as for the ESA/390 supports all of the standard ELF/SVR4
assembler directives that are documented in the main part of this
documentation. Several additional directives are supported in order
to implement the ESA/390 addressing model. The most important of these
These are the additional directives in
as for the ESA/390:
A small subset of the usual DC directive is supported.
Stop using regno as the base register. The regno must
have been previously declared with a
.using directive in the
same section as the current section.
Emit the EBCDIC equivalent of the indicated string. The emitted string
will be null terminated. Note that the directives
.string etc. emit
ascii strings by default.
The standard HLASM-style EQU directive is not supported; however, the
as directive .equ can be used to the same effect.
Dump the literal pool accumulated so far; begin a new literal pool.
The literal pool will be written in the current section; in order to
generate correct assembly, a
.using must have been previously
specified in the same section.
Use regno as the base register for all subsequent RX, RS, and SS form instructions. The expr will be evaluated to obtain the base address; usually, expr will merely be ‘*’.
This assembler allows two
.using directives to be simultaneously
outstanding, one in the
.text section, and one in another section
.data section). This feature allows
dynamically loaded objects to be implemented in a relatively
straightforward way. A
.using directive must always be specified
.text section; this will specify the base register that
will be used for branches in the
.text section. A second
.using may be specified in another section; this will specify
the base register that is used for non-label address literals.
When a second
.using is specified, then the subsequent
.ltorg must be put in the same section; otherwise an error will
Thus, for example, the following code uses
r3 to address branch
r4 to address the literal pool, which has been written
.data section. The is, the constants
=E'3.1416' will all appear in the
.data .using LITPOOL,r4 .text BASR r3,0 .using *,r3 B START .long LITPOOL START: L r4,4(,r3) L r15,=A(some_routine) LTR r15,r15 BNE LABEL AH r0,=H'42' LABEL: ME r6,=E'3.1416' .data LITPOOL: .ltorg
Note that this dual-
.using directive semantics extends
and is not compatible with HLASM semantics. Note that this assembler
directive does not support the full range of HLASM semantics.