<i>W</i>(<i>r</i>) must be a write <i>w</i> that is <i>visible</i> to <i>r</i>,
where visible means that both of the following hold:
</p>

<ol>
	<li><i>w</i> happens before <i>r</i>.</li>
	<li><i>w</i> does not happen before any other write <i>w'</i> (to <i>x</i>) that happens before <i>r</i>.</li>
</ol>

<p>
A <i>read-write data race</i> on memory location <i>x</i>
consists of a read-like memory operation <i>r</i> on <i>x</i>

order.
</p>

<p>
For example, in the (function-local) assignment
</p>
<pre>
y[f()], ok = g(h(), i()+x[j()], &lt;-c), k()
</pre>
<p>
the function calls and communication happen in the order
<code>f()</code>, <code>h()</code>, <code>i()</code>, <code>j()</code>,
<code>&lt;-c</code>, <code>g()</code>, and <code>k()</code>.
However, the order of those events compared to the evaluation

</li>

<li>
<code>(R5, R6)</code>: Destination register pair.
</li>

</ul>

<h3 id="arm64">ARM64</h3>

<p>
<code>R18</code> is the "platform register", reserved on the Apple platform.
To prevent accidental misuse, the register is named <code>R18_PLATFORM</code>.
<code>R27</code> and <code>R28</code> are reserved by the compiler and linker.
<code>R29</code> is the frame pointer.

</p>

<p>
For example, in the (function-local) assignment
</p>
<pre>
y[f()], ok = g(z || h(), i()+x[j()], &lt;-c), k()
</pre>
<p>
the function calls and communication happen in the order
<code>f()</code>, <code>h()</code> (if <code>z</code>
evaluates to false), <code>i()</code>, <code>j()</code>,
<code>&lt;-c</code>, <code>g()</code>, and <code>k()</code>.