12.23 DN and SN

The DN and SN directives define names for VFP registers.


name directive expr{.type}
is the name to be assigned to the extension register. name cannot be the same as any of the predefined names.
is DN or SN.
Can be:
  • An expression that evaluates to a number in the range:
    • 0-15 if you are using DN in VFPv2.
    • 0-31 otherwise.
  • A predefined register name, or a register name that has already been defined in a previous directive.
is any VFP datatype.
type is Extended notation.


Use DN or SN to allocate convenient names to extension registers, to help you to remember what you use each one for.
The DN directive defines a name for a specified 64-bit extension register.
The SN directive defines a name for a specified single-precision VFP register.


Avoid conflicting uses of the same register under different names.
You cannot specify a vector length in a DN or SN directive.


energy  DN  6   ; defines energy as a symbol for VFP double-precision register 6
mass    SN  16  ; defines mass as a symbol for VFP single-precision register 16
Related concepts
8.9 VFP data types
8.22 Overview of VFP directives and vector notation
8.10 Extended notation extension for VFP
Related reference
2.10 Predeclared core register names
2.11 Predeclared extension register names
2.12 Predeclared coprocessor names
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