buffer_atomic_umax_x2 GPU Native ISA AMD Vector

Buffer Memory

buffer_atomic_umax_x2

Select the maximum of two unsigned 64-bit integer inputs, given two values stored in the data register and a location in a buffer surface.

Also written as buffer_atomic_max_u64. AMD's machine-readable ISA specification lists this name for the same instruction.

Encoding

Binary Layout (AMD CDNA 4)
SOFFSET
63:56
ACC
55
unassigned
54:53
SRSRC
52:48
VDATA
47:40
VADDR
39:32
111000
31:26
unassigned
25
1100111
24:18
NT
17
LDS
16
SC1
15
SC0
14
IDXEN
13
OFFEN
12
OFFSET
11:0
 

The ENC_MUBUF layout from AMD's machine-readable ISA specification (AMD CDNA 4). Opcode 103 in OP rebuilds 0x00000000E19C0000, an identifier AMD lists for this encoding. Bits marked unassigned have no field in the specification. Not the same in every generation: AMD CDNA 2 (field layout), AMD CDNA 1 (field layout), AMD RDNA 2 (layout not verifiable), AMD RDNA 1 (layout not verifiable). The same in AMD CDNA 3.

Format MUBUF
Width 64 bits
Opcode 103
Identifier 0x00000000E19C0000

Operands

  • VDATA
    Written. N/A Data format: Value can be anything. (OPR_VGPR_OR_ACCVGPR, FMT_ANY)
  • VADDR
    Read. N/A Data format: Value can be anything. (OPR_VGPR, FMT_ANY)
  • SRSRC
    Read. N/A Data format: 128-bit buffer resource constant. (OPR_SREG, FMT_RSRC_SCRATCH)
  • SOFFSET
    Read. N/A Data format: Value can be anything. (OPR_SSRC_NOLIT, FMT_ANY)

In AMD's order, as its machine-readable ISA specification lists them for the ENC_MUBUF encoding (AMD CDNA 4).

GFX Target Compatibility

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

Related

More in Buffer Memory

Reference

AMDGPU / GFX ISA

Description

Select the maximum of two unsigned 64-bit integer inputs, given two values stored in the data register and a location in a buffer surface. Update the buffer surface with the selected value. Store the original value from buffer surface into a vector register iff the SC0 bit is set.

Example

buffer_atomic_umax_x2 v[5:6], off, s[8:11], s3

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx10_asm_mubuf.s). Not from an AMD document, and not authored here.

Sources