Move iterator_range to a new iterator-utils.h file

A later patch will add more iterator-related utilities.  Rather than
putting them all directly in coretypes.h, it seemed better to add a
new header file, here called "iterator-utils.h".  This preliminary
patch moves the existing iterator_range class there too.

I used the same copyright date range as coretypes.h “just to be sure”.

gcc/
	* coretypes.h (iterator_range): Move to...
	* iterator-utils.h: ...this new file.

2 files changed, 45 insertions, 17 deletions

diff --git a/gcc/coretypes.h b/gcc/coretypes.h
index da178b6..043df12 100644
--- a/gcc/coretypes.h
+++ b/gcc/coretypes.h
@@ -367,23 +367,6 @@ struct kv_pair
   const ValueType value;	/* the value of the name */
 };
 
-/* Iterator pair used for a collection iteration with range-based loops.  */
-
-template<typename T>
-struct iterator_range
-{
-public:
-  iterator_range (const T &begin, const T &end)
-    : m_begin (begin), m_end (end) {}
-
-  T begin () const { return m_begin; }
-  T end () const { return m_end; }
-
-private:
-  T m_begin;
-  T m_end;
-};
-
 #else
 
 struct _dont_use_rtx_here_;
@@ -491,6 +474,7 @@ typedef unsigned char uchar;
 #include "align.h"
 /* Most host source files will require the following headers.  */
 #if !defined (GENERATOR_FILE)
+#include "iterator-utils.h"
 #include "real.h"
 #include "fixed-value.h"
 #include "hash-table.h"
diff --git a/gcc/iterator-utils.h b/gcc/iterator-utils.h
new file mode 100644
index 0000000..0c95862
--- /dev/null
+++ b/gcc/iterator-utils.h
@@ -0,0 +1,44 @@
+// Iterator-related utilities.
+// Copyright (C) 2002-2020 Free Software Foundation, Inc.
+//
+// This file is part of GCC.
+//
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+//
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef GCC_ITERATOR_UTILS_H
+#define GCC_ITERATOR_UTILS_H 1
+
+// A half-open [begin, end) range of iterators.
+template<typename T>
+struct iterator_range
+{
+public:
+  using const_iterator = T;
+
+  iterator_range () = default;
+  iterator_range (const T &begin, const T &end)
+    : m_begin (begin), m_end (end) {}
+
+  T begin () const { return m_begin; }
+  T end () const { return m_end; }
+
+  explicit operator bool () const { return m_begin != m_end; }
+
+private:
+  T m_begin;
+  T m_end;
+};
+
+#endif