On Fri, 03 Oct 2025 at 12:48 +0200, Tomasz Kamiński wrote:
From: Luc Grosheintz <[email protected]>
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> 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.
* testsuite/23_containers/mdspan/int_like.h: Rename _M_i to
value.
Reviewed-by: Tomasz Kamiński <[email protected]>
Signed-off-by: Luc Grosheintz <[email protected]>
---
v2 revers few whitespace changes.
libstdc++-v3/include/std/mdspan | 16 +++++++++++-----
.../testsuite/23_containers/mdspan/int_like.h | 12 ++++++------
2 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index ce7e4178f67..469d4c3cb6c 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);
+ __glibcxx_assert(__other >= 0);
+ return static_cast<_IndexType>(std::move(__other));
Do we need the std::move here, if we know that __other has an integral
type?
}
else
{
@@ -981,7 +987,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<class _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>)
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
b/libstdc++-v3/testsuite/23_containers/mdspan/int_like.h
index 310dd8ddf20..e9172c13455 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>;
--
2.51.0
