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8.10.2 Syntax

This syntax for the Motorola 680x0 was developed at MIT.

The 680x0 version of as uses instructions names and syntax compatible with the Sun assembler. Intervening periods are ignored; for example, `movl' is equivalent to `mov.l'.

In the following table apc stands for any of the address registers (`%a0' through `%a7'), the program counter (`%pc'), the zero-address relative to the program counter (`%zpc'), a suppressed address register (`%za0' through `%za7'), or it may be omitted entirely. The use of size means one of `w' or `l', and it may be omitted, along with the leading colon, unless a scale is also specified. The use of scale means one of `1', `2', `4', or `8', and it may always be omitted along with the leading colon.

The following addressing modes are understood:

Immediate

`#number'

Data Register

`%d0' through `%d7'

Address Register

`%a0' through `%a7'
`%a7' is also known as `%sp', i.e. the Stack Pointer. %a6 is also known as `%fp', the Frame Pointer.

Address Register Indirect

`%a0@' through `%a7@'

Address Register Postincrement

`%a0@+' through `%a7@+'

Address Register Predecrement

`%a0@-' through `%a7@-'

Indirect Plus Offset

`apc@(number)'

Index

`apc@(number,register:size:scale)'

The number may be omitted.

Postindex

`apc@(number)@(onumber,register:size:scale)'

The onumber or the register, but not both, may be omitted.

Preindex

`apc@(number,register:size:scale)@(onumber)'

The number may be omitted. Omitting the register produces the Postindex addressing mode.

Absolute

`symbol', or `digits', optionally followed by `:b', `:w', or `:l'.