Chapter 40. VAX Dependent Features

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.gfloat

This expects zero or more flonums, separated by commas, and assembles Vax

g

format 64 bit

floating point constants.

.hfloat

This expects zero or more flonums, separated by commas, and assembles Vax

h

format 128 bit

floating point constants.

40.4. VAX Opcodes

All DEC mnemonics are supported. Beware that

case...

instructions have exactly 3 operands. The

dispatch table that follows the

case...

instruction should be made with

.word

statements. This is

compatible with all unix assemblers we know of.

40.5. VAX Branch Improvement

Certain pseudo opcodes are permitted. They are for branch instructions. They expand to the shortest

branch instruction that reaches the target. Generally these mnemonics are made by substituting

j

for

b

at the start of a DEC mnemonic. This feature is included both for compatibility and to help compilers.

If you do not need this feature, avoid these opcodes. Here are the mnemonics, and the code they can

expand into.

jbsb

Jsb

is already an instruction mnemonic, so we chose

jbsb

.

(byte displacement)

bsbb ...

(word displacement)

bsbw ...

(long displacement)

jsb ...

jbr

jr

Unconditional branch.

(byte displacement)

brb ...

(word displacement)

brw ...

(long displacement)

jmp ...