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