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 HCR.TWI, SCR.TWI, and SCTLR.nTWI.
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 |
// 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 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_WFI); if PSTATE.EL == EL0 then // Check for traps described by the OS. AArch32.CheckForWFxTrap(EL1, WFxType_WFI); if PSTATE.EL IN {EL0, EL1} && EL2Enabled() && !IsInHost() then // Check for traps described by the Hypervisor. AArch32.CheckForWFxTrap(EL2, WFxType_WFI); if HaveEL(EL3) && PSTATE.M != M32_Monitor then // Check for traps described by the Secure Monitor. AArch32.CheckForWFxTrap(EL3, WFxType_WFI); constant integer localtimeout = 1 << 64; // No local timeout event is generated WaitForInterrupt(localtimeout);
Internal version only: isa v01_31, pseudocode v2024-03_rel ; Build timestamp: 2024-03-25T10:05
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