Chapter 30. MMIX Dependent Features

177

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

(Section 4.6.1.1 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

(Section 8.7

.byte expressions

). 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 respec 

tively. Before anything else happens for the directive, the current location is aligned to the re 

spective constant size boundary. 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 (Section 4.6.1.1 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, Section 30.3.2 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.