124
Chapter 20. ESA/390 Dependent Features
AH r0,=H'42'
ME r6,=E'3.1416'
MD r6,=D'3.14159265358979'
O r6,=XL4'cacad0d0'
.ltorg
should all behave as expected: that is, an entry in the literal pool will be created (or reused if it already
exists), and the instruction operands will be the displacement into the literal pool using the current
base register (as last declared with the
.using
directive).
20.4. Floating Point
The assembler generates only ieee floating point numbers. The older floating point formats are not
supported.
20.5. ESA/390 Assembler Directives
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 imple 
ment the ESA/390 addressing model. The most important of these are
.using
and
.ltorg
These are the additional directives in
as
for the ESA/390:
.dc
A small subset of the usual DC directive is supported.
.drop regno
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.
.ebcdic string
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.
EQU
The standard HLASM style EQU directive is not supported; however, the standard
as
directive
.equ can be used to the same effect.
.ltorg
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.
.using expr,regno
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 (typically, the
.data
section). This feature allows dynami 
cally loaded objects to be implemented in a relatively straightforward way. A
.using
directive
must always be specified in the
.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






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