Arm Compiler armasm User Guide : 17.66 LDUMINAB, LDUMINALB, LDUMINB, LDUMINLB

17.66 LDUMINAB, LDUMINALB, LDUMINB, LDUMINLB

Atomic unsigned minimum on byte in memory.

Syntax

LDUMINAB Ws, Wt, [Xn|SP] ; Acquire general registers

LDUMINALB Ws, Wt, [Xn|SP] ; Acquire and release general registers

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

LDUMINLB Ws, Wt, [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.
Wt: Is the 32-bit name of the general-purpose register to be loaded.
Xn|SP: Is the 64-bit name of the general-purpose base register or stack pointer.

Architectures supported

Supported in the Arm^®v8.1 architecture and later.

Usage

Atomic unsigned minimum on byte in memory atomically loads an 8-bit byte from memory, compares it against the value held in a register, and stores the smaller value back to memory, treating the values as unsigned numbers. The value initially loaded from memory is returned in the destination register.

If the destination register is not WZR, LDUMINAB and LDUMINALB load from memory with acquire semantics.
LDUMINLB and LDUMINALB store to memory with release semantics.
LDUMINB has no memory ordering requirements.

For more information about memory ordering semantics see Load-Acquire, Store-Release in the Arm^® Architecture Reference Manual Arm^®v8, for Arm^®v8‑A architecture profile.

For information about memory accesses see Load/Store addressing modes in the Arm^® Architecture Reference Manual Arm^®v8, for Arm^®v8‑A architecture profile.

Related references

17.1 A64 data transfer instructions in alphabetical order

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