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

	* 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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a97c50ade2fbbdbed5794691982313ea94480dbc..d54a48f64426d704573a059229c29fba71c7cd99 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+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

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index e85534ab2e1688bdfbc1891485c6d2a3a7ce1be8..81d5f9fa2512225c1eb461c7d11cf6b5fd5c1800 100644 (file)
--- 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 af218682acd2c549c9f19729735645e66e95e70b..d0178e22f55b7f7065cfc5378d2e909092667ac6 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-eqandnot-1.c: New test case.
+
 2006-02-26  Roger Sayle  <roger@eyesopen.com>
 
        PR middle-end/19983

diff --git a/gcc/testsuite/gcc.dg/fold-eqandnot-1.c b/gcc/testsuite/gcc.dg/fold-eqandnot-1.c
new file mode 100644 (file)
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" } } */