Syntax of AMDGPU Assembler Operands and Modifiers — LLVM 7 documentation

# Syntax of AMDGPU Assembler Operands and Modifiers

- Conventions
- Operands
- Modifiers
  - DS Modifiers
    - ds_offset8
    - ds_offset16
    - sw_offset16
    - gds
  - EXP Modifiers
    - done
    - compr
    - vm
  - FLAT Modifiers
    - flat_offset12
    - flat_offset13
    - glc
    - slc
    - tfe
    - nv
  - MIMG Modifiers
    - dmask
    - unorm
    - glc
    - slc
    - r128
    - tfe
    - lwe
    - da
    - d16
    - a16
  - Miscellaneous Modifiers
    - glc
    - slc
    - tfe
    - nv
  - MUBUF/MTBUF Modifiers
    - idxen
    - offen
    - addr64
    - buf_offset12
    - glc
    - slc
    - lds
    - tfe
    - dfmt
    - nfmt
  - SMRD/SMEM Modifiers
    - glc
    - nv
  - VINTRP Modifiers
    - high
  - VOP1/VOP2 DPP Modifiers
    - dpp_ctrl
    - row_mask
    - bank_mask
    - bound_ctrl
  - VOP1/VOP2/VOPC SDWA Modifiers
    - clamp
    - omod
    - dst_sel
    - dst_unused
    - src0_sel
    - src1_sel
  - VOP1/VOP2/VOPC SDWA Operand Modifiers
    - abs
    - neg
    - sext
  - VOP3 Modifiers
    - vop3_op_sel
    - clamp
    - omod
  - VOP3 Operand Modifiers
    - abs
    - neg
  - VOP3P Modifiers
    - op_sel
    - op_sel_hi
    - neg_lo
    - neg_hi
    - clamp
  - VOP3P V_MAD_MIX Modifiers
    - mad_mix_op_sel
    - mad_mix_op_sel_hi
    - abs
    - neg
    - clamp

## Conventions

The following conventions are used in syntax description:

> Notation | Description
> --- | ---
> {0..N} | Any integer value in the range from 0 to N (inclusive). Unless stated otherwise, this value may be specified as either a literal or an llvm expression.
> <x> | Syntax and meaning of <x> is explained elsewhere.

## Operands

TBD

## Modifiers

### DS Modifiers

#### ds_offset8

Specifies an immediate unsigned 8-bit offset, in bytes. The default value is 0.

Used with DS instructions which have 2 addresses.

> Syntax | Description
> --- | ---
> offset:{0..0xFF} | Specifies a 8-bit offset.

#### ds_offset16

Specifies an immediate unsigned 16-bit offset, in bytes. The default value is 0.

Used with DS instructions which have 1 address.

> Syntax | Description
> --- | ---
> offset:{0..0xFFFF} | Specifies a 16-bit offset.

#### sw_offset16

This is a special modifier which may be used with ds_swizzle_b32 instruction only. Specifies a sizzle pattern in numeric or symbolic form. The default value is 0.

See AMD documentation for more information.

> Syntax | Description
> --- | ---
> offset:{0..0xFFFF} | Specifies a 16-bit swizzle pattern in a numeric form.
> offset:swizzle(QUAD_PERM,{0..3},{0..3},{0..3},{0..3}) | Specifies a quad permute mode pattern; each number is a lane id.
> offset:swizzle(BITMASK_PERM, “<mask>”) | Specifies a bitmask permute mode pattern which converts a 5-bit lane id to another lane id with which the lane interacts. <mask> is a 5 character sequence which specifies how to transform the bits of the lane id. The following characters are allowed: “0” - set bit to 0. “1” - set bit to 1. “p” - preserve bit. “i” - inverse bit.
> offset:swizzle(BROADCAST,{2..32},{0..N}) | Specifies a broadcast mode. Broadcasts the value of any particular lane to all lanes in its group. The first numeric parameter is a group size and must be equal to 2, 4, 8, 16 or 32. The second numeric parameter is an index of the lane being broadcasted. The index must not exceed group size.
> offset:swizzle(SWAP,{1..16}) | Specifies a swap mode. Swaps the neighboring groups of 1, 2, 4, 8 or 16 lanes.
> offset:swizzle(REVERSE,{2..32}) | Specifies a reverse mode. Reverses the lanes for groups of 2, 4, 8, 16 or 32 lanes.

