17.122 STUMAXB, STUMAXLB

Atomic unsigned maximum on byte in memory, without return.

Syntax

STUMAXB Ws, [Xn|SP] ; No memory ordering general registers

STUMAXLB Ws, [Xn|SP] ; 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.

Architectures supported

Supported in ARMv8.1 and later.

Usage

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.

  • STUMAXB has no memory ordering semantics.
  • STUMAXLB stores to memory with release semantics, as described in Load-Acquire, Store-Release.

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

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