re PR tree-optimization/15784 (fold misses binary optimization)

2005-03-03  James A. Morrison  <phython@gcc.gnu.org>

        PR tree-optimization/15784
        * fold-const.c (fold): Fold ~A + 1 to -1.  Fold -A - 1
        and -1 - A to ~A.

From-SVN: r95870

gcc/ChangeLog

+2005-03-03  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/15784
+	* fold-const.c (fold): Fold ~A + 1 to -1.  Fold -A - 1
+	and -1 - A to ~A.
+
 2005-03-03  David Edelsohn  <edelsohn@gnu.org>
 
 	* config/rs6000/predicates.md (branch_comparison_operator):

gcc/fold-const.c

@@ -7223,6 +7223,11 @@ fold (tree expr)
       if (TREE_CODE (arg0) == NEGATE_EXPR
 	  && reorder_operands_p (TREE_OPERAND (arg0, 0), arg1))
 	return fold (build2 (MINUS_EXPR, type, arg1, TREE_OPERAND (arg0, 0)));
+      /* Convert ~A + 1 to -A.  */
+      if (INTEGRAL_TYPE_P (type)
+	  && TREE_CODE (arg0) == BIT_NOT_EXPR
+	  && integer_onep (arg1))
+	return fold (build1 (NEGATE_EXPR, type, TREE_OPERAND (arg0, 0)));
 
       if (TREE_CODE (type) == COMPLEX_TYPE)
 	{
@@ -7661,6 +7666,16 @@ fold (tree expr)
 	  && reorder_operands_p (arg0, arg1))
 	return fold (build2 (MINUS_EXPR, type, negate_expr (arg1),
 			     TREE_OPERAND (arg0, 0)));
+      /* Convert -A - 1 to ~A.  */
+      if (INTEGRAL_TYPE_P (type)
+	  && TREE_CODE (arg0) == NEGATE_EXPR
+	  && integer_onep (arg1))
+	return fold (build1 (BIT_NOT_EXPR, type, TREE_OPERAND (arg0, 0)));
+
+      /* Convert -1 - A to ~A.  */
+      if (INTEGRAL_TYPE_P (type)
+	  && integer_all_onesp (arg0))
+	return fold (build1 (BIT_NOT_EXPR, type, arg1));
 
       if (TREE_CODE (type) == COMPLEX_TYPE)
 	{

gcc/testsuite/ChangeLog

+2005-03-03  James A. Morrison  <phython@gcc.gnu.org>
+
+	* gcc.dg/pr15784-4.c: New test.
+
 2005-03-03  Geoffrey Keating  <geoffk@apple.com>
 
 	* gcc.c-torture/execute/pr17133.c: New.

gcc/testsuite/gcc.dg/pr15784-4.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+int a (int x) {
+	return ~x + 1; /* -x */
+}
+
+int b (int x) {
+	return -x -1; /* ~x */
+}
+
+/* { dg-final { scan-tree-dump "~x;" "optimized" } } */
+/* { dg-final { scan-tree-dump "-x;" "optimized" } } */