Re: [PATCH 2/4] libstdc++: Reduce the size of a subrange with empty sentinel type

[Jonathan Wakely via Gcc-patches]

On 28/09/20 00:48 -0400, Patrick Palka via Libstdc++ wrote:

libstdc++-v3/ChangeLog:

* include/bits/ranges_util.h (subrange::_M_end): Give it
[[no_unique_adcress]].
* testsuite/std/ranges/subrange/sizeof.cc: New test.


OK.


libstdc++-v3/include/bits/ranges_util.h   |  2 +-
.../testsuite/std/ranges/subrange/sizeof.cc   | 28 +++
2 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc

diff --git a/libstdc++-v3/include/bits/ranges_util.h 
b/libstdc++-v3/include/bits/ranges_util.h
index 694ae796399..a98658ff5c8 100644
--- a/libstdc++-v3/include/bits/ranges_util.h
+++ b/libstdc++-v3/include/bits/ranges_util.h
@@ -208,7 +208,7 @@ namespace ranges
= _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>;

  _It _M_begin = _It();
-  _Sent _M_end = _Sent();
+  [[no_unique_address]] _Sent _M_end = _Sent();

  template
struct _Size
diff --git a/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc 
b/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc
new file mode 100644
index 000..7e95e196c6c
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc
@@ -0,0 +1,28 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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.
+
+// This library 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 this library; see the file COPYING3.  If not see
+// .
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include 
+#include 
+
+// Verify we optimize away the 'end' data member of a subrange with an empty
+// sentinel type.
+static_assert(sizeof(std::ranges::subrange,
+  std::default_sentinel_t>)
+ == sizeof(std::counted_iterator));
--
2.28.0.618.g9bc233ae1c

[PATCH 2/4] libstdc++: Reduce the size of a subrange with empty sentinel type

[Patrick Palka via Gcc-patches]

libstdc++-v3/ChangeLog:

* include/bits/ranges_util.h (subrange::_M_end): Give it
[[no_unique_adcress]].
* testsuite/std/ranges/subrange/sizeof.cc: New test.
---
 libstdc++-v3/include/bits/ranges_util.h   |  2 +-
 .../testsuite/std/ranges/subrange/sizeof.cc   | 28 +++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc

diff --git a/libstdc++-v3/include/bits/ranges_util.h 
b/libstdc++-v3/include/bits/ranges_util.h
index 694ae796399..a98658ff5c8 100644
--- a/libstdc++-v3/include/bits/ranges_util.h
+++ b/libstdc++-v3/include/bits/ranges_util.h
@@ -208,7 +208,7 @@ namespace ranges
= _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>;
 
   _It _M_begin = _It();
-  _Sent _M_end = _Sent();
+  [[no_unique_address]] _Sent _M_end = _Sent();
 
   template
struct _Size
diff --git a/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc 
b/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc
new file mode 100644
index 000..7e95e196c6c
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/subrange/sizeof.cc
@@ -0,0 +1,28 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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.
+
+// This library 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 this library; see the file COPYING3.  If not see
+// .
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include 
+#include 
+
+// Verify we optimize away the 'end' data member of a subrange with an empty
+// sentinel type.
+static_assert(sizeof(std::ranges::subrange,
+  std::default_sentinel_t>)
+ == sizeof(std::counted_iterator));
-- 
2.28.0.618.g9bc233ae1c