<p>
That is, the compiler must not rewrite the program into this one:
</p>

<pre>
*p = 2
if !cond {
	*p = 1
}
</pre>

<p>
If <code>cond</code> is false and another goroutine is reading <code>*p</code>,
then in the original program, the other goroutine can only observe any prior value of <code>*p</code> and <code>1</code>.