[gcc r16-4290] libstdc++: Improve and cleanup mdspan related code.
Tomasz Kaminski
tkaminsk@gcc.gnu.org
Wed Oct 8 10:31:47 GMT 2025
https://gcc.gnu.org/g:5733ecea0795b3b4f152dc33bb3aacd4ecfcf05f
commit r16-4290-g5733ecea0795b3b4f152dc33bb3aacd4ecfcf05f
Author: Luc Grosheintz <luc.grosheintz@gmail.com>
Date: Tue Sep 30 12:55:18 2025 +0200
libstdc++: Improve and cleanup mdspan related code.
The improvement is that in __index_type_cast, we don't need to check at
runtime if we know that _IndexType is smaller than _OIndexType.
The cleanup is whitespace (overlength lines) in <mdspan>, grouping is_always_foo
and is_foo together, and de-uglifying a variable in test code.
libstdc++-v3/ChangeLog:
* include/std/mdspan (__mdspan::__index_type_cast): Optimize by
skipping a __glibcxx_assert if it's know at compile-time.
(std::layout_left_padded, std::layout_righ_padded): Reorder
is_always_strided and is_unique member functions.
* testsuite/23_containers/mdspan/int_like.h: Rename _M_i to
value.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
Diff:
---
libstdc++-v3/include/std/mdspan | 42 +++++++++++++---------
.../testsuite/23_containers/mdspan/int_like.h | 12 +++----
2 files changed, 32 insertions(+), 22 deletions(-)
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 6714b19a8843..8d2421819a55 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -77,11 +77,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
if constexpr (std::is_integral_v<_OIndexType>)
{
- __glibcxx_assert(cmp_less_equal(__other,
- __gnu_cxx::__int_traits<_IndexType>::__max));
+ constexpr _IndexType __index_type_max
+ = __gnu_cxx::__int_traits<_IndexType>::__max;
+ constexpr _OIndexType __oindex_type_max
+ = __gnu_cxx::__int_traits<_OIndexType>::__max;
+
+ if constexpr (__index_type_max < __oindex_type_max)
+ __glibcxx_assert(cmp_less_equal(__other, __index_type_max));
+
if constexpr (std::is_signed_v<_OIndexType>)
__glibcxx_assert(__other >= 0);
- return std::move(__other);
+ return static_cast<_IndexType>(__other);
}
else
{
@@ -821,8 +827,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
mapping(const _LeftpadMapping& __other) noexcept
: mapping(__other.extents(), __mdspan::__internal_ctor{})
{
- constexpr size_t __ostride_sta = __mdspan::__get_static_stride<
- _LeftpadMapping>();
+ constexpr size_t __ostride_sta
+ = __mdspan::__get_static_stride<_LeftpadMapping>();
if constexpr (extents_type::rank() > 1)
{
@@ -981,7 +987,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _RightPaddedMapping>
requires __mdspan::__is_right_padded_mapping<_RightPaddedMapping>
&& is_constructible_v<extents_type,
- typename _RightPaddedMapping::extents_type>
+ typename _RightPaddedMapping::extents_type>
constexpr
explicit(!is_convertible_v<typename _RightPaddedMapping::extents_type,
extents_type>)
@@ -989,8 +995,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: mapping(__other.extents(), __mdspan::__internal_ctor{})
{
constexpr size_t __rank = extents_type::rank();
- constexpr size_t __ostride_sta = __mdspan::__get_static_stride<
- _RightPaddedMapping>();
+ constexpr size_t __ostride_sta
+ = __mdspan::__get_static_stride<_RightPaddedMapping>();
if constexpr (__rank > 1)
{
@@ -1441,7 +1447,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr static const size_t _S_unpad_end = _Rank;
template<typename _IndexType, size_t _StaticStride, size_t..._Extents>
- constexpr static auto _S_make_padded_extent(
+ constexpr static auto
+ _S_make_padded_extent(
extents<_IndexType, _StaticStride> __stride,
const extents<_IndexType, _Extents...>& __exts)
{
@@ -1467,7 +1474,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr static size_t _S_unpad_end = _Rank - 1;
template<typename _IndexType, size_t _StaticStride, size_t..._Extents>
- constexpr static auto _S_make_padded_extent(
+ constexpr static auto
+ _S_make_padded_extent(
extents<_IndexType, _StaticStride> __stride,
const extents<_IndexType, _Extents...>& __exts)
{
@@ -1792,7 +1800,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ }
template<__mdspan::__valid_index_type<index_type> _OIndexType>
- constexpr mapping(const extents_type& __exts, _OIndexType __pad)
+ constexpr
+ mapping(const extents_type& __exts, _OIndexType __pad)
: _M_storage(__exts,
__mdspan::__index_type_cast<index_type>(std::move(__pad)))
{ }
@@ -1881,10 +1890,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
is_always_unique() noexcept { return true; }
static constexpr bool
- is_always_strided() noexcept { return true; }
+ is_unique() noexcept { return true; }
static constexpr bool
- is_unique() noexcept { return true; }
+ is_always_strided() noexcept { return true; }
static constexpr bool
is_strided() noexcept { return true; }
@@ -1952,7 +1961,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ }
template<__mdspan::__valid_index_type<index_type> _OIndexType>
- constexpr mapping(const extents_type& __exts, _OIndexType __pad)
+ constexpr
+ mapping(const extents_type& __exts, _OIndexType __pad)
: _M_storage(__exts,
__mdspan::__index_type_cast<index_type>(std::move(__pad)))
{ }
@@ -2040,10 +2050,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
is_always_unique() noexcept { return true; }
static constexpr bool
- is_always_strided() noexcept { return true; }
+ is_unique() noexcept { return true; }
static constexpr bool
- is_unique() noexcept { return true; }
+ is_always_strided() noexcept { return true; }
static constexpr bool
is_strided() noexcept { return true; }
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h b/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
index 310dd8ddf207..e9172c134559 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
@@ -15,7 +15,7 @@ template<CustomIndexKind Kind>
public:
explicit
CustomIndexType(int i)
- : _M_i(i)
+ : value(i)
{ }
CustomIndexType() = delete;
@@ -31,25 +31,25 @@ template<CustomIndexKind Kind>
constexpr
operator int() const noexcept
requires (Kind == CustomIndexKind::Const)
- { return _M_i; }
+ { return value; }
constexpr
operator int() const
requires (Kind == CustomIndexKind::Throwing)
- { return _M_i; }
+ { return value; }
constexpr
operator int() noexcept
requires (Kind == CustomIndexKind::Mutating)
- { return _M_i; }
+ { return value; }
constexpr
operator int() && noexcept
requires (Kind == CustomIndexKind::RValue)
- { return _M_i; }
+ { return value; }
private:
- int _M_i;
+ int value;
};
using IntLike = CustomIndexType<CustomIndexKind::Const>;
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