STUMAXB, STUMAXLB

Atomic unsigned maximum on byte in memory, without return, atomically loads an 8-bit byte from memory, compares it against the value held in a register, and stores the larger value back to memory, treating the values as unsigned numbers.

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

This is an alias of LDUMAXB, LDUMAXAB, LDUMAXALB, LDUMAXLB. This means:

Integer
(FEAT_LSE)

313029282726252423222120191817161514131211109876543210
001110000R1Rs011000Rn11111
sizeVRAo3opcRt

No memory ordering (R == 0)

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

is equivalent to

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

and is always the preferred disassembly.

Release (R == 1)

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

is equivalent to

LDUMAXLB <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 LDUMAXB, LDUMAXAB, LDUMAXALB, LDUMAXLB 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.


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

Copyright © 2010-2024 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.