v_ashrrev_i64 GPU Native ISA AMD Vector

Vector Arithmetic

v_ashrrev_i64

Given a shift count in the first vector input, calculate the arithmetic shift right (preserving sign bit) of the second vector input and store the…

Encoding

Binary Layout (AMD CDNA 5)
NEG
63:61
OMOD
60:59
SRC2
58:50
SRC1
49:41
SRC0
40:32
110101
31:26
1100111110
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 830 in OP rebuilds 0x00000000D73E0000, an identifier AMD lists for this encoding. Not the same in every generation: AMD CDNA 4 (opcode 657, field layout), AMD CDNA 3 (opcode 657, field layout), AMD CDNA 2 (opcode 657, field layout), AMD CDNA 1 (opcode 657, field layout), AMD RDNA 3.5 (field layout), AMD RDNA 3 (field layout), AMD RDNA 2 (opcode 769, field layout), AMD RDNA 1 (opcode 769, field layout). The same in AMD RDNA 4.

Format VOP3
Width 64 bits
Opcode 830
Identifier 0x00000000D73E0000

Operands

  • VDST
    Written. Operand must be a vector GPR. Uses an 8-bit operand field. Data format: Signed 64-bit integral data. (OPR_VGPR, FMT_NUM_I64)
  • SRC0
    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)
  • SRC1
    Read. All operands. Covers all operands that are allowed as scalar or vector sources. Data format: Signed 64-bit integral data. (OPR_SRC, FMT_NUM_I64)

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

GFX Target Compatibility

TargetSupport
gfx1100✅ Supported

Related

More in Vector Arithmetic

Reference

AMDGPU / GFX ISA

Description

Given a shift count in the first vector input, calculate the arithmetic shift right (preserving sign bit) of the second vector input and store the result into a vector register.

Semantics

D0.i64 = (S1.i64 >> S0[5 : 0].u32)

Example

v_ashrrev_i64 v[5:6], -1, -1

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

Sources