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libstdc++: Fix incorrect use of memset in ranges::fill_n (PR 94017)

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When deciding whether to perform the memset optimization in ranges::fill_n, we
were crucially neglecting to check that the output pointer's value type is a
byte type.  This patch adds such a check to the problematic condition in
ranges::fill_n.

At the same time, this patch relaxes the overly conservative
__is_byte<_Tp>::__value check that requires the fill type be a byte type.  It's
overly conservative because it means we won't enable the memset optimization in
the following example

  char c[100];
  ranges::fill(c, 37);

because the fill type is deduced to be int here.  Rather than requiring that the
fill type be a byte type, it seems safe to just require the fill type be an
integral type, which is what this patch does.

libstdc++-v3/ChangeLog:

	PR libstdc++/94017
	* include/bits/ranges_algobase.h (__fill_n_fn::operator()): Refine
	condition for when to use memset, making sure to additionally check that
	the output pointer's value type is a non-volatile byte type.  Instead of
	requiring that the fill type is a byte type, just require that it's an
	integral type.
	* testsuite/20_util/specialized_algorithms/uninitialized_fill/94017.cc:
	New test.
	* testsuite/20_util/specialized_algorithms/uninitialized_fill_n/94017.cc:
	New test.
	* testsuite/25_algorithms/fill/94013.cc: Uncomment part that was blocked
	by PR 94017.
	* testsuite/25_algorithms/fill/94017.cc: New test.
	* testsuite/25_algorithms/fill_n/94017.cc: New test.
This commit is contained in:
Patrick Palka 2020-03-03 16:16:05 -05:00
parent 144dfc68d0
commit 712b182a8b
7 changed files with 328 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
libstdc++-v3/ChangeLog
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@ -1,5 +1,20 @@
2020-03-04 Patrick Palka <ppalka@redhat.com>
PR libstdc++/94017
* include/bits/ranges_algobase.h (__fill_n_fn::operator()): Refine
condition for when to use memset, making sure to additionally check that
the output pointer's value type is a non-volatile byte type. Instead of
requiring that the fill type is a byte type, just require that it's an
integral type.
* testsuite/20_util/specialized_algorithms/uninitialized_fill/94017.cc:
New test.
* testsuite/20_util/specialized_algorithms/uninitialized_fill_n/94017.cc:
New test.
* testsuite/25_algorithms/fill/94013.cc: Uncomment part of test that was
blocked by PR 94017.
* testsuite/25_algorithms/fill/94017.cc: New test.
* testsuite/25_algorithms/fill_n/94017.cc: New test.
LWG 3355 The memory algorithms should support move-only input iterators
introduced by P1207
* include/bits/ranges_uninitialized.h

7
libstdc++-v3/include/bits/ranges_algobase.h
View File

@ -516,8 +516,11 @@ namespace ranges
if (__n <= 0)
return __first;
// TODO: is __is_byte the best condition?
if constexpr (is_pointer_v<_Out> && __is_byte<_Tp>::__value)
// TODO: Generalize this optimization to contiguous iterators.
if constexpr (is_pointer_v<_Out>
// Note that __is_byte already implies !is_volatile.
&& __is_byte<remove_pointer_t<_Out>>::__value
&& integral<_Tp>)
{
__builtin_memset(__first, static_cast<unsigned char>(__value), __n);
return __first + __n;

77
libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill/94017.cc Normal file
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@ -0,0 +1,77 @@
// 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
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do run { target c++2a } }
#include <algorithm>
#include <memory>
#include <testsuite_hooks.h>
#include <testsuite_iterators.h>
using __gnu_test::test_output_range;
namespace ranges = std::ranges;
template<typename Out, auto value>
void
test01()
{
{
Out x[5];
ranges::uninitialized_fill(x, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
{
Out x[5];
test_output_range<Out> rx(x);
ranges::uninitialized_fill(x, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
}
int
main()
{
test01<char, 'a'>();
test01<char, 100>();
test01<char, 150>();
test01<char, 300>();
test01<char, 1000>();
test01<char, -10000L>();
test01<signed char, 'a'>();
test01<signed char, 100>();
test01<signed char, 150>();
test01<signed char, 300>();
test01<unsigned char, 'a'>();
test01<unsigned char, 100>();
test01<unsigned char, 150>();
test01<unsigned char, 300>();
test01<int, 'a'>();
test01<int, u8'a'>();
test01<int, (signed char)'a'>();
test01<int, (unsigned char)'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 500>();
test01<volatile char, 500>();
}

