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DGH

DGH is a hint instruction. A DGH instruction is not expected to be performance optimal to merge memory accesses with Normal Non-cacheable or Device-GRE attributes appearing in program order before the hint instruction with any memory accesses appearing after the hint instruction into a single memory transaction on an interconnect.

System
(FEAT_DGH)

313029282726252423222120191817161514131211109876543210
11010101000000110010000011011111
CRmop2

DGH

SystemHintOpif !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 '0000 110' if !HaveDGHExt() then EndOfInstruction(); // Instruction executes as NOP op = SystemHintOp_DGH; when '0000 111' SEE "XPACLRI"; when '0001 xxx' case op2 of when '000' SEE "PACIA1716"; when '010' SEE "PACIB1716"; when '100' SEE "AUTIA1716"; when '110' SEE "AUTIB1716"; otherwise EndOfInstruction(); // Instruction executes as NOP when '0010 000' if !HaveRASExt() then EndOfInstruction(); // Instruction executes as NOP op = SystemHintOp_ESB; when '0010 001' if !HaveStatisticalProfiling() then EndOfInstruction(); // Instruction executes as NOP op = SystemHintOp_PSB; when '0010 010' if !HaveSelfHostedTrace() then EndOfInstruction(); // Instruction executes as NOP op = SystemHintOp_TSB; when '0010 100' op = SystemHintOp_CSDB; when '0011 xxx' case op2 of when '000' SEE "PACIAZ"; when '001' SEE "PACIASP"; when '010' SEE "PACIBZ"; when '011' SEE "PACIBSP"; when '100' SEE "AUTIAZ"; when '101' SEE "AUTHASP"; when '110' SEE "AUTIBZ"; when '111' SEE "AUTIBSP"; when '0100 xx0' op = SystemHintOp_BTI; // Check branch target compatibility between BTI instruction and PSTATE.BTYPE SetBTypeCompatible(BTypeCompatible_BTI() then(op2<2:1>)); otherwise EndOfInstruction();(); // Instruction executes as NOP

Operation

case op of when SystemHintOp_YIELDHint_Yield(); when SystemHintOp_DGHHint_DGH(); when SystemHintOp_WFE integer localtimeout = -1; // No local timeout event is generated Hint_WFE(localtimeout, WFxType_WFE); when SystemHintOp_WFI integer localtimeout = -1; // No local timeout event is generated Hint_WFI(localtimeout, WFxType_WFI); when SystemHintOp_SEVSendEvent(); when SystemHintOp_SEVLSendEventLocal(); when SystemHintOp_ESBSynchronizeErrors(); AArch64.ESBOperation(); if PSTATE.EL IN {EL0, EL1} && EL2Enabled() then AArch64.vESBOperation(); TakeUnmaskedSErrorInterrupts(); when SystemHintOp_PSBProfilingSynchronizationBarrier(); when SystemHintOp_TSBTraceSynchronizationBarrier(); when SystemHintOp_CSDBConsumptionOfSpeculativeDataBarrier(); when SystemHintOp_BTISetBTypeNext();('00'); otherwise // do nothing


Internal version only: isa v32.13, AdvSIMD v29.05, pseudocode v2020-12, sve v2020-12 ; Build timestamp: 2020-12-16T162020-12-16T14:1917

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