[partial backport of gcc-4.9/trunk r198772, adds build_minus_one_cst
 needed by PR57980 fix <mikpe@it.uu.se>]

gcc/

2013-05-10  Marc Glisse  <marc.glisse@inria.fr>

	* tree.c (build_minus_one_cst): New function.
	* tree.h (build_minus_one_cst): Declare new function.

--- gcc-4.8.1/gcc/tree.c.~1~	2013-05-23 15:25:23.000000000 +0200
+++ gcc-4.8.1/gcc/tree.c	2013-08-10 12:36:59.701381382 +0200
@@ -1619,6 +1619,45 @@ build_one_cst (tree type)
     }
 }
 
+/* Return a constant of arithmetic type TYPE which is the
+   opposite of the multiplicative identity of the set TYPE.  */
+
+tree
+build_minus_one_cst (tree type)
+{
+  switch (TREE_CODE (type))
+    {
+    case INTEGER_TYPE: case ENUMERAL_TYPE: case BOOLEAN_TYPE:
+    case POINTER_TYPE: case REFERENCE_TYPE:
+    case OFFSET_TYPE:
+      return build_int_cst (type, -1);
+
+    case REAL_TYPE:
+      return build_real (type, dconstm1);
+
+    case FIXED_POINT_TYPE:
+      /* We can only generate 1 for accum types.  */
+      gcc_assert (ALL_SCALAR_ACCUM_MODE_P (TYPE_MODE (type)));
+      return build_fixed (type, fixed_from_double_int (double_int_minus_one,
+						       TYPE_MODE (type)));
+
+    case VECTOR_TYPE:
+      {
+	tree scalar = build_minus_one_cst (TREE_TYPE (type));
+
+	return build_vector_from_val (type, scalar);
+      }
+
+    case COMPLEX_TYPE:
+      return build_complex (type,
+			    build_minus_one_cst (TREE_TYPE (type)),
+			    build_zero_cst (TREE_TYPE (type)));
+
+    default:
+      gcc_unreachable ();
+    }
+}
+
 /* Build 0 constant of type TYPE.  This is used by constructor folding
    and thus the constant should be represented in memory by
    zero(es).  */
--- gcc-4.8.1/gcc/tree.h.~1~	2013-05-23 15:25:23.000000000 +0200
+++ gcc-4.8.1/gcc/tree.h	2013-08-10 12:36:58.081384429 +0200
@@ -4760,6 +4760,7 @@ extern tree build_constructor_from_list
 extern tree build_real_from_int_cst (tree, const_tree);
 extern tree build_complex (tree, tree, tree);
 extern tree build_one_cst (tree);
+extern tree build_minus_one_cst (tree);
 extern tree build_zero_cst (tree);
 extern tree build_string (int, const char *);
 extern tree build_tree_list_stat (tree, tree MEM_STAT_DECL);