fold-const.c (fold): Fold (A & ~B) - (A & B) into (A ^ B) - B, where B is any power...

	* fold-const.c (fold): Fold (A & ~B) - (A & B) into
	(A ^ B) - B, where B is any power of 2 minus 1.

From-SVN: r71910

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 96a7ad4fa6565b0fc63dc7501e38e45a545d1764..307e9b76fd9d786e1a83b20af96d61041813a7d4 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2003-09-29  Kazu Hirata  <kazu@cs.umass.edu>
+
+       * fold-const.c (fold): Fold (A & ~B) - (A & B) into
+       (A ^ B) - B, where B is any power of 2 minus 1.
+
 Mon Sep 29 19:05:46 CEST 2003  Jan Hubicka  <jh@suse.cz>
 
        * libgcov.c (gcov_exit): Fix two pastos.

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 96d46263df280e72f38e9ba2e75aacbf872be4cd..3cfa54543602fd7525a7ea7a6c5f8e465696ca10 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6017,6 +6017,29 @@ fold (tree expr)
                                                  TREE_OPERAND (arg1, 1))),
                                    arg0));
            }
+
+         /* Fold (A & ~B) - (A & B) into (A ^ B) - B, , where B is
+            any power of 2 minus 1.  */
+         if (TREE_CODE (arg0) == BIT_AND_EXPR
+             && TREE_CODE (arg1) == BIT_AND_EXPR
+             && operand_equal_p (TREE_OPERAND (arg0, 0),
+                                 TREE_OPERAND (arg1, 0), 0)
+             && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
+             && TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST)
+           {
+             tree mask0 = TREE_OPERAND (arg0, 1);
+             tree mask1 = TREE_OPERAND (arg1, 1);
+             tree tem = fold (build1 (BIT_NOT_EXPR, type, mask0));
+             
+             if (operand_equal_p (tem, mask1, 0)
+                 && integer_pow2p (fold (build (PLUS_EXPR, type,
+                                                mask1, integer_one_node))))
+               {
+                 tem = fold (build (BIT_XOR_EXPR, type,
+                                    TREE_OPERAND (arg0, 0), mask1));
+                 return fold (build (MINUS_EXPR, type, tem, mask1));
+               }
+           }
        }
 
       /* See if ARG1 is zero and X - ARG1 reduces to X.  */