e> on entry.
</p>

<p>
The name <code>SP</code> always refers to the virtual stack pointer described earlier.
For the hardware register, use <code>R13</code>.
</p>

<h3 id="unsupported_opcodes">Unsupported opcodes</h3>

<p>
The assemblers are designed to support the compiler so not all hardware instructions
are defined for all architectures: if the compiler doesn't generate it, it might not be there.
If you need to use a missing instruction, there are two ways to proceed.
One is to update the assembler to s