s_memtime GPU Native ISA AMD Scalar

Scalar Memory

s_memtime

Return current 64-bit timestamp.

Encoding

Binary Layout (AMD CDNA 4)
SOFFSET
63:57
unassigned
56:53
OFFSET
52:32
110000
31:26
00100100
25:18
IMM
17
GLC
16
NV
15
SOFFSET_EN
14
unassigned
13
SDATA
12:6
SBASE
5:0
 

The ENC_SMEM layout from AMD's machine-readable ISA specification (AMD CDNA 4). Opcode 36 in OP rebuilds 0x00000000C0900000, an identifier AMD lists for this encoding. Bits marked unassigned have no field in the specification. Not the same in every generation: AMD RDNA 2 (field layout), AMD RDNA 1 (field layout). The same in AMD CDNA 3, AMD CDNA 2, AMD CDNA 1.

Format SMEM
Width 64 bits
Opcode 36
Identifier 0x00000000C0900000

Operands

  • SDATA
    Written. N/A Data format: N/A (OPR_SREG, FMT_NUM_B64)

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

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_memtime vcc

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