s_buffer_load_i8 GPU Native ISA AMD Scalar

Scalar Memory

s_buffer_load_i8

Load 8 bits of signed data from a scalar buffer surface, sign extend to 32 bits and store the result into a scalar register.

Encoding

Binary Layout (AMD CDNA 5)
SOFFSET
63:57
SCALE_OFFSET
56
IOFFSET
55:32
111101
31:26
unassigned
25
TH
24:23
SCOPE
22:21
NV
20
unassigned
19
011000
18:13
SDATA
12:6
SBASE
5:0
 

The ENC_SMEM layout from AMD's machine-readable ISA specification (AMD CDNA 5). Opcode 24 in OP rebuilds 0x00000000F4030000, an identifier AMD lists for this encoding. Bits marked unassigned have no field in the specification. Not the same in every generation: AMD RDNA 4 (field layout).

Format SMEM
Width 64 bits
Opcode 24
Identifier 0x00000000F4030000

Operands

  • SDATA
    Written. Any scalar GPR operand including VCC and NULL. Data format: Signed 32-bit integral data. (OPR_SREG, FMT_NUM_I32)
  • SBASE
    Read. Any scalar GPR operand including VCC and NULL. Data format: 128-bit buffer resource constant. (OPR_SREG, FMT_RSRC_SCALAR)
  • SOFFSET
    Read. Operand is a scalar memory offset, which may come from a scalar GPR, from M0 or from a 24-bit immediate constant. Data format: 32 bits of arbitrary data. (OPR_SMEM_OFFSET, FMT_NUM_B32)

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

GFX Target Compatibility

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

Related

More in Scalar Memory

Reference

AMDGPU / GFX ISA

Example

s_buffer_load_i8 s5, s[4:7], s0

A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx12_asm_smem.s). Not from an AMD document, and not authored here.

Sources