Hint instruction is for the instruction set space that is reserved for architectural hint instructions.
Some encodings described here are unallocated in this revision of the architecture, and behave as NOPs. These encodings might be allocated to other hint functionality in future revisions of the architecture.
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 |
1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | CRm | op2 | 1 | 1 | 1 | 1 | 1 |
SystemHintOp op; case CRm:op2 of when '0000 000' op = SystemHintOp_NOP; when '0000 001' op = SystemHintOp_YIELD; when '0000 010' op = SystemHintOp_WFE; when '0000 011' op = SystemHintOp_WFI; when '0000 100' op = SystemHintOp_SEV; when '0000 101' op = SystemHintOp_SEVL; when '0010 000' op = if HaveRASExt() then SystemHintOp_ESB else SystemHintOp_NOP; when '0010 001' op = if HaveStatisticalProfiling() then SystemHintOp_PSB else SystemHintOp_NOP; otherwise op = SystemHintOp_NOP;
case op of when SystemHintOp_YIELD Hint_Yield(); when SystemHintOp_WFE if IsEventRegisterSet() then ClearEventRegister(); else if PSTATE.EL == EL0 then // Check for traps described by the OS which may be EL1 or EL2. AArch64.CheckForWFxTrap(EL1, TRUE); if HaveEL(EL2) && !IsSecure() && PSTATE.EL IN {EL0,EL1} && !IsInHost() then // Check for traps described by the Hypervisor. AArch64.CheckForWFxTrap(EL2, TRUE); if HaveEL(EL3) && PSTATE.EL != EL3 then // Check for traps described by the Secure Monitor. AArch64.CheckForWFxTrap(EL3, TRUE); WaitForEvent(); when SystemHintOp_WFI if !InterruptPending() then if PSTATE.EL == EL0 then // Check for traps described by the OS which may be EL1 or EL2. AArch64.CheckForWFxTrap(EL1, FALSE); if HaveEL(EL2) && !IsSecure() && PSTATE.EL IN {EL0,EL1} && !IsInHost() then // Check for traps described by the Hypervisor. AArch64.CheckForWFxTrap(EL2, FALSE); if HaveEL(EL3) && PSTATE.EL != EL3 then // Check for traps described by the Secure Monitor. AArch64.CheckForWFxTrap(EL3, FALSE); WaitForInterrupt(); when SystemHintOp_SEV SendEvent(); when SystemHintOp_SEVL SendEventLocal(); when SystemHintOp_ESB ErrorSynchronizationBarrier(MBReqDomain_FullSystem, MBReqTypes_All); AArch64.ESBOperation(); if HaveEL(EL2) && !IsSecure() && PSTATE.EL IN {EL0,EL1} then AArch64.vESBOperation(); TakeUnmaskedSErrorInterrupts(); when SystemHintOp_PSB ProfilingSynchronizationBarrier(); otherwise // do nothing
Internal version only: isa v25.07, AdvSIMD v23.0, pseudocode v31.3
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