fold-const.c (fold_binary): Fold (X & 1) ^ 1 as (X & 1) == 0.

	* fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
	(X & 1) == 0.
	<BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.

	* gcc.dg/fold-even-1.c: New test case.

From-SVN: r111454

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index ead872d398c85034f10bac04e3bf18c7703cb3f0..90cff90c880b9de40e0c31f20d74b15d77f9ac7b 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
+       * fold-const.c (fold_binary) <BIT_XOR_EXPR>: Fold (X & 1) ^ 1 as
+       (X & 1) == 0.
+       <BIT_AND_EXPR>: Fold (X ^ 1) & 1 and ~X & 1 as (X & 1) == 0.
+
 2006-02-26  Roger Sayle  <roger@eyesopen.com>
            James A. Morrison  <phython@gcc.gnu.org>
 

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 7eb4d914e92baf12433beb057d855fceaea1657d..e85534ab2e1688bdfbc1891485c6d2a3a7ce1be8 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -8740,6 +8740,13 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
                            fold_convert (type, TREE_OPERAND (arg0, 0)),
                            fold_convert (type, TREE_OPERAND (arg1, 0)));
 
+      /* Fold (X & 1) ^ 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_AND_EXPR
+         && integer_onep (TREE_OPERAND (arg0, 1))
+         && integer_onep (arg1))
+       return fold_build2 (EQ_EXPR, type, arg0,
+                           build_int_cst (TREE_TYPE (arg0), 0));
+
       /* See if this can be simplified into a rotate first.  If that
         is unsuccessful continue in the association code.  */
       goto bit_rotate;
@@ -8792,6 +8799,28 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
          && reorder_operands_p (arg0, TREE_OPERAND (arg1, 0)))
        return omit_one_operand (type, arg0, TREE_OPERAND (arg1, 0));
 
+      /* Fold (X ^ 1) & 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_XOR_EXPR
+         && integer_onep (TREE_OPERAND (arg0, 1))
+         && integer_onep (arg1))
+       {
+         tem = TREE_OPERAND (arg0, 0);
+         return fold_build2 (EQ_EXPR, type,
+                             fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
+                                          build_int_cst (TREE_TYPE (tem), 1)),
+                             build_int_cst (TREE_TYPE (tem), 0));
+       }
+      /* Fold ~X & 1 as (X & 1) == 0.  */
+      if (TREE_CODE (arg0) == BIT_NOT_EXPR
+         && integer_onep (arg1))
+       {
+         tem = TREE_OPERAND (arg0, 0);
+         return fold_build2 (EQ_EXPR, type,
+                             fold_build2 (BIT_AND_EXPR, TREE_TYPE (tem), tem,
+                                          build_int_cst (TREE_TYPE (tem), 1)),
+                             build_int_cst (TREE_TYPE (tem), 0));
+       }
+
       t1 = distribute_bit_expr (code, type, arg0, arg1);
       if (t1 != NULL_TREE)
        return t1;

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index deb3000d167b21e3c4b26157c3dc7e85edd2d91d..a93b73c66374498d484d97b59eaeaf79f2915325 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
+       * gcc.dg/fold-even-1.c: New test case.
+
 2006-02-26  Roger Sayle  <roger@eyesopen.com>
 
        PR middle-end/21137

diff --git a/gcc/testsuite/gcc.dg/fold-even-1.c b/gcc/testsuite/gcc.dg/fold-even-1.c
new file mode 100644 (file)
index 0000000..8e6539c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-even-1.c
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+int test1(int a)
+{
+  return !(a & 1);
+}
+
+int test2(int b)
+{
+  return (b & 1) == 0;
+}
+
+int test3(int c)
+{
+  return (c & 1) ^ 1;
+}
+
+int test4(int d)
+{
+  return (d ^ 1) & 1;
+}
+
+int test5(int e)
+{
+  return ~e & 1;
+}
+
+/* { dg-final { scan-tree-dump-times "\\(a \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(b \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(c \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(d \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(e \& 1\\) == 0" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */