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Wait For Interrupt is a hint instruction that indicates that the PE can enter a low-power state and remain there until a wakeup event occurs. For more information, see Wait For Interrupt.
As described in Wait For Interrupt, the execution of a WFI instruction that would otherwise cause entry to a low-power state can be trapped to a higher Exception level, see:
It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 and T2 ) .
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
!= 1111 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | (1) | (1) | (1) | (1) | (0) | (0) | (0) | (0) | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | |||
cond |
// No additional decoding required
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 |
// No additional decoding required
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | (1) | (1) | (1) | (1) | 1 | 0 | (0) | 0 | (0) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
WFI{<c>}.W
// No additional decoding required
For more information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors.
if ConditionPassed() then
EncodingSpecificOperations();
if !InterruptPending() then
if PSTATE.EL == EL0 then
// Check for traps described by the OS which may be EL1 or EL2.
AArch32.CheckForWFxTrap(EL1, FALSE);
if PSTATE.EL IN { ifEL2Enabled() && PSTATE.EL IN {EL0, EL1} && EL2Enabled() && !} && !IsInHost() then
// Check for traps described by the Hypervisor.
AArch32.CheckForWFxTrap(EL2, FALSE);
if HaveEL(EL3) && PSTATE.M != M32_Monitor then
// Check for traps described by the Secure Monitor.
AArch32.CheckForWFxTrap(EL3, FALSE);
WaitForInterrupt();
Internal version only: isa v00_96v00_88, pseudocode r8p5_00bet2_rc5v85-xml-00bet9_rc1_1
; Build timestamp: 2019-03-28T072018-12-12T12:5933
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This document is Non-Confidential.
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