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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 |