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## STADDB, STADDLB

Atomic add on byte in memory, without return, atomically loads an 8-bit byte from memory, adds the value held in a register to it, and stores the result back to memory.

- STADDB does not have release semantics.
- STADDLB stores to memory with release semantics, as described in Load-Acquire, Store-Release.

For information about memory accesses, see Load/Store addressing modes.

This is an alias of LDADDB, LDADDAB, LDADDALB, LDADDLB. This means:

- The encodings in this description are named to match the encodings of LDADDB, LDADDAB, LDADDALB, LDADDLB.
- The description of LDADDB, LDADDAB, LDADDALB, LDADDLB gives the operational pseudocode, any constrained unpredictable behavior, and any operational information for this instruction.

### Integer
(FEAT_LSE)

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
0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | R | 1 | Rs | 0 | 0 | 0 | 0 | 0 | 0 | Rn | 1 | 1 | 1 | 1 | 1
size |  |  |  | A |  |  |  |  | opc |  |  | Rt

#### No memory ordering (R == 0)

STADDB <Ws>, [<Xn|SP>]

is equivalent to

LDADDB <Ws>, WZR, [<Xn|SP>]

and is always the preferred disassembly.

#### Release (R == 1)

STADDLB <Ws>, [<Xn|SP>]

is equivalent to

LDADDLB <Ws>, WZR, [<Xn|SP>]

and is always the preferred disassembly.

### Assembler Symbols

<Ws> | Is the 32-bit name of the general-purpose 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.

### Operation

The description of LDADDB, LDADDAB, LDADDALB, LDADDLB gives the operational pseudocode for this instruction.

### Operational information

If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: isa v33.64, AdvSIMD v29.12, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T19:42

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