General-purpose registers are represented by predefined symbols of the
form ‘rN’, where N represents a number between
0 and 63. However, the following registers have
canonical names that must be used instead:
r54r55r56r57r58r59r60r61r62r63The assembler will emit a warning if a numeric name is used instead of
the non-numeric name. The .no_require_canonical_reg_names
assembler pseudo-op turns off this
warning. .require_canonical_reg_names turns it back on.