lwat

Load Word Atomic

lwat RT,RA,FC

Loads a word from memory atomically.

Encoding

Binary Layout

18

0:5

LI

6:29

AA

30

LK

31

 

Format X-form

Opcode 0x7C00048C

Extension Base

Operands

• RT
  Target General Purpose Register
• RA
  Source General Purpose Register
• FC
  Function Code

Example

lwat r3, r4, fc

Related

More in Base

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Loads a 32-bit word from memory at an address computed from RA with atomic semantics determined by function code FC. The loaded value is placed in GPR RT. This instruction requires alignment and may be restricted to hypervisor mode depending on FC value.

Operation

EA ← RA
RT ← [EA]
# Atomic load with fence behavior determined by FC

Programming Note

EA must be a multiple of 4, and the portion of mem(EA-4,12) accessed by the instruction must be contained within an aligned 32-byte block of storage. If either of these requirements is not satisfied, the system alignment error handler is invoked.