76

Chapter 11. Alpha Dependent Features

 F

 32addr

These options are ignored for backward compatibility.

11.3. Syntax

The assembler syntax closely follow the Alpha Reference Manual; assembler directives and general

syntax closely follow the OSF/1 and OpenVMS syntax, with a few differences for ELF.

11.3.1. Special Characters

#

is the line comment character.

;

can be used instead of a newline to separate statements.

11.3.2. Register Names

The 32 integer registers are referred to as

$n

or

$rn

. In addition, registers 15, 28, 29, and 30 may be

referred to by the symbols

$fp

,

$at

,

$gp

, and

$sp

respectively.

The 32 floating point registers are referred to as

$fn

.

11.3.3. Relocations

Some of these relocations are available for ECOFF, but mostly only for ELF. They are modeled after

the relocation format introduced in Digital Unix 4.0, but there are additions.

The format is

!tag

or

!tag!number

where

tag

is the name of the relocation. In some cases

number

is used to relate specific instructions.

The relocation is placed at the end of the instruction like so:

ldah

$0,a($29)

!gprelhigh

lda

$0,a($0)

!gprellow

ldq

$1,b($29)

!literal!100

ldl

$2,0($1)

!lituse_base!100

!literal

!literal!N

Used with an

ldq

instruction to load the address of a symbol from the GOT.

A sequence number

N

is optional, and if present is used to pair

lituse

relocations with this

literal

relocation. The

lituse

relocations are used by the linker to optimize the code based

on the final location of the symbol.

Note that these optimizations are dependent on the data flow of the program. Therefore, if any

lituse

is paired with a

literal

relocation, then all uses of the register set by the

literal

instruction must also be marked with

lituse

relocations. This is because the original

literal

instruction may be deleted or transformed into another instruction.

Also note that there may be a one to many relationship between

literal

and

lituse

, but not

a many to one. That is, if there are two code paths that load up the same address and feed the

value to a single use, then the use may not use a

lituse

relocation.