s390 Register - Using as

9.30.3.1 Register naming

The as recognizes a number of predefined symbols for the various processor registers. A register specification in one of the instruction formats is an unsigned integer between 0 and 15. The specific instruction and the position of the register in the instruction format denotes the type of the register. The register symbols are prefixed with `%':

     %rN the 16 general purpose registers, 0 <= N <= 15
     
%fN the 16 floating point registers, 0 <= N <= 15
     
%aN the 16 access registers, 0 <= N <= 15
     
%cN the 16 control registers, 0 <= N <= 15
     
%lit an alias for the general purpose register %r13
     
%sp an alias for the general purpose register %r15

%rN	the 16 general purpose registers, 0 <= N <= 15
%fN	the 16 floating point registers, 0 <= N <= 15
%aN	the 16 access registers, 0 <= N <= 15
%cN	the 16 control registers, 0 <= N <= 15
%lit	an alias for the general purpose register %r13
%sp	an alias for the general purpose register %r15