#### gds

Specifies whether to use GDS or LDS memory (LDS is the default).

> Syntax | Description
> --- | ---
> gds | Use GDS memory.

### EXP Modifiers

#### done

Specifies if this is the last export from the shader to the target. By default, current instruction does not finish an export sequence.

> Syntax | Description
> --- | ---
> done | Indicates the last export operation.

#### compr

Indicates if the data are compressed (not compressed by default).

> Syntax | Description
> --- | ---
> compr | Data are compressed.

#### vm

Specifies valid mask flag state (off by default).

> Syntax | Description
> --- | ---
> vm | Set valid mask flag.

### FLAT Modifiers

#### flat_offset12

Specifies an immediate unsigned 12-bit offset, in bytes. The default value is 0.

Cannot be used with global/scratch opcodes. GFX9 only.

> Syntax | Description
> --- | ---
> offset:{0..4095} | Specifies a 12-bit unsigned offset.

#### flat_offset13

Specifies an immediate signed 13-bit offset, in bytes. The default value is 0.

Can be used with global/scratch opcodes only. GFX9 only.

> Syntax | Description
> --- | ---
> offset:{-4096..+4095} | Specifies a 13-bit signed offset.

#### glc

See a description here.

#### slc

See a description here.

#### tfe

See a description here.

#### nv

See a description here.

### MIMG Modifiers

#### dmask

Specifies which channels (image components) are used by the operation. By default, no channels are used.

> Syntax | Description
> --- | ---
> dmask:{0..15} | Each bit corresponds to one of 4 image components (RGBA). If the specified bit value is 0, the component is not used, value 1 means that the component is used.

This modifier has some limitations depending on instruction kind:

> Instruction Kind | Valid dmask Values
> --- | ---
> 32-bit atomic cmpswap | 0x3
> other 32-bit atomic instructions | 0x1
> 64-bit atomic cmpswap | 0xF
> other 64-bit atomic instructions | 0x3
> GATHER4 | 0x1, 0x2, 0x4, 0x8
> Other instructions | any value

#### unorm

Specifies whether address is normalized or not (normalized by default).

> Syntax | Description
> --- | ---
> unorm | Force address to be un-normalized.

#### glc

See a description here.

#### slc

See a description here.

#### r128

Specifies texture resource size. The default size is 256 bits.

GFX7 and GFX8 only.

> Syntax | Description
> --- | ---
> r128 | Specifies 128 bits texture resource size.

#### tfe

See a description here.

#### lwe

Specifies LOD warning status (LOD warning is disabled by default).

> Syntax | Description
> --- | ---
> lwe | Enables LOD warning.

#### da

Specifies if an array index must be sent to TA. By default, array index is not sent.

> Syntax | Description
> --- | ---
> da | Send an array-index to TA.

#### d16

Specifies data size: 16 or 32 bits (32 bits by default). Not supported by GFX7.

> Syntax | Description
> --- | ---
> d16 | Enables 16-bits data mode. On loads, convert data in memory to 16-bit format before storing it in VGPRs. For stores, convert 16-bit data in VGPRs to 32 bits before going to memory. Note that 16-bit data are stored in VGPRs unpacked in GFX8.0. In GFX8.1 and GFX9 16-bit data are packed.

#### a16

Specifies size of image address components: 16 or 32 bits (32 bits by default). GFX9 only.

> Syntax | Description
> --- | ---
> a16 | Enables 16-bits image address components.

### Miscellaneous Modifiers

#### glc

This modifier has different meaning for loads, stores, and atomic operations. The default value is off (0).

See AMD documentation for details.

> Syntax | Description
> --- | ---
> glc | Set glc bit to 1.

#### slc

Specifies cache policy. The default value is off (0).

See AMD documentation for details.

> Syntax | Description
> --- | ---
> slc | Set slc bit to 1.

#### tfe

Controls access to partially resident textures. The default value is off (0).

See AMD documentation for details.

> Syntax | Description
> --- | ---
> tfe | Set tfe bit to 1.

#### nv

Specifies if instruction is operating on non-volatile memory. By default, memory is volatile.

GFX9 only.

> Syntax | Description
> --- | ---
> nv | Indicates that instruction operates on non-volatile memory.

