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-rw-r--r--gcc/ChangeLog6
-rw-r--r--gcc/fold-const.c7
-rw-r--r--gcc/testsuite/ChangeLog5
-rw-r--r--gcc/testsuite/gcc.dg/fold-reassoc-2.c14
4 files changed, 32 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f0b8348ead0..11ead219716 100644
--- 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 4f384a75344..7e619d6d1e5 100644
--- 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 2594b26508c..a4f4685f3d1 100644
--- 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
index 00000000000..e2dd100b71e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-reassoc-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-original" } */
+
+int foo (int i)
+{
+ return (i + 2) - (i + 1);
+}
+int bar (int i)
+{
+ return (i + 2) + ~i;
+}
+
+/* { dg-final { scan-tree-dump "return 1;" "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */