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merged 2 commits into from
Jul 15, 2025
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LWG Motion 11 #8074

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a509a02
P3480R6 std::simd is a range
mattkretz Jun 21, 2025
1ddaeac
[simd.syn] Add simd-iterator to header synopsis
tkoeppe Jul 15, 2025
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276 changes: 276 additions & 0 deletions source/numerics.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -16509,6 +16509,10 @@
template<size_t N> requires (has_single_bit(N))
constexpr flags<@\exposid{overaligned-flag}<N>@> flag_overaligned{};

// \ref{simd.iterator}, Class template \exposid{simd-iterator}
template<class V>
class @\exposidnc{simd-iterator}@; // \expos

// \ref{simd.class}, Class template \tcode{basic_simd}
template<class T, class Abi = @\exposid{native-abi}@<T>> class basic_simd;
template<class T, @\exposid{simd-size-type}@ N = @\exposid{simd-size-v}@<T, @\exposid{native-abi}@<T>>>
Expand Down Expand Up @@ -17204,6 +17208,262 @@
specialization \tcode{\exposid{overaligned-flag}<std::min(N1, N2)>}.
\end{itemdescr}

\rSec2[simd.iterator]{Class template \exposid{simd-iterator}}
\begin{codeblock}
namespace std::datapar {
template<class V>
class @\exposidnc{simd-iterator}@ { // \expos
V* @\exposid{data_}@ = nullptr; // \expos
@\exposid{simd-size-type}@ @\exposidnc{offset_}@ = 0; // \expos

constexpr @\exposidnc{simd-iterator}@(V& d, @\exposidnc{simd-size-type}@ off) noexcept; // \expos

public:
using value_type = typename V::value_type;
using iterator_category = input_iterator_tag;
using iterator_concept = random_access_iterator_tag;
using difference_type = @\exposid{simd-size-type}@;

constexpr @\exposid{simd-iterator}@() = default;

constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@&) = default;
constexpr @\exposid{simd-iterator}@& operator=(const @\exposid{simd-iterator}@&) = default;

constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@<remove_const_t<V>>&) requires is_const_v<V>;

constexpr value_type operator*() const;

constexpr @\exposid{simd-iterator}@& operator++();
constexpr @\exposid{simd-iterator}@ operator++(int);
constexpr @\exposid{simd-iterator}@& operator--();
constexpr @\exposid{simd-iterator}@ operator--(int);

constexpr @\exposid{simd-iterator}@& operator+=(difference_type n);
constexpr @\exposid{simd-iterator}@& operator-=(difference_type n);

constexpr value_type operator[](difference_type n) const;

friend constexpr bool operator==(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b) = default;
friend constexpr bool operator==(@\exposid{simd-iterator}@ a, default_sentinel_t) noexcept;
friend constexpr auto operator<=>(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);

friend constexpr @\exposid{simd-iterator}@ operator+(@\exposid{simd-iterator}@ i, difference_type n);
friend constexpr @\exposid{simd-iterator}@ operator+(difference_type n, @\exposid{simd-iterator}@ i);
friend constexpr @\exposid{simd-iterator}@ operator-(@\exposid{simd-iterator}@ i, difference_type n);

friend constexpr difference_type operator-(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
friend constexpr difference_type operator-(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
friend constexpr difference_type operator-(default_sentinel_t, @\exposid{simd-iterator}@ i) noexcept;
};
}
\end{codeblock}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@(V& d, @\exposid{simd-size-type}@ off) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Initializes \exposid{data_} with \tcode{addressof(d)} and \exposid{offset_} with \tcode{off}.
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@(const @\exposid{simd-iterator}@<remove_const_t<V>>& i) requires is_const_v<V>;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Initializes \exposid{data_} with \tcode{i.\exposid{data_}} and \exposid{offset_} with \tcode{i.\exposid{offset_}}.
\end{itemdescr}

\begin{itemdecl}
constexpr value_type operator*() const;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return (*\exposid{data_})[\exposid{offset_}];}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@& operator++();
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return *this += 1;}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@ operator++(int);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to:
\begin{codeblock}
@\exposid{simd-iterator}@ tmp = *this;
*this += 1;
return tmp;
\end{codeblock}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@& operator--();
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return *this -= 1;}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@ operator--(int);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to:
\begin{codeblock}
@\exposid{simd-iterator}@ tmp = *this;
*this -= 1;
return tmp;
\end{codeblock}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@& operator+=(difference_type n);
\end{itemdecl}

\begin{itemdescr}
\pnum
\expects
\tcode{\exposid{offset_} + n} is in the range \crange{0}{V::size()}.

\pnum
\effects
Equivalent to:
\begin{codeblock}
@\exposid{offset_}@ += n;
return *this;
\end{codeblock}
\end{itemdescr}

\begin{itemdecl}
constexpr @\exposid{simd-iterator}@& operator-=(difference_type n);
\end{itemdecl}

\begin{itemdescr}
\pnum
\expects
\tcode{\exposid{offset_} - n} is in the range \crange{0}{V::size()}.

