SETPN, SETMN, SETEN

Memory Set, non-temporal. These instructions perform a memory set using the value in the bottom byte of the source register. The prologue, main, and epilogue instructions are expected to be run in succession and to appear consecutively in memory: SETPN, then SETMN, and then SETEN.

SETPN performs some preconditioning of the arguments suitable for using the SETMN instruction, and performs an IMPLEMENTATION DEFINED amount of the memory set. SETMN performs an IMPLEMENTATION DEFINED amount of the memory set. SETEN performs the last part of the memory set.


Note

The inclusion of IMPLEMENTATION DEFINED amounts of memory set allows some optimization of the size that can be performed.


The architecture supports two algorithms for the memory set: option A and option B. Which algorithm is used is IMPLEMENTATION DEFINED.


Note

Portable software should not assume that the choice of algorithm is constant.


After execution of SETPN, option A (which results in encoding PSTATE.C = 0):

After execution of SETPN, option B (which results in encoding PSTATE.C = 1):

For SETMN, option A (encoded by PSTATE.C = 0), the format of the arguments is:

For SETMN, option B (encoded by PSTATE.C = 1), the format of the arguments is:

For SETEN, option A (encoded by PSTATE.C = 0), the format of the arguments is:

For SETEN, option B (encoded by PSTATE.C = 1), the format of the arguments is:

Integer
(FEAT_MOPS)

313029282726252423222120191817161514131211109876543210
sz011001110Rsxx1001RnRd
o0op1op2

Prologue (op2 == 0010)

SETPN [<Xd>]!, <Xn>!, <Xs>

Main (op2 == 0110)

SETMN [<Xd>]!, <Xn>!, <Xs>

Epilogue (op2 == 1010)

SETEN [<Xd>]!, <Xn>!, <Xs>

if !IsFeatureImplemented(FEAT_MOPS) || sz != '00' then UNDEFINED; SETParams memset; memset.d = UInt(Rd); memset.s = UInt(Rs); memset.n = UInt(Rn); bits(2) options = op2<1:0>; boolean nontemporal = options<1> == '1'; case op2<3:2> of when '00' memset.stage = MOPSStage_Prologue; when '01' memset.stage = MOPSStage_Main; when '10' memset.stage = MOPSStage_Epilogue; otherwise UNDEFINED;

For information about the CONSTRAINED UNPREDICTABLE behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly Memory Copy and Memory Set SET*.

Assembler Symbols

<Xd>

For the prologue variant: is the 64-bit name of the general-purpose register that holds the destination address and is updated by the instruction, encoded in the "Rd" field.

For the epilogue and main variant: is the 64-bit name of the general-purpose register that holds an encoding of the destination address and for option B is updated by the instruction, encoded in the "Rd" field.

<Xn>

For the prologue variant: is the 64-bit name of the general-purpose register that holds the number of bytes to be set and is updated by the instruction, encoded in the "Rn" field.

For the main variant: is the 64-bit name of the general-purpose register that holds an encoding of the number of bytes to be set and is updated by the instruction, encoded in the "Rn" field.

For the epilogue variant: is the 64-bit name of the general-purpose register that holds the number of bytes to be set and is set to zero at the end of the instruction, encoded in the "Rn" field.

<Xs>

Is the 64-bit name of the general-purpose register that holds the source data, encoded in the "Rs" field.

Operation

CheckMOPSEnabled(); CheckSETConstrainedUnpredictable(memset.n, memset.d, memset.s); bits(8) data = X[memset.s, 8]; integer B; memset.is_setg = FALSE; memset.nzcv = PSTATE.<N,Z,C,V>; memset.toaddress = X[memset.d, 64]; if memset.stage == MOPSStage_Prologue then memset.setsize = UInt(X[memset.n, 64]); else memset.setsize = SInt(X[memset.n, 64]); memset.implements_option_a = SETOptionA(); boolean privileged = if options<0> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0; AccessDescriptor accdesc = CreateAccDescMOPS(MemOp_STORE, privileged, nontemporal); if memset.stage == MOPSStage_Prologue then if memset.setsize > 0x7FFFFFFFFFFFFFFF then memset.setsize = 0x7FFFFFFFFFFFFFFF; if memset.implements_option_a then memset.nzcv = '0000'; memset.toaddress = memset.toaddress + memset.setsize; memset.setsize = 0 - memset.setsize; else memset.nzcv = '0010'; memset.stagesