as: s390 Register

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1 9.40.3.1 Register naming
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1 The 'as' recognizes a number of predefined symbols for the various
1 processor registers.  A register specification in one of the instruction
1 formats is an unsigned integer between 0 and 15.  The specific
1 instruction and the position of the register in the instruction format
1 denotes the type of the register.  The register symbols are prefixed
1 with '%':
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1      %rN   the 16 general purpose registers, 0 <= N <= 15
1      %fN   the 16 floating point registers, 0 <= N <= 15
1      %aN   the 16 access registers, 0 <= N <= 15
1      %cN   the 16 control registers, 0 <= N <= 15
1      %lit  an alias for the general purpose register %r13
1      %sp   an alias for the general purpose register %r15
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