wfe

Wait For Event

WFE

Puts the processor into a low-power state until an event occurs.

Pseudocode Operation

# Enter low-power state
while (no_event_pending) do
  wait_for_event
PC ← PC + 4

Encoding

Binary Layout

11010101000000110010

31:12

0000

11:8

010

7:5

11111

4:0

Format System Alias

Opcode 0xD503205F

Extension Base

Operands

Other forms of wfe

wfe Wait For Event (A32)
wfe Wait For Event (Thumb)

Across architectures

Spin-Wait Hint : how x86, ARM, RISC-V, and PowerISA each do this.

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xD503205F	WFE		A64		11010101000000110010 \| 0000 \| 010 \| 11111

Description

Wait For Event is a hint instruction that indicates that the PE can enter a low-power state and remain there until a wakeup event occurs. Wakeup events include the event signaled as a result of executing the SEV instruction on any PE in the multiprocessor system. For more information, see Wait For Event mechanism and Send event. As described in Wait For Event mechanism and Send event, the execution of a WFE instruction that would otherwise cause entry to a low-power state can be trapped to a higher Exception level.

Operation

integer localtimeout = 1 << 64;    // No local timeout event is generated
Hint_WFE(localtimeout, WFxType_WFE);

wfe