The assembler uses them to hold temporary values when assembling some instructions.
</p>

<p>
<code>R13</code> points to the <code>g</code> (goroutine) structure.
This register must be referred to as <code>g</code>; the name <code>R13</code> is not recognized.
</p>

<p>
<code>R15</code> points to the stack frame and should typically only be accessed using the