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        Atomic Read-Modify-Write Improvements
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    <div id="doc" class="markdown-body container-fluid comment-enabled" data-hard-breaks="true"><p><strong><span>Document number</span></strong><span>: P3306R0.</span><br>
<strong><span>Date</span></strong><span>: 2024-5-21.</span><br>
<strong><span>Authors</span></strong><span>: Gonzalo Brito Gadeschi, Damien Lebrun-Grandie.</span><br>
<strong><span>Reply to</span></strong><span>: Gonzalo Brito Gadeschi &lt;gonzalob _at_ </span><a href="http://nvidia.com" target="_blank" rel="noopener"><span>nvidia.com</span></a><span>&gt;.</span><br>
<strong><span>Audience</span></strong><span>: SG1, SG6.</span></p><style>
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</style><p><big><span>Table of Contents</span></big></p><p><span class="toc"><ul>
<li><a href="#Atomic-Read-Modify-Write-Improvements" title="Atomic Read-Modify-Write Improvements">Atomic Read-Modify-Write Improvements</a></li>
<li><a href="#Motivation" title="Motivation">Motivation</a></li>
<li><a href="#Design" title="Design">Design</a></li>
<li><a href="#Wording" title="Wording">Wording</a></li>
</ul>
</span></p><h1 id="Atomic-Read-Modify-Write-Improvements" data-id="Atomic-Read-Modify-Write-Improvements"><a class="anchor hidden-xs" href="#Atomic-Read-Modify-Write-Improvements" title="Atomic-Read-Modify-Write-Improvements"><span class="octicon octicon-link"></span></a><span>Atomic Read-Modify-Write Improvements</span></h1><p><span>Extends read-modify-write atomic APIs with commonly requested functionality that is already available in some pre-existing implementations as an extension: integer shl, shr, mod, nand, div, mul, and floating-point div and mul.</span></p><h1 id="Motivation" data-id="Motivation"><a class="anchor hidden-xs" href="#Motivation" title="Motivation"><span class="octicon octicon-link"></span></a><span>Motivation</span></h1><p><span>Without these extensions, users are required to implement this functionality by themselves on top of the atomic types, e.g., via user-specified CAS-loops. These loops complicate compiler optimizations and high-quality forward progress.</span></p><h1 id="Design" data-id="Design"><a class="anchor hidden-xs" href="#Design" title="Design"><span class="octicon octicon-link"></span></a><span>Design</span></h1><p><span>The following APIs are commonly requested, and available in some implementations, like </span><a href="https://kokkos.org/kokkos-core-wiki/API/core/atomics/atomic_fetch_op.html" target="_blank" rel="noopener"><span>Kokkos atomic_fetch_</span>&lt;op&gt;</a><span> or </span><a href="https://doc.rust-lang.org/std/sync/atomic/struct.AtomicU8.html" target="_blank" rel="noopener"><span>Rust's Atomic</span></a><span>:</span></p><ul>
<li><span>Integer shl, shr, mod, nand.</span></li>
<li><span>Integer and floating-point div, mul.</span></li>
</ul><p><span>These follow the same semantics as the scalar operations, e.g., in terms of what uses exhibit undefined or implementation-defined behavior.</span></p><h1 id="Wording" data-id="Wording"><a class="anchor hidden-xs" href="#Wording" title="Wording"><span class="octicon octicon-link"></span></a><span>Wording</span></h1><p><span>Add feature test macro to </span><code>&lt;version&gt;</code><span> synopsis:</span></p><pre><code class="cpp hljs"><span class="token macro property"><span class="token directive-hash">#</span><span class="token directive keyword">define</span> <span class="token macro-name">__cpp_lib_atomic_fetch_ext</span> <span class="token expression"><span class="token number">202</span>XXXL </span><span class="token comment">// also in &lt;atomic&gt;</span></span>
</code></pre><p><span>Add following functions for </span><code>&lt;op&gt;</code><span> in </span><code>{mod, nand, div, mul}</code><span>, immediately below </span><code>atomic_fetch_xor_explicit</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
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<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token comment">// 33.5.9, non-member functions</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>Add following functions for </span><code>&lt;op&gt;</code><span> in </span><code>{shl, shr}</code><span>, immediately afterwards:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
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<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token comment">// 33.5.9, non-member functions</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>Add following functions immediately afterwards:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
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<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token punctuation">,</span> <span class="token keyword">typename</span> <span class="token class-name">BinaryOp</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> BinaryOp<span class="token operator">&amp;&amp;</span> bop<span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token punctuation">,</span> <span class="token keyword">typename</span> <span class="token class-name">BinaryOp</span><span class="token operator">&gt;</span>
T <span class="token generic-function"><span class="token function">atomic_fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                    <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token punctuation">,</span> <span class="token keyword">typename</span> <span class="token class-name">BinaryOp</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span><span class="token keyword">volatile</span> atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token keyword">template</span><span class="token operator">&lt;</span><span class="token keyword">class</span> <span class="token class-name">T</span><span class="token punctuation">,</span> <span class="token keyword">typename</span> <span class="token class-name">BinaryOp</span><span class="token operator">&gt;</span>
T atomic_fetch_<span class="token operator">&lt;</span>op<span class="token operator">&gt;</span><span class="token function">_explicit</span><span class="token punctuation">(</span>atomic<span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token operator">*</span><span class="token punctuation">,</span> <span class="token comment">// freestanding</span>
