get_unwidened (arg1, NULL_TREE);
 
   /* If possible, express the comparison in the shorter mode.  */
   if ((code == EQ_EXPR || code == NE_EXPR
        || TYPE_UNSIGNED (TREE_TYPE (arg0)) == TYPE_UNSIGNED (shorter_type))
       && (TREE_TYPE (arg1_unw) == shorter_type
+	  || (TYPE_PRECISION (shorter_type)
+	      >= TYPE_PRECISION (TREE_TYPE (arg1_unw)))
 	  || (TREE_CODE (arg1_unw) == INTEGER_CST
 	      && (TREE_CODE (shorter_type) == INTEGER_TYPE
 		  || TREE_CODE (shorter_type) == BOOLEAN_TYPE)

gcc/testsuite/ChangeLog

+2008-02-12  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/35163
+	* gcc.c-torture/execute/pr35163.c: New testcase.
+
 2008-02-12  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc.target/i386/asm-3.c: Fix dg-skip-if for all 32bit PIC targets.

gcc/testsuite/gcc.c-torture/execute/pr35163.c

+extern void abort(void);
+
+int main()
+{
+  signed char a = -30;
+  signed char b = -31;
+  if (a > (unsigned short)b)
+    abort ();
+  return 0;
+}
+