re PR tree-optimization/20130 (Fold a * -1 - 1 into ~a;)

2005-03-11  James A. Morrison  <phython@gcc.gnu.org>

       PR tree-optimization/20130
       * fold-const.c (fold): Fold x * -1 into -x.

From-SVN: r96283

gcc/ChangeLog

@@ -1,3 +1,8 @@
+2005-03-11  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/20130
+	* fold-const.c (fold): Fold x * -1 into -x.
+
 2005-03-11  Kaz Kojima  <kkojima@gcc.gnu.org>
 
 	PR rtl-optimization/20331

gcc/fold-const.c

@@ -7785,6 +7785,9 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1)
 	    return omit_one_operand (type, arg1, arg0);
 	  if (integer_onep (arg1))
 	    return non_lvalue (fold_convert (type, arg0));
+	  /* Transform x * -1 into -x.  */
+	  if (integer_all_onesp (arg1))
+	    return fold_convert (type, negate_expr (arg0));
 
 	  /* (a * (1 << b)) is (a << b)  */
 	  if (TREE_CODE (arg1) == LSHIFT_EXPR

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2005-03-10  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/20130
+	* gcc.dg/pr20130-1.c: New test.
+
 2005-03-10  Steve Ellcey  <sje@cup.hp.com>
 
 	PR target/20095

gcc/testsuite/gcc.dg/pr20130-1.c

@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-generic" } */
+int z (int a) {
+	return a * -1;
+}
+
+int x (int a) {
+	return -1 * a;
+}
+
+int y (int a) {
+	return -(-1 * -a);
+}
+/* { dg-final { scan-tree-dump-times "-a" 3 "generic" } } */