Chapter 20.

ESA/390 Dependent Features

20.1. Notes

The ESA/390

as

port is currently intended to be a back end for the gnu cc compiler. It is not HLASM

compatible, although it does support a subset of some of the HLASM directives. The only supported

binary file format is ELF; none of the usual MVS/VM/OE/USS object file formats, such as ESD or

XSD, are supported.

When used with the gnu cc compiler, the ESA/390

as

will produce correct, fully relocated, functional

binaries, and has been used to compile and execute large projects. However, many aspects should still

be considered experimental; these include shared library support, dynamically loadable objects, and

any relocation other than the 31 bit relocation.

20.2. Options

as

has no machine dependent command line options for the ESA/390.

20.3. Syntax

The opcode/operand syntax follows the ESA/390 Principles of Operation manual; assembler direc 

tives and general syntax are loosely based on the prevailing AT&T/SVR4/ELF/Solaris style notation.

HLASM style directives are not supported for the most part, with the exception of those described

herein.

A leading dot in front of directives is optional, and the case of directives is ignored; thus for example,

.using and USING have the same effect.

A colon may immediately follow a label definition. This is simply for compatibility with how most

assembly language programmers write code.

#

is the line comment character.

;

can be used instead of a newline to separate statements.

Since

$

has no special meaning, you may use it in symbol names.

Registers can be given the symbolic names r0..r15, fp0, fp2, fp4, fp6. By using thesse symbolic names,

as

can detect simple syntax errors. The name rarg or r.arg is a synonym for r11, rtca or r.tca for r12,

sp, r.sp, dsa r.dsa for r13, lr or r.lr for r14, rbase or r.base for r3 and rpgt or r.pgt for r4.

*

is the current location counter. Unlike

.

it is always relative to the last USING directive. Note that

this means that expressions cannot use multiplication, as any occurrence of

*

will be interpreted as a

location counter.

All labels are relative to the last USING. Thus, branches to a label always imply the use of

base+displacement.

Many of the usual forms of address constants / address literals are supported. Thus,

.using *,r3

L r15,=A(some_routine)

LM r6,r7,=V(some_longlong_extern)

A r1,=F'12'