77
libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_fill_n/94017.cc Normal file
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@ -0,0 +1,77 @@
// 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
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do run { target c++2a } }
#include <algorithm>
#include <memory>
#include <testsuite_hooks.h>
#include <testsuite_iterators.h>
using __gnu_test::test_output_range;
namespace ranges = std::ranges;
template<typename Out, auto value>
void
test01()
{
{
Out x[5];
ranges::uninitialized_fill_n(x, 5, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
{
Out x[5];
test_output_range<Out> rx(x);
ranges::uninitialized_fill_n(x, 5, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
}
int
main()
{
test01<char, 'a'>();
test01<char, 100>();
test01<char, 150>();
test01<char, 300>();
test01<char, 1000>();
test01<char, -10000L>();
test01<signed char, 'a'>();
test01<signed char, 100>();
test01<signed char, 150>();
test01<signed char, 300>();
test01<unsigned char, 'a'>();
test01<unsigned char, 100>();
test01<unsigned char, 150>();
test01<unsigned char, 300>();
test01<int, 'a'>();
test01<int, u8'a'>();
test01<int, (signed char)'a'>();
test01<int, (unsigned char)'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 500>();
test01<volatile char, 500>();
}

5
libstdc++-v3/testsuite/25_algorithms/fill/94013.cc
View File

@ -33,9 +33,8 @@ test01()
c = 4;
std::ranges::fill(a, c);
VERIFY( a[0] == 4 && a[1] == 4 );
// currently fails, see PR 94017
// unsigned char c2 = 5;
// std::ranges::fill(a, c2);
unsigned char c2 = 5;
std::ranges::fill(a, c2);
#endif
}

76
libstdc++-v3/testsuite/25_algorithms/fill/94017.cc Normal file
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@ -0,0 +1,76 @@
// 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
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do run { target c++2a } }
#include <algorithm>
#include <testsuite_hooks.h>
#include <testsuite_iterators.h>
using __gnu_test::test_output_range;
namespace ranges = std::ranges;
template<typename Out, auto value>
void
test01()
{
{
Out x[5];
ranges::fill(x, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
{
Out x[5];
test_output_range<Out> rx(x);
ranges::fill(x, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
}
int
main()
{
test01<char, 'a'>();
test01<char, 100>();
test01<char, 150>();
test01<char, 300>();
test01<char, 1000>();
test01<char, -10000L>();
test01<signed char, 'a'>();
test01<signed char, 100>();
test01<signed char, 150>();
test01<signed char, 300>();
test01<unsigned char, 'a'>();
test01<unsigned char, 100>();
test01<unsigned char, 150>();
test01<unsigned char, 300>();
test01<int, 'a'>();
test01<int, u8'a'>();
test01<int, (signed char)'a'>();
test01<int, (unsigned char)'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 500>();
test01<volatile char, 500>();
}

76
libstdc++-v3/testsuite/25_algorithms/fill_n/94017.cc Normal file
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@ -0,0 +1,76 @@
// 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
// <http://www.gnu.org/licenses/>.
// { dg-options "-std=gnu++2a" }
// { dg-do run { target c++2a } }
#include <algorithm>
#include <testsuite_hooks.h>
#include <testsuite_iterators.h>
using __gnu_test::test_output_range;
namespace ranges = std::ranges;
template<typename Out, auto value>
void
test01()
{
{
Out x[5];
ranges::fill_n(x, 5, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
{
Out x[5];
test_output_range<Out> rx(x);
ranges::fill_n(x, 5, value);
VERIFY( ranges::count(x, static_cast<Out>(value)) == ranges::size(x) );
}
}
int
main()
{
test01<char, 'a'>();
test01<char, 100>();
test01<char, 150>();
test01<char, 300>();
test01<char, 1000>();
test01<char, -10000L>();
test01<signed char, 'a'>();
test01<signed char, 100>();
test01<signed char, 150>();
test01<signed char, 300>();
test01<unsigned char, 'a'>();
test01<unsigned char, 100>();
test01<unsigned char, 150>();
test01<unsigned char, 300>();
test01<int, 'a'>();
test01<int, u8'a'>();
test01<int, (signed char)'a'>();
test01<int, (unsigned char)'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 'a'>();
test01<volatile int, 500>();
test01<volatile char, 500>();
}