                             <span class="token keyword">typename</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>T<span class="token operator">&gt;</span><span class="token double-colon punctuation">::</span>value_type<span class="token punctuation">,</span>
                             memory_order<span class="token punctuation">)</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
</div></div></code></pre><p><span>Modify </span><a href="https://eel.is/c++draft/atomics#tab:atomic.types.int.comp" target="_blank" rel="noopener"><span>tab:atomic.types.int.comp</span></a><span> as follows:</span></p><table>
<thead>
<tr>
<th><span>key</span></th>
<th><span>op</span></th>
<th><span>computation</span></th>
</tr>
</thead>
<tbody>
<tr>
<td><span>add</span></td>
<td><code>+</code></td>
<td><span>addition</span></td>
</tr>
<tr>
<td><span>sub</span></td>
<td><code>-</code></td>
<td><span>subtraction</span></td>
</tr>
<tr>
<td><ins><span>mul</span></ins></td>
<td><code>*</code></td>
<td><ins><span>multiplication</span></ins></td>
</tr>
<tr>
<td><ins><span>div</span></ins></td>
<td><code>/</code></td>
<td><ins><span>division</span></ins></td>
</tr>
<tr>
<td><ins><span>mod</span></ins></td>
<td><code>%</code></td>
<td><ins><span>modulo</span></ins></td>
</tr>
<tr>
<td><span>max</span></td>
<td></td>
<td><span>maximum</span></td>
</tr>
<tr>
<td><span>min</span></td>
<td></td>
<td><span>minimum</span></td>
</tr>
<tr>
<td><span>and</span></td>
<td><code>&amp;</code></td>
<td><span>bitwise and</span></td>
</tr>
<tr>
<td><span>or</span></td>
<td><code>|</code></td>
<td><span>bitwise inclusive or</span></td>
</tr>
<tr>
<td><span>xor</span></td>
<td><code>^</code></td>
<td><span>bitwise exclusive or</span></td>
</tr>
<tr>
<td><ins><span>nand</span></ins></td>
<td></td>
<td><ins><span>bitwise and-not</span></ins></td>
</tr>
<tr>
<td><ins><span>shl</span></ins></td>
<td><code>&lt;&lt;</code></td>
<td><ins><span>left shift</span></ins></td>
</tr>
<tr>
<td><ins><span>shr</span></ins></td>
<td><code>&gt;&gt;</code></td>
<td><ins><span>right shift</span></ins></td>
</tr>
</tbody>
</table><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{mod, nand, div, mul}</code><span>, add following public functions to [atomics.ref.int] specialization, immediately below </span><code>fetch_xor</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic_ref</span><span class="token operator">&lt;</span>integral<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>integral<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>integral<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{shl, shr}</code><span>, add following public functions to [atomics.ref.int] specialization, immediately below </span><code>fetch_xor</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic_ref</span><span class="token operator">&lt;</span>integral<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{mul, div}</code><span>, add following public functions to [atomics.ref.float] specialization, immediately below </span><code>fetch_sub</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic_ref</span><span class="token operator">&lt;</span>floating<span class="token operator">-</span>point<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
floating<span class="token operator">-</span>point <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>floating<span class="token operator">-</span>point<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
floating<span class="token operator">-</span>point <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>floating<span class="token operator">-</span>point<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{mod, nand, div, mul}</code><span>, add following public functions to [atomics.types.int] specialization, immediately below </span><code>fetch_xor</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>integral<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>integral<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>integral<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{shl, shr}</code><span>, add following public functions to [atomics.types.int] specialization, immediately below </span><code>fetch_xor</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>integral<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
integral <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span><span class="token keyword">const</span> <span class="token keyword">unsigned</span><span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre><p><span>For each </span><code>&lt;op&gt;</code><span> in </span><code>{mul, div}</code><span>, add following public functions to [atomics.types.float] specialization, immediately below </span><code>fetch_sub</code><span>:</span></p><pre><code class="cpp hljs"><div class="wrapper"><div class="gutter linenumber"><span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span>
<span></span></div><div class="code"><span class="token keyword">namespace</span> std <span class="token punctuation">{</span>
<span class="token keyword">template</span> <span class="token operator">&lt;</span><span class="token operator">&gt;</span> <span class="token keyword">struct</span> <span class="token class-name">atomic</span><span class="token operator">&lt;</span>floating<span class="token operator">-</span>point<span class="token operator">&gt;</span> <span class="token punctuation">{</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
floating<span class="token operator">-</span>point <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>floating<span class="token operator">-</span>point<span class="token punctuation">,</span> memory_order <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
floating<span class="token operator">-</span>point <span class="token generic-function"><span class="token function">fetch_</span><span class="token generic class-name"><span class="token operator">&lt;</span>op<span class="token operator">&gt;</span></span></span><span class="token punctuation">(</span>floating<span class="token operator">-</span>point<span class="token punctuation">,</span> memory_order success <span class="token operator">=</span> memory_order<span class="token double-colon punctuation">::</span>seq_cst<span class="token punctuation">)</span> <span class="token keyword">const</span> <span class="token keyword">noexcept</span><span class="token punctuation">;</span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</div></div></code></pre></div>
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