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STSMAX, STSMAXL

Atomic signed maximum on word or doubleword in memory, without return, atomically loads a 32-bit word or 64-bit doubleword from memory, compares it against the value held in a register, and stores the larger value back to memory, treating the values as signed numbers.

  • STSMAX has no memory ordering semantics.
  • STSMAXL 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 LDSMAX, LDSMAXA, LDSMAXAL, LDSMAXL. This means:

Integer
(Armv8.1)

313029282726252423222120191817161514131211109876543210
1x1110000R1Rs010000Rn11111
sizeAopcRt

32-bit LDSMAX alias (size == 10 && R == 0)

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

is equivalent to

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

and is always the preferred disassembly.

32-bit LDSMAXL alias (size == 10 && R == 1)

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

is equivalent to

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

and is always the preferred disassembly.

64-bit LDSMAX alias (size == 11 && R == 0)

STSMAX <Xs>, [<Xn|SP>]

is equivalent to

LDSMAX <Xs>, XZR, [<Xn|SP>]

and is always the preferred disassembly.

64-bit LDSMAXL alias (size == 11 && R == 1)

STSMAXL <Xs>, [<Xn|SP>]

is equivalent to

LDSMAXL <Xs>, XZR, [<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.

<Xs>

Is the 64-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 LDSMAX, LDSMAXA, LDSMAXAL, LDSMAXL 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.

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