re PR tree-optimization/38405 ((silent failure) handling bitfield in ternary)

2008-12-07  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/38405
	* tree-vrp.c (simplify_truth_ops_using_ranges): Make sure to
	not sign-extend truth values.

From-SVN: r142539

gcc/ChangeLog

+2008-12-07  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38405
+	* tree-vrp.c (simplify_truth_ops_using_ranges): Make sure to
+	not sign-extend truth values.
+
 2008-12-07  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* tree-sra.c (scalarize_use): Create another temporary with the proper

gcc/tree-vrp.c

@@ -6512,6 +6512,12 @@ simplify_truth_ops_using_ranges (gimple_stmt_iterator *gsi, gimple stmt)
     !useless_type_conversion_p (TREE_TYPE (gimple_assign_lhs (stmt)),
 			        TREE_TYPE (op0));
 
+  /* Make sure to not sign-extend -1 as a boolean value.  */
+  if (need_conversion
+      && !TYPE_UNSIGNED (TREE_TYPE (op0))
+      && TYPE_PRECISION (TREE_TYPE (op0)) == 1)
+    return false;
+
   switch (rhs_code)
     {
     case TRUTH_AND_EXPR: