fold-const.c (fold_binary): Fold (~X & C) eq/ne 0 as (X & C) ne/eq 0, where C is a single bit, i.e.

	* fold-const.c (fold_binary) <EQ_EXPR>:  Fold (~X & C) eq/ne 0 as
	(X & C) ne/eq 0, where C is a single bit, i.e. a power of two.
	Fold both "((X & C) ^ C) eq/ne 0" and "((X ^ C) & C) eq/ne 0"
	as (X & C) ne/eq 0.

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

From-SVN: r111471

4 files changed, 88 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a97c50a..d54a48f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,12 @@
 2006-02-26  Roger Sayle  <roger@eyesopen.com>
 
+	* fold-const.c (fold_binary) <EQ_EXPR>:  Fold (~X & C) eq/ne 0 as
+	(X & C) ne/eq 0, where C is a single bit, i.e. a power of two.
+	Fold both "((X & C) ^ C) eq/ne 0" and "((X ^ C) & C) eq/ne 0"
+	as (X & C) ne/eq 0.
+
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
 	PR middle-end/19983
 	* real.c (real_nan): Allow both 0x and 0X as hexadecimal prefixes.
 
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index e85534a..81d5f9f 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -9868,6 +9868,50 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 			    fold_build2 (BIT_XOR_EXPR, TREE_TYPE (arg1),
 					 TREE_OPERAND (arg0, 1), arg1));
 
+      /* Fold (~X & C) == 0 into (X & C) != 0 and (~X & C) != 0 into
+	 (X & C) == 0 when C is a single bit.  */
+      if (TREE_CODE (arg0) == BIT_AND_EXPR
+	  && TREE_CODE (TREE_OPERAND (arg0, 0)) == BIT_NOT_EXPR
+	  && integer_zerop (arg1)
+	  && integer_pow2p (TREE_OPERAND (arg0, 1)))
+	{
+	  tem = fold_build2 (BIT_AND_EXPR, TREE_TYPE (arg0),
+			     TREE_OPERAND (TREE_OPERAND (arg0, 0), 0),
+			     TREE_OPERAND (arg0, 1));
+	  return fold_build2 (code == EQ_EXPR ? NE_EXPR : EQ_EXPR,
+			      type, tem, arg1);
+	}
+
+      /* Fold ((X & C) ^ C) eq/ne 0 into (X & C) ne/eq 0, when the
+	 constant C is a power of two, i.e. a single bit.  */
+      if (TREE_CODE (arg0) == BIT_XOR_EXPR
+	  && TREE_CODE (TREE_OPERAND (arg0, 0)) == BIT_AND_EXPR
+	  && integer_zerop (arg1)
+	  && integer_pow2p (TREE_OPERAND (arg0, 1))
+	  && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1),
+			      TREE_OPERAND (arg0, 1), OEP_ONLY_CONST))
+	{
+	  tree arg00 = TREE_OPERAND (arg0, 0);
+	  return fold_build2 (code == EQ_EXPR ? NE_EXPR : EQ_EXPR, type,
+			      arg00, build_int_cst (TREE_TYPE (arg00), 0));
+	}
+
+      /* Likewise, fold ((X ^ C) & C) eq/ne 0 into (X & C) ne/eq 0,
+	 when is C is a power of two, i.e. a single bit.  */
+      if (TREE_CODE (arg0) == BIT_AND_EXPR
+	  && TREE_CODE (TREE_OPERAND (arg0, 0)) == BIT_XOR_EXPR
+	  && integer_zerop (arg1)
+	  && integer_pow2p (TREE_OPERAND (arg0, 1))
+	  && operand_equal_p (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1),
+			      TREE_OPERAND (arg0, 1), OEP_ONLY_CONST))
+	{
+	  tree arg000 = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
+	  tem = fold_build2 (BIT_AND_EXPR, TREE_TYPE (arg000),
+			     arg000, TREE_OPERAND (arg0, 1));
+	  return fold_build2 (code == EQ_EXPR ? NE_EXPR : EQ_EXPR, type,
+			      tem, build_int_cst (TREE_TYPE (tem), 0));
+	}
+
       if (integer_zerop (arg1)
 	  && tree_expr_nonzero_p (arg0))
         {
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index af21868..d0178e2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2006-02-26  Roger Sayle  <roger@eyesopen.com>
 
+	* gcc.dg/fold-eqandnot-1.c: New test case.
+
+2006-02-26  Roger Sayle  <roger@eyesopen.com>
+
 	PR middle-end/19983
 	* gcc.c-torture/execute/ieee/builtin-nan-1.c: New test case.
 
diff --git a/gcc/testsuite/gcc.dg/fold-eqandnot-1.c b/gcc/testsuite/gcc.dg/fold-eqandnot-1.c
new file mode 100644
index 0000000..5ed65e8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-eqandnot-1.c
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+int test1(int a)
+{
+  return !(a & 4);
+}
+
+int test2(int b)
+{
+  return (b & 4) == 0;
+}
+
+int test3(int c)
+{
+  return ((c & 4) ^ 4) != 0;
+}
+
+int test4(int d)
+{
+  return ((d ^ 4) & 4) != 0;
+}
+
+int test5(int e)
+{
+  return (~e & 4) != 0;
+}
+
+/* { dg-final { scan-tree-dump-times "\\(a \& 4\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(b \& 4\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(c \& 4\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(d \& 4\\) == 0" 1 "original" } } */
+/* { dg-final { scan-tree-dump-times "\\(e \& 4\\) == 0" 1 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */