The 128 integer registers are referred to as rn. The 128 floating-point registers are referred to as fn. The 128 application registers are referred to as arn. The 128 control registers are referred to as crn. The 64 one-bit predicate registers are referred to as pn. The 8 branch registers are referred to as bn. In addition, the assembler defines a number of aliases: gp (r1), sp (r12), rp (b0), ret0 (r8), ret1 (r9), ret2 (r10), ret3 (r9), fargn (f8+n), and fretn (f8+n).
For convenience, the assembler also defines aliases for all named application and control registers. For example, ar.bsp refers to the register backing store pointer (ar17). Similarly, cr.eoi refers to the end-of-interrupt register (cr67).