Atomic floating-point add, without return
This instruction atomically loads a 16-bit, 32-bit, or 64-bit value from memory, performs a floating-point add with the value held in a register, and stores the result back to memory.
This instruction:
For more information about memory ordering semantics, see Load-Acquire, Store-Release.
For information about addressing modes, see Load/Store addressing modes.
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| size | 1 | 1 | 1 | 1 | 0 | 0 | 0 | R | 1 | Rs | 1 | 0 | 0 | 0 | 0 | 0 | Rn | 1 | 1 | 1 | 1 | 1 | |||||||||
| VR | A | o3 | opc | Rt | |||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_LSFE) then EndOfDecode(Decode_UNDEF); end; let s : integer = UInt(Rs); let n : integer = UInt(Rn); let datasize : integer{} = 8 << UInt(size); let acquire : boolean = FALSE; let release : boolean = R == '1'; let tagchecked : boolean = n != 31;
| <Hs> |
Is the 16-bit name of the SIMD&FP register holding the data value to be operated on with the contents of the memory location, encoded in the "Rs" field. |
| <Xn|SP> |
Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. |
| <Ss> |
Is the 32-bit name of the SIMD&FP register holding the data value to be operated on with the contents of the memory location, encoded in the "Rs" field. |
| <Ds> |
Is the 64-bit name of the SIMD&FP register holding the data value to be operated on with the contents of the memory location, encoded in the "Rs" field. |
AArch64_CheckFPEnabled(); var address : bits(64); var value : bits(datasize); var data : bits(datasize); let accdesc : AccessDescriptor = CreateAccDescFPAtomicOp(MemAtomicOp_FPADD, acquire, release, tagchecked); value = V{datasize}(s); if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; let comparevalue : bits(datasize) = ARBITRARY : bits(datasize); // Irrelevant when not executing CAS data = MemAtomic{datasize}(address, comparevalue, value, accdesc);
2026-03_rel 2026-03-26 20:48:11
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