flat_atomic_cmpswap_x2 GPU Native ISA AMD Vector
FLAT ATOMIC CMPSWAP X2 Flat Memory
flat_atomic_cmpswap_x2
Compare two unsigned 64-bit integer values stored in the data comparison register and a location in the flat aperture.
Encoding
Verified bit-level encoding data is not yet available for this instruction.
The instruction-format classification below (FLAT)
is well-documented and stable; exact per-target opcode/field bit positions have not
yet been imported from a verified source.
Operands
Operand details have not yet been curated for this instruction.
GFX Target Compatibility
| Target | Support |
|---|---|
| gfx1100 | ✅ Supported |
Related
More in Flat Memory
Reference
AMDGPU / GFX ISA
Description
Compare two unsigned 64-bit integer values stored in the data comparison register and a location in the flat aperture. Modify the memory location with a value in the data source register iff the comparison is equal. Store the original value from flat aperture into a vector register iff the SC0 bit is set. NOTE: RETURN_DATA[2:3] is not modified.
Semantics
addr = CalcFlatAddr(ADDR.b32, OFFSET.b32);
tmp = MEM[addr].u64;
src = DATA[63 : 0].u64;
cmp = DATA[127 : 64].u64;
MEM[addr].u64 = tmp == cmp ? src : tmp;
RETURN_DATA.u64 = tmp
Example
flat_atomic_cmpswap_x2 v[1:2], v[2:5]A real instruction accepted by the LLVM assembler, taken verbatim from LLVM's own AMDGPU MC test suite (gfx11). Not from an AMD document, and not authored here.
Sources
- User Guide for AMDGPU Backend ↗ - LLVM Project
-
"AMD Instinct MI300" Instruction Set Architecture: Reference Guide ↗
- Advanced Micro Devices, Inc.
Reference Guide, page 493. - LLVM MC assembler tests for AMDGPU (gfx11) ↗ - LLVM Project