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(as.info)MMIX-Pseudos

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Assembler Directives
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`LOC'
     The `LOC' directive sets the current location to the value of the
     operand field, which may include changing sections.  If the
     operand is a constant, the section is set to either `.data' if the
     value is `0x2000000000000000' or larger, else it is set to `.text'.
     Within a section, the current location may only be changed to
     monotonically higher addresses.  A LOC expression must be a
     previously defined symbol or a "pure" constant.

     An example, which sets the label PREV to the current location, and
     updates the current location to eight bytes forward:
          prev LOC @+8

     When a LOC has a constant as its operand, a symbol
     `__.MMIX.start..text' or `__.MMIX.start..data' is defined
     depending on the address as mentioned above.  Each such symbol is
     interpreted as special by the linker, locating the section at that
     address.  Note that if multiple files are linked, the first object
     file with that section will be mapped to that address (not
     necessarily the file with the LOC definition).

`LOCAL'
     Example:
           LOCAL external_symbol
           LOCAL 42
           .local asymbol

     This directive-operation generates a link-time assertion that the
     operand does not correspond to a global register.  The operand is
     an expression that at link-time resolves to a register symbol or a
     number.  A number is treated as the register having that number.
     There is one restriction on the use of this directive: the
     pseudo-directive must be placed in a section with contents, code
     or data.

`IS'
     The `IS' directive:
          asymbol IS an_expression
     sets the symbol `asymbol' to `an_expression'.  A symbol may not be
     set more than once using this directive.  Local labels may be set
     using this directive, for example:
          5H IS @+4

`GREG'
     This directive reserves a global register, gives it an initial
     value and optionally gives it a symbolic name.  Some examples:

          areg GREG
          breg GREG data_value
               GREG data_buffer
               .greg creg, another_data_value

     The symbolic register name can be used in place of a (non-special)
     register.  If a value isn't provided, it defaults to zero.  Unless
     the option `--no-merge-gregs' is specified, non-zero registers
     allocated with this directive may be eliminated by `as'; another
     register with the same value used in its place.  Any of the
     instructions `CSWAP', `GO', `LDA', `LDBU', `LDB', `LDHT', `LDOU',
     `LDO', `LDSF', `LDTU', `LDT', `LDUNC', `LDVTS', `LDWU', `LDW',
     `PREGO', `PRELD', `PREST', `PUSHGO', `STBU', `STB', `STCO', `STHT',
     `STOU', `STSF', `STTU', `STT', `STUNC', `SYNCD', `SYNCID', can
     have a value nearby an initial value in place of its second and
     third operands.  Here, "nearby" is defined as within the range
     0...255 from the initial value of such an allocated register.

          buffer1 BYTE 0,0,0,0,0
          buffer2 BYTE 0,0,0,0,0
           ...
           GREG buffer1
           LDOU $42,buffer2
     In the example above, the `Y' field of the `LDOUI' instruction
     (LDOU with a constant Z) will be replaced with the global register
     allocated for `buffer1', and the `Z' field will have the value 5,
     the offset from `buffer1' to `buffer2'.  The result is equivalent
     to this code:
          buffer1 BYTE 0,0,0,0,0
          buffer2 BYTE 0,0,0,0,0
           ...
          tmpreg GREG buffer1
           LDOU $42,tmpreg,(buffer2-buffer1)

     Global registers allocated with this directive are allocated in
     order higher-to-lower within a file.  Other than that, the exact
     order of register allocation and elimination is undefined.  For
     example, the order is undefined when more than one file with such
     directives are linked together.  With the options `-x' and
     `--linker-allocated-gregs', `GREG' directives for two-operand
     cases like the one mentioned above can be omitted.  Sufficient
     global registers will then be allocated by the linker.

`BYTE'
     The `BYTE' directive takes a series of operands separated by a
     comma.  If an operand is a string (Note: Strings), each
     character of that string is emitted as a byte.  Other operands
     must be constant expressions without forward references, in the
     range 0...255.  If you need operands having expressions with
     forward references, use `.byte' (Note: Byte).  An operand can be
     omitted, defaulting to a zero value.

`WYDE'
`TETRA'
`OCTA'
     The directives `WYDE', `TETRA' and `OCTA' emit constants of two,
     four and eight bytes size respectively.  Before anything else
     happens for the directive, the current location is aligned to the
     respective constant-size bondary.  If a label is defined at the
     beginning of the line, its value will be that after the alignment.
     A single operand can be omitted, defaulting to a zero value
     emitted for the directive.  Operands can be expressed as strings
     (Note: Strings), in which case each character in the string is
     emitted as a separate constant of the size indicated by the
     directive.

`PREFIX'
     The `PREFIX' directive sets a symbol name prefix to be prepended to
     all symbols (except local symbols, Note: MMIX-Symbols), that are
     not prefixed with `:', until the next `PREFIX' directive.  Such
     prefixes accumulate.  For example,
           PREFIX a
           PREFIX b
          c IS 0
     defines a symbol `abc' with the value 0.

`BSPEC'
`ESPEC'
     A pair of `BSPEC' and `ESPEC' directives delimit a section of
     special contents (without specified semantics).  Example:
           BSPEC 42
           TETRA 1,2,3
           ESPEC
     The single operand to `BSPEC' must be number in the range 0...255.
     The `BSPEC' number 80 is used by the GNU binutils implementation.