STUMAXH, STUMAXLH

Atomic unsigned maximum on halfword in memory, without return

This instruction atomically loads a 16-bit halfword 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.

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

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

This is an alias of LDUMAXH, LDUMAXAH, LDUMAXALH, LDUMAXLH. This means:

The encodings in this description are named to match the encodings of LDUMAXH, LDUMAXAH, LDUMAXALH, LDUMAXLH.
The description of LDUMAXH, LDUMAXAH, LDUMAXALH, LDUMAXLH 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	1	1	1	1	0	0	0	0	R	1	Rs					0	1	1	0	0	0	Rn					1	1	1	1	1
size					VR			A								o3	opc										Rt

Encoding for the No memory ordering variant

Applies when (R == 0)

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

is equivalent to

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

and is always the preferred disassembly.

Encoding for the Release variant

Applies when (R == 1)

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

is equivalent to

LDUMAXLH <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