From: Luc Grosheintz <luc.groshei...@gmail.com>
In mdspan related code involving static extents, often the IndexType is
part of the template parameters, even though it's not needed.
This commit extracts the parts of _ExtentsStorage not related to
IndexType into a separate class _StaticExtents.
It also prefers passing the array of static extents, instead of the
whole extents object where possible.
The size of an object file compiled with -O2 that instantiates
Layout::mapping<extents<IndexType, Indices...>::stride
Layout::mapping<extents<IndexType, Indices...>::required_span_size
for the product of
- eight IndexTypes
- three Layouts,
- nine choices of Indices...
decreases by 19% from 69.2kB to 55.8kB.
libstdc++-v3/ChangeLog:
* include/std/mdspan (__mdspan::_StaticExtents): Extract non IndexType
related code from _ExtentsStorage.
(__mdspan::_ExtentsStorage): Use _StaticExtents.
(__mdspan::__static_extents): Return reference to NTTP of
_StaticExtents.
(__mdspan::__contains_zero): New overload.
(__mdspan::__exts_prod, __mdspan::__static_quotient): Use span to avoid
copying __sta_exts.
Reviewed-by: Tomasz Kamiński <tkami...@redhat.com>
Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
v3 adds following changes:
* updated __sta_exts variable to span, to preserve old behavior
* do not use braces to construct span
* __contains_zero for array uses dynamically sized span
LGTM.
libstdc++-v3/include/std/mdspan | 56 ++++++++++++++++++++++-----------
1 file changed, 37 insertions(+), 19 deletions(-)
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 5e79d4bfb59..08e6b8ff518 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -49,19 +49,14 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __mdspan
{
- template<typename _IndexType, array _Extents>
- class _ExtentsStorage
+ template<array _Extents>
+ class _StaticExtents
{
public:
static consteval bool
_S_is_dyn(size_t __ext) noexcept
{ return __ext == dynamic_extent; }
- template<typename _OIndexType>
- static constexpr _IndexType
- _S_int_cast(const _OIndexType& __other) noexcept
- { return _IndexType(__other); }
-
static constexpr size_t _S_rank = _Extents.size();
// For __r in [0, _S_rank], _S_dynamic_index[__r] is the number
@@ -99,6 +94,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static constexpr size_t
_S_static_extent(size_t __r) noexcept
{ return _Extents[__r]; }
+ };
+
+ template<typename _IndexType, array _Extents>
+ class _ExtentsStorage : public _StaticExtents<_Extents>
+ {
+ private:
+ using _S_base = _StaticExtents<_Extents>;
+
+ public:
+ using _S_base::_S_rank;
+ using _S_base::_S_rank_dynamic;
+ using _S_base::_S_dynamic_index;
+ using _S_base::_S_dynamic_index_inv;
+
+ template<typename _OIndexType>
+ static constexpr _IndexType
+ _S_int_cast(const _OIndexType& __other) noexcept
+ { return _IndexType(__other); }
constexpr _IndexType
_M_extent(size_t __r) const noexcept
@@ -157,9 +170,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return __exts[__i]; });
}
- static constexpr span<const size_t>
- _S_static_extents(size_t __begin, size_t __end) noexcept
- { return {_Extents.data() + __begin, _Extents.data() + __end}; }
+ static constexpr const array<size_t, _S_rank>&
+ _S_static_extents() noexcept
+ { return _Extents; }
constexpr span<const _IndexType>
_M_dynamic_extents(size_t __begin, size_t __end) const noexcept
@@ -185,10 +198,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
|| _Extent <= numeric_limits<_IndexType>::max();
template<typename _Extents>
- constexpr span<const size_t>
- __static_extents(size_t __begin = 0, size_t __end = _Extents::rank())
- noexcept
- { return _Extents::_S_storage::_S_static_extents(__begin, __end); }
+ constexpr const array<size_t, _Extents::rank()>&
+ __static_extents() noexcept
+ { return _Extents::_S_storage::_S_static_extents(); }
template<typename _Extents>
constexpr span<const typename _Extents::index_type>
@@ -314,8 +326,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
private:
- friend span<const size_t>
- __mdspan::__static_extents<extents>(size_t, size_t);
+ friend const array<size_t, rank()>&
+ __mdspan::__static_extents<extents>();
friend span<const index_type>
__mdspan::__dynamic_extents<extents>(const extents&, size_t, size_t);
@@ -340,6 +352,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return false;
}
+ template<typename _Tp, size_t _Nm>
+ consteval bool
+ __contains_zero(const array<_Tp, _Nm>& __exts) noexcept
+ { return __contains_zero(span<const _Tp>(__exts)); }
+
template<typename _Extents>
constexpr bool
__empty(const _Extents& __exts) noexcept
@@ -371,8 +388,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
size_t __ret = 1;
if constexpr (_Extents::rank_dynamic() != _Extents::rank())
{
- auto __sta_exts = __static_extents<_Extents>(__begin, __end);
- __ret = __static_extents_prod(__sta_exts);
+ std::span<const size_t> __sta_exts = __static_extents<_Extents>();
+ __ret = __static_extents_prod(__sta_exts.subspan(__begin,
+ __end - __begin));
if (__ret == 0)
return 0;
}
@@ -465,7 +483,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
consteval _IndexType
__static_quotient(_IndexType __nom = numeric_limits<_IndexType>::max())
{
- auto __sta_exts = __static_extents<_Extents>();
+ std::span<const size_t> __sta_exts = __static_extents<_Extents>();
for (auto __factor : __sta_exts)
{
if (__factor != dynamic_extent)
--
2.49.0
