# AMDGPU Instructions Notation

- Introduction

- Instructions

  - Notation

- Opcode

  - Notation

- Operands

  - Notation

    - Operand Kinds

    - Operand Tags

- Modifiers

  - Notation

## Introduction

This is an overview of notation used to describe syntax of AMDGPU assembler instructions.

This notation mimics the syntax of assembler instructions except that instead of real operands and modifiers it provides references to their description.

## Instructions

### Notation

This is the notation used to describe AMDGPU instructions:

> `<`opcode description`> <`operands description`> <`modifiers description`>`

## Opcode

### Notation

TBD

## Operands

An instruction may have zero or more operands. They are comma-separated in the description:

> `<`description of operand 0`>, <`description of operand 1`>, ...`

The order of operands is fixed. Operands cannot be omitted except for special cases described below.

### Notation

An operand is described using the following notation:

> <kind><name><tag0><tag1>…

Where:

- kind is an optional prefix describing operand kind.

- name is a link to a description of the operand.

- tags are optional. They are used to indicate special operand properties.

#### Operand Kinds

Operand kind indicates which values are accepted by the operand.

- Operands which only accept vector registers are labelled with ‘v’ prefix.

- Operands which only accept scalar values are labelled with ‘s’ prefix.

- Operands which accept both vector registers and scalar values have no prefix.

Examples:

    vdata          // operand only accepts vector registers
    sdst           // operand only accepts scalar registers
    src1           // operand accepts both scalar and vector registers

#### Operand Tags

Operand tags indicate special operand properties.

> Operand tag | Meaning
> --- | ---
> :opt | An optional operand.
> :m | An operand which may be used with VOP3 operand modifiers or SDWA operand modifiers.
> :dst | An input operand which may also serve as a destination if glc modifier is specified.
> :fx | This is an f32 or f16 operand depending on m_op_sel_hi modifier.
> :<type> | Operand type differs from type implied by the opcode name. This tag specifies actual operand type.

Examples:

    src1:m             // src1 operand may be used with operand modifiers
    vdata:dst          // vdata operand may be used as both source and destination
    vdst:u32           // vdst operand has u32 type

## Modifiers

An instruction may have zero or more optional modifiers. They are space-separated in the description:

> `<`description of modifier 0`> <`description of modifier 1`> ...`

The order of modifiers is fixed.

### Notation

A modifier is described using the following notation:

> <name>

Where name is a link to a description of the modifier.