### MUBUF/MTBUF Modifiers

#### idxen

Specifies whether address components include an index. By default, no components are used.

Can be used together with offen.

Cannot be used with addr64.

> Syntax | Description
> --- | ---
> idxen | Address components include an index.

#### offen

Specifies whether address components include an offset. By default, no components are used.

Can be used together with idxen.

Cannot be used with addr64.

> Syntax | Description
> --- | ---
> offen | Address components include an offset.

#### addr64

Specifies whether a 64-bit address is used. By default, no address is used.

GFX7 only. Cannot be used with offen and idxen modifiers.

> Syntax | Description
> --- | ---
> addr64 | A 64-bit address is used.

#### buf_offset12

Specifies an immediate unsigned 12-bit offset, in bytes. The default value is 0.

> Syntax | Description
> --- | ---
> offset:{0..0xFFF} | Specifies a 12-bit unsigned offset.

#### glc

See a description here.

#### slc

See a description here.

#### lds

Specifies where to store the result: VGPRs or LDS (VGPRs by default).

> Syntax | Description
> --- | ---
> lds | Store result in LDS.

#### tfe

See a description here.

#### dfmt

TBD

#### nfmt

TBD

### SMRD/SMEM Modifiers

#### glc

See a description here.

#### nv

See a description here.

### VINTRP Modifiers

#### high

Specifies which half of the LDS word to use. Low half of LDS word is used by default. GFX9 only.

> Syntax | Description
> --- | ---
> high | Use high half of LDS word.

### VOP1/VOP2 DPP Modifiers

GFX8 and GFX9 only.

#### dpp_ctrl

Specifies how data are shared between threads. This is a mandatory modifier. There is no default value.

Note. The lanes of a wavefront are organized in four banks and four rows.

> Syntax | Description
> --- | ---
> quad_perm:[{0..3},{0..3},{0..3},{0..3}] | Full permute of 4 threads.
> row_mirror | Mirror threads within row.
> row_half_mirror | Mirror threads within 1/2 row (8 threads).
> row_bcast:15 | Broadcast 15th thread of each row to next row.
> row_bcast:31 | Broadcast thread 31 to rows 2 and 3.
> wave_shl:1 | Wavefront left shift by 1 thread.
> wave_rol:1 | Wavefront left rotate by 1 thread.
> wave_shr:1 | Wavefront right shift by 1 thread.
> wave_ror:1 | Wavefront right rotate by 1 thread.
> row_shl:{1..15} | Row shift left by 1-15 threads.
> row_shr:{1..15} | Row shift right by 1-15 threads.
> row_ror:{1..15} | Row rotate right by 1-15 threads.

#### row_mask

Controls which rows are enabled for data sharing. By default, all rows are enabled.

Note. The lanes of a wavefront are organized in four banks and four rows.

> Syntax | Description
> --- | ---
> row_mask:{0..15} | Each of 4 bits in the mask controls one row (0 - disabled, 1 - enabled).

#### bank_mask

Controls which banks are enabled for data sharing. By default, all banks are enabled.

Note. The lanes of a wavefront are organized in four banks and four rows.

> Syntax | Description
> --- | ---
> bank_mask:{0..15} | Each of 4 bits in the mask controls one bank (0 - disabled, 1 - enabled).

#### bound_ctrl

Controls data sharing when accessing an invalid lane. By default, data sharing with invalid lanes is disabled.

> Syntax | Description
> --- | ---
> bound_ctrl:0 | Enables data sharing with invalid lanes. Accessing data from an invalid lane will return zero.

### VOP1/VOP2/VOPC SDWA Modifiers

GFX8 and GFX9 only.

#### clamp

See a description here.

#### omod

See a description here.

GFX9 only.

#### dst_sel

Selects which bits in the destination are affected. By default, all bits are affected.

> Syntax | Description
> --- | ---
> dst_sel:DWORD | Use bits 31:0.
> dst_sel:BYTE_0 | Use bits 7:0.
> dst_sel:BYTE_1 | Use bits 15:8.
> dst_sel:BYTE_2 | Use bits 23:16.
> dst_sel:BYTE_3 | Use bits 31:24.
> dst_sel:WORD_0 | Use bits 15:0.
> dst_sel:WORD_1 | Use bits 31:16.