\pnum
\effects
Equivalent to:
\begin{codeblock}
@\exposid{offset_}@ -= n;
return *this;
\end{codeblock}
\end{itemdescr}

\begin{itemdecl}
constexpr value_type operator[](difference_type n) const;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return (*\exposid{data_})[\exposid{offset_} + n];}
\end{itemdescr}

\begin{itemdecl}
friend constexpr bool operator==(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return i.\exposid{offset_} == V::size();}
\end{itemdescr}

\begin{itemdecl}
friend constexpr auto operator<=>(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
\end{itemdecl}

\begin{itemdescr}
\pnum
\expects
\tcode{a.\exposid{data_} == b.\exposid{data_}} is \tcode{true}.

\pnum
\effects
Equivalent to: \tcode{return a.\exposid{offset_} <=> b.\exposid{offset_};}
\end{itemdescr}

\begin{itemdecl}
friend constexpr @\exposid{simd-iterator}@ operator+(@\exposid{simd-iterator}@ i, difference_type n);
friend constexpr @\exposid{simd-iterator}@ operator+(difference_type n, @\exposid{simd-iterator}@ i);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return i += n;}
\end{itemdescr}

\begin{itemdecl}
friend constexpr @\exposid{simd-iterator}@ operator-(@\exposid{simd-iterator}@ i, difference_type n);
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return i -= n;}
\end{itemdescr}

\begin{itemdecl}
friend constexpr difference_type operator-(@\exposid{simd-iterator}@ a, @\exposid{simd-iterator}@ b);
\end{itemdecl}

\begin{itemdescr}
\pnum
\expects
\tcode{a.\exposid{data_} == b.\exposid{data_}} is \tcode{true}.

\pnum
\effects
Equivalent to: \tcode{return a.\exposid{offset_} - b.\exposid{offset_};}
\end{itemdescr}

\begin{itemdecl}
friend constexpr difference_type operator-(@\exposid{simd-iterator}@ i, default_sentinel_t) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return i.\exposid{offset_} - V::size();}
\end{itemdescr}


\begin{itemdecl}
friend constexpr difference_type operator-(default_sentinel_t, @\exposid{simd-iterator}@ i) noexcept;
\end{itemdecl}

\begin{itemdescr}
\pnum
\effects
Equivalent to: \tcode{return V::size() - i.\exposid{offset_};}
\end{itemdescr}

\rSec2[simd.class]{Class template \tcode{basic_simd}}

\rSec3[simd.overview]{Class template \tcode{basic_simd} overview}
Expand All @@ -17215,6 +17475,14 @@
using value_type = T;
using mask_type = basic_simd_mask<sizeof(T), Abi>;
using abi_type = Abi;
using @\libmember{iterator}{basic_simd}@ = @\exposid{simd-iterator}@<basic_simd>;
using @\libmember{const_iterator}{basic_simd}@ = @\exposid{simd-iterator}@<const basic_simd>;

constexpr iterator @\libmember{begin}{basic_simd}@() noexcept { return {*this, 0}; }
constexpr const_iterator @\libmember{begin}{basic_simd}@() const noexcept { return {*this, 0}; }
constexpr const_iterator @\libmember{cbegin}{basic_simd}@() const noexcept { return {*this, 0}; }
constexpr default_sentinel_t @\libmember{end}{basic_simd}@() const noexcept { return {}; }
constexpr default_sentinel_t @\libmember{cend}{basic_simd}@() const noexcept { return {}; }

static constexpr integral_constant<@\exposid{simd-size-type}@, @\exposid{simd-size-v}@<T, Abi>> size {};

Expand Down Expand Up @@ -19101,6 +19369,14 @@
public:
using value_type = bool;
using abi_type = Abi;
using @\libmember{iterator}{basic_simd_mask}@ = @\exposid{simd-iterator}@<basic_simd_mask>;
using @\libmember{const_iterator}{basic_simd_mask}@ = @\exposid{simd-iterator}@<const basic_simd_mask>;

constexpr iterator @\libmember{begin}{basic_simd_mask}@() noexcept { return {*this, 0}; }
constexpr const_iterator @\libmember{begin}{basic_simd_mask}@() const noexcept { return {*this, 0}; }
constexpr const_iterator @\libmember{cbegin}{basic_simd_mask}@() const noexcept { return {*this, 0}; }
constexpr default_sentinel_t @\libmember{end}{basic_simd_mask}@() const noexcept { return {}; }
constexpr default_sentinel_t @\libmember{cend}{basic_simd_mask}@() const noexcept { return {}; }

static constexpr integral_constant<@\exposid{simd-size-type}@, @\exposid{simd-size-v}@<@\exposid{integer-from}@<Bytes>, Abi>>
size {};
Expand Down