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STUMAX, STUMAXL, STUMAXL

Atomic unsigned maximum on word or doubleword in memory, without return.

Syntax

STUMAX Ws, [Xn|SP] ; 32-bit, no memory ordering general registers

STUMAXL Ws, [Xn|SP] ; 32-bit, release general registers

STUMAX Xs, [Xn|SP] ; 64-bit, no memory ordering general registers

STUMAXL Xs, [Xn|SP] ; 64-bit, release general registers

Where:

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.
Xn|SP
Is the 64-bit name of the general-purpose base register or stack pointer.
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.

Architectures supported

Supported in ARMv8.1 and later.

Usage

Atomic unsigned 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 unsigned numbers.

  • STUMAX has no memory ordering semantics.
  • STUMAXL stores to memory with release semantics, as described in Load-Acquire, Store-Release in the ARMv8-A Architecture Reference Manual.

For information about memory accesses see Load/Store addressing modes in the ARMv8-A Architecture Reference Manual.