#### dst_unused

Controls what to do with the bits in the destination which are not selected by dst_sel. By default, unused bits are preserved.

> Syntax | Description
> --- | ---
> dst_unused:UNUSED_PAD | Pad with zeros.
> dst_unused:UNUSED_SEXT | Sign-extend upper bits, zero lower bits.
> dst_unused:UNUSED_PRESERVE | Preserve bits.

#### src0_sel

Controls which bits in the src0 are used. By default, all bits are used.

> Syntax | Description
> --- | ---
> src0_sel:DWORD | Use bits 31:0.
> src0_sel:BYTE_0 | Use bits 7:0.
> src0_sel:BYTE_1 | Use bits 15:8.
> src0_sel:BYTE_2 | Use bits 23:16.
> src0_sel:BYTE_3 | Use bits 31:24.
> src0_sel:WORD_0 | Use bits 15:0.
> src0_sel:WORD_1 | Use bits 31:16.

#### src1_sel

Controls which bits in the src1 are used. By default, all bits are used.

> Syntax | Description
> --- | ---
> src1_sel:DWORD | Use bits 31:0.
> src1_sel:BYTE_0 | Use bits 7:0.
> src1_sel:BYTE_1 | Use bits 15:8.
> src1_sel:BYTE_2 | Use bits 23:16.
> src1_sel:BYTE_3 | Use bits 31:24.
> src1_sel:WORD_0 | Use bits 15:0.
> src1_sel:WORD_1 | Use bits 31:16.

### VOP1/VOP2/VOPC SDWA Operand Modifiers

Operand modifiers are not used separately. They are applied to source operands.

GFX8 and GFX9 only.

#### abs

See a description here.

#### neg

See a description here.

#### sext

Sign-extends value of a (sub-dword) operand to fill all 32 bits. Has no effect for 32-bit operands.

Valid for integer operands only.

> Syntax | Description
> --- | ---
> sext(<operand>) | Sign-extend operand value.

### VOP3 Modifiers

#### vop3_op_sel

Selects the low [15:0] or high [31:16] operand bits for source and destination operands. By default, low bits are used for all operands.

The number of values specified with the op_sel modifier must match the number of instruction operands (both source and destination). First value controls src0, second value controls src1 and so on, except that the last value controls destination. The value 0 selects the low bits, while 1 selects the high bits.

Note. op_sel modifier affects 16-bit operands only. For 32-bit operands the value specified by op_sel must be 0.

GFX9 only.

> Syntax | Description
> --- | ---
> op_sel:[{0..1},{0..1}] | Select operand bits for instructions with 1 source operand.
> op_sel:[{0..1},{0..1},{0..1}] | Select operand bits for instructions with 2 source operands.
> op_sel:[{0..1},{0..1},{0..1},{0..1}] | Select operand bits for instructions with 3 source operands.

#### clamp

Clamp meaning depends on instruction.

For v_cmp instructions, clamp modifier indicates that the compare signals if a floating point exception occurs. By default, signaling is disabled. Not supported by GFX7.

For integer operations, clamp modifier indicates that the result must be clamped to the largest and smallest representable value. By default, there is no clamping. Integer clamping is not supported by GFX7.

For floating point operations, clamp modifier indicates that the result must be clamped to the range [0.0, 1.0]. By default, there is no clamping.

Note. Clamp modifier is applied after output modifiers (if any).

> Syntax | Description
> --- | ---
> clamp | Enables clamping (or signaling).

#### omod

Specifies if an output modifier must be applied to the result. By default, no output modifiers are applied.

Note. Output modifiers are applied before clamping (if any).

Output modifiers are valid for f32 and f64 floating point results only. They must not be used with f16.

Note. v_cvt_f16_f32 is an exception. This instruction produces f16 result but accepts output modifiers.

> Syntax | Description
> --- | ---
> mul:2 | Multiply the result by 2.
> mul:4 | Multiply the result by 4.
> div:2 | Multiply the result by 0.5.

### VOP3 Operand Modifiers

Operand modifiers are not used separately. They are applied to source operands.

#### abs

Computes absolute value of its operand. Applied before neg (if any). Valid for floating point operands only.

> Syntax | Description
> --- | ---
> abs(<operand>) | Get absolute value of operand.
> |<operand>| | The same as above.

#### neg

Computes negative value of its operand. Applied after abs (if any). Valid for floating point operands only.

