2007-02-24 Richard Guenther <rguenther@suse.de>

[pf3gnuchains/gcc-fork.git] / gcc / fold-const.c

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index ffd63cf..80c3c41 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -11203,6 +11203,24 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
                                         fold_convert (TREE_TYPE (arg0), arg1),
                                         TREE_OPERAND (arg0, 1)));
 
                                         fold_convert (TREE_TYPE (arg0), arg1),
                                         TREE_OPERAND (arg0, 1)));
 

+      /* Transform comparisons of the form X +- C CMP X.  */
+      if ((TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
+         && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0)
+         && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
+         && (INTEGRAL_TYPE_P (TREE_TYPE (arg0))
+             || POINTER_TYPE_P (TREE_TYPE (arg0))))
+       {
+         tree cst = TREE_OPERAND (arg0, 1);
+
+         if (code == EQ_EXPR
+             && !integer_zerop (cst))
+           return omit_two_operands (type, boolean_false_node,
+                                     TREE_OPERAND (arg0, 0), arg1);
+         else
+           return omit_two_operands (type, boolean_true_node,
+                                     TREE_OPERAND (arg0, 0), arg1);
+       }
+

       /* If we have X - Y == 0, we can convert that to X == Y and similarly
         for !=.  Don't do this for ordered comparisons due to overflow.  */
       if (TREE_CODE (arg0) == MINUS_EXPR
       /* If we have X - Y == 0, we can convert that to X == Y and similarly
         for !=.  Don't do this for ordered comparisons due to overflow.  */
       if (TREE_CODE (arg0) == MINUS_EXPR