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 and Send Event.
As described in Wait For Event 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, see HCR.TWE, SCR.TWE, and SCTLR.nTWE.
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 | 0 | |||
| 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 | 0 | 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 | 0 |
// 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 IsEventRegisterSet() then ClearEventRegister(); else if HaveEL(EL3) && EL3SDDUndefPriority() then // Check for traps described by the Secure Monitor. // If the trap is enabled, the instruction will be UNDEFINED because EDSCR.SDD is 1. AArch32.CheckForWFxTrap(EL3, WFxType_WFE); if PSTATE.EL == EL0 then // Check for traps described by the OS. AArch32.CheckForWFxTrap(EL1, WFxType_WFE); if PSTATE.EL IN {EL0, EL1} && EL2Enabled() && !IsInHost() then // Check for traps described by the Hypervisor. AArch32.CheckForWFxTrap(EL2, WFxType_WFE); if HaveEL(EL3) && PSTATE.M != M32_Monitor then // Check for traps described by the Secure Monitor. AArch32.CheckForWFxTrap(EL3, WFxType_WFE); constant integer localtimeout = 1 << 64; // No local timeout event is generated WaitForEvent(localtimeout);
Internal version only: isa v01_31, pseudocode v2024-03_rel ; Build timestamp: 2024-03-25T10:05
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