v_ashr_pk_u8_i32 GPU Native ISA AMD Vector

Vector Arithmetic

v_ashr_pk_u8_i32

Given two signed 32-bit integers and a shift count, calculate the arithmetic shift right (preserving sign bit) of the two integers, saturate the two…

Encoding

Binary Layout (AMD CDNA 5)
NEG
63:61
OMOD
60:59
SRC2
58:50
SRC1
49:41
SRC0
40:32
110101
31:26
1010010001
25:16
CLAMP
15
OPSEL
14:11
ABS
10:8
VDST
7:0
 

The ENC_VOP3 layout from AMD's machine-readable ISA specification (AMD CDNA 5). Opcode 657 in OP rebuilds 0x00000000D6910000, an identifier AMD lists for this encoding. Not the same in every generation: AMD CDNA 4 (opcode 614, field layout).

Format VOP3
Width 64 bits
Opcode 657
Identifier 0x00000000D6910000

Operands

  • VDST
    Written. Operand must be a vector GPR. Uses an 8-bit operand field. Data format: Unsigned 8-bit integral data. Packed 2-component value. (OPR_VGPR, FMT_NUM_PK2_U8)
  • SRC0
    Read. All operands. Covers all operands that are allowed as scalar or vector sources. Data format: Signed 32-bit integral data. (OPR_SRC, FMT_NUM_I32)
  • SRC1
    Read. All operands. Covers all operands that are allowed as scalar or vector sources. Data format: Signed 32-bit integral data. (OPR_SRC, FMT_NUM_I32)
  • SRC2
    Read. All operands. Covers all operands that are allowed as scalar or vector sources. Data format: Unsigned 32-bit integral data. (OPR_SRC, FMT_NUM_U32)

In AMD's order, as its machine-readable ISA specification lists them for the ENC_VOP3 encoding (AMD CDNA 5).

GFX Target Compatibility

Per-target GFX compatibility has not yet been verified for this instruction.

Related

More in Vector Arithmetic

Reference

AMDGPU / GFX ISA

Description

Given two signed 32-bit integers and a shift count, calculate the arithmetic shift right (preserving sign bit) of the two integers, saturate the two results in the unsigned 8-bit interval [0, 255], pack the bytes and store the result into a vector register.

Example

v_ashr_pk_u8_i32 v2, v4, 0, 1

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx1250_asm_vop3-fake16.s). Not from an AMD document, and not authored here.

Sources