> Syntax | Description
> --- | ---
> neg(<operand>) | Get negative value of operand.
> -<operand> | The same as above.

### VOP3P Modifiers

This section describes modifiers of regular VOP3P instructions. v_mad_mix modifiers are described in a separate section.

GFX9 only.

#### op_sel

Selects the low [15:0] or high [31:16] operand bits as input to the operation which results in the lower-half of the destination. By default, low bits are used for all operands.

The number of values specified with the op_sel modifier must match the number of source operands. First value controls src0, second value controls src1 and so on. The value 0 selects the low bits, while 1 selects the high bits.

> Syntax | Description
> --- | ---
> op_sel:[{0..1}] | Select operand bits for instructions with 1 source operand.
> op_sel:[{0..1},{0..1}] | Select operand bits for instructions with 2 source operands.
> op_sel:[{0..1},{0..1},{0..1}] | Select operand bits for instructions with 3 source operands.

#### op_sel_hi

Selects the low [15:0] or high [31:16] operand bits as input to the operation which results in the upper-half of the destination. By default, high bits are used for all operands.

The number of values specified with the op_sel_hi modifier must match the number of source operands. First value controls src0, second value controls src1 and so on. The value 0 selects the low bits, while 1 selects the high bits.

> Syntax | Description
> --- | ---
> op_sel_hi:[{0..1}] | Select operand bits for instructions with 1 source operand.
> op_sel_hi:[{0..1},{0..1}] | Select operand bits for instructions with 2 source operands.
> op_sel_hi:[{0..1},{0..1},{0..1}] | Select operand bits for instructions with 3 source operands.

#### neg_lo

Specifies whether to change sign of operand values selected by op_sel. These values are then used as input to the operation which results in the upper-half of the destination.

The number of values specified with this modifier must match the number of source operands. First value controls src0, second value controls src1 and so on.

The value 0 indicates that the corresponding operand value is used unmodified, the value 1 indicates that negative value of the operand must be used.

By default, operand values are used unmodified.

This modifier is valid for floating point operands only.

> Syntax | Description
> --- | ---
> neg_lo:[{0..1}] | Select affected operands for instructions with 1 source operand.
> neg_lo:[{0..1},{0..1}] | Select affected operands for instructions with 2 source operands.
> neg_lo:[{0..1},{0..1},{0..1}] | Select affected operands for instructions with 3 source operands.

#### neg_hi

Specifies whether to change sign of operand values selected by op_sel_hi. These values are then used as input to the operation which results in the upper-half of the destination.

The number of values specified with this modifier must match the number of source operands. First value controls src0, second value controls src1 and so on.

The value 0 indicates that the corresponding operand value is used unmodified, the value 1 indicates that negative value of the operand must be used.

By default, operand values are used unmodified.

This modifier is valid for floating point operands only.

> Syntax | Description
> --- | ---
> neg_hi:[{0..1}] | Select affected operands for instructions with 1 source operand.
> neg_hi:[{0..1},{0..1}] | Select affected operands for instructions with 2 source operands.
> neg_hi:[{0..1},{0..1},{0..1}] | Select affected operands for instructions with 3 source operands.

#### clamp

See a description here.

### VOP3P V_MAD_MIX Modifiers

These instructions use VOP3P format but have different modifiers.

GFX9 only.

#### mad_mix_op_sel

This operand has meaning only for 16-bit source operands as indicated by mad_mix_op_sel_hi. It specifies to select either the low [15:0] or high [31:16] operand bits as input to the operation.

The value 0 indicates the low bits, the value 1 indicates the high 16 bits. By default, low bits are used for all operands.

> Syntax | Description
> --- | ---
> op_sel:[{0..1},{0..1},{0..1}] | Select location of each 16-bit source operand.

#### mad_mix_op_sel_hi

Selects the size of source operands: either 32 bits or 16 bits. By default, 32 bits are used for all source operands.

The value 0 indicates 32 bits, the value 1 indicates 16 bits. The location of 16 bits in the operand may be specified by mad_mix_op_sel.

> Syntax | Description
> --- | ---
> op_sel_hi:[{0..1},{0..1},{0..1}] | Select size of each source operand.

#### abs

See a description here.

#### neg

See a description here.

#### clamp

See a description here.