2005-02-15 James A. Morrison <phython@gcc.gnu.org>

        * fold-const.c (fold): Fold -(~A) to A + 1.  Fold ~(-A) to A - 1.
        Fold ~(A - 1) and ~(A + -1) to -A.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@95074 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 67 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 42e602b3687..a3b955e363e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 2005-02-15  James A. Morrison  <phython@gcc.gnu.org>
 
+	* fold-const.c (fold): Fold -(~A) to A + 1.  Fold ~(-A) to A - 1.
+	Fold ~(A - 1) and ~(A + -1) to -A.
+
+2005-02-15  James A. Morrison  <phython@gcc.gnu.org>
+
 	PR pch/14940
 	PR target/19300
 	* config/host-linux.c (linux_gt_pch_use_address): Copy from
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 03285ec523b..ef31a32f54e 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6931,6 +6931,10 @@ fold (tree expr)
     case NEGATE_EXPR:
       if (negate_expr_p (arg0))
 	return fold_convert (type, negate_expr (arg0));
+      /* Convert - (~A) to A + 1.  */
+      if (INTEGRAL_TYPE_P (type) && TREE_CODE (arg0) == BIT_NOT_EXPR)
+	return fold (build2 (PLUS_EXPR, type, TREE_OPERAND (arg0, 0),
+			     build_int_cst (type, 1)));
       return t;
 
     case ABS_EXPR:
@@ -6985,6 +6989,17 @@ fold (tree expr)
         return fold_not_const (arg0, type);
       else if (TREE_CODE (arg0) == BIT_NOT_EXPR)
 	return TREE_OPERAND (arg0, 0);
+      /* Convert ~ (-A) to A - 1.  */
+      else if (INTEGRAL_TYPE_P (type) && TREE_CODE (arg0) == NEGATE_EXPR)
+	return fold (build2 (MINUS_EXPR, type, TREE_OPERAND (arg0, 0),
+			     build_int_cst (type, 1)));
+      /* Convert ~ (A - 1) or ~ (A + -1) to -A.  */
+      else if (INTEGRAL_TYPE_P (type)
+	       && ((TREE_CODE (arg0) == MINUS_EXPR
+		    && integer_onep (TREE_OPERAND (arg0, 1)))
+		   || (TREE_CODE (arg0) == PLUS_EXPR
+		       && integer_all_onesp (TREE_OPERAND (arg0, 1)))))
+	return fold (build1 (NEGATE_EXPR, type, TREE_OPERAND (arg0, 0)));
       return t;
 
     case PLUS_EXPR:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 1a66c5eddfb..fc56108b49e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2005-02-15  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/15785
+	* gcc.dg/pr15785-1.c: New test.
+
 2005-02-15  Alexandre Oliva  <aoliva@redhat.com>
 
 	PR c++/17788
diff --git a/gcc/testsuite/gcc.dg/pr15785-1.c b/gcc/testsuite/gcc.dg/pr15785-1.c
new file mode 100644
index 00000000000..47cd3d7b01b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr15785-1.c
@@ -0,0 +1,42 @@
+/* { dg-do link } */
+
+extern void link_error ();
+
+void a (int x) {
+	if (~ (~x) - x)
+		link_error ();
+}
+void b (int x) {
+	if (- (-x) - x)
+		link_error ();
+}
+
+void c (int x) {
+	if (!(- (~x) - x))
+		link_error ();
+}
+
+void d (int x) {
+	if (!(~ (-x) - x))
+		link_error ();
+}
+
+void e (int x) {
+	if (x + ~(x - 1))
+		link_error ();
+}
+
+void f (int x) {
+	if (x + ~(x + (-1)))
+		link_error ();
+}
+
+int main (int argc, char *argv[]) {
+	a(argc);
+	b(argc);
+	c(argc);
+	d(argc);
+	e(argc);
+	f(argc);
+	return 0;
+}