(The meaning of the offset—offset from the frame pointer—distinct
from its use with <code>SB</code>, where it is an offset from the symbol.)
The assembler enforces this convention, rejecting plain <code>0(FP)</code> and <code>8(FP)</code>.
The actual name is semantically irrelevant but should be used to document
the argument's name.
It is worth stressing that <code>FP</code> is always a
pseudo-register, not a hardware