re PR middle-end/55863 (Fails to fold (i + 2) - (i + 1) to 1)

2013-01-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/55863
	* fold-const.c (split_tree): Undo -X - 1 to ~X folding for
	reassociation.

	* gcc.dg/fold-reassoc-2.c: New testcase.

From-SVN: r194899

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f0b8348..11ead21 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2013-01-04  Richard Biener  <rguenther@suse.de>
+
+       PR middle-end/55863
+       * fold-const.c (split_tree): Undo -X - 1 to ~X folding for
+       reassociation.
+
 2013-01-03  John David Anglin  <dave.anglin@nrc-cnrc.gc.ca>
 
        PR target/53789

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 4f384a7..7e619d6 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -821,6 +821,13 @@ split_tree (tree in, enum tree_code code, tree *conp, tree *litp,
       if (neg_var_p)
        var = negate_expr (var);
     }
+  else if (TREE_CODE (in) == BIT_NOT_EXPR
+          && code == PLUS_EXPR)
+    {
+      /* -X - 1 is folded to ~X, undo that here.  */
+      *minus_litp = build_one_cst (TREE_TYPE (in));
+      var = negate_expr (TREE_OPERAND (in, 0));
+    }
   else if (TREE_CONSTANT (in))
     *conp = in;
   else

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 2594b26..a4f4685 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2013-01-04  Richard Biener  <rguenther@suse.de>
+
+       PR middle-end/55863
+       * gcc.dg/fold-reassoc-2.c: New testcase.
+
 2013-01-04  Tobias Burnus  <burnus@net-b.de>
 
        PR fortran/55763

diff --git a/gcc/testsuite/gcc.dg/fold-reassoc-2.c b/gcc/testsuite/gcc.dg/fold-reassoc-2.c
new file mode 100644 (file)
index 0000000..e2dd100
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-reassoc-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */\r
+/* { dg-options "-O -fdump-tree-original" } */\r
+\r
+int foo (int i)\r
+{\r
+  return (i + 2) - (i + 1);\r
+}\r
+int bar (int i)\r
+{\r
+  return (i + 2) + ~i;\r
+}\r
+\r
+/* { dg-final { scan-tree-dump "return 1;" "original" } } */\r
+/* { dg-final { cleanup-tree-dump "original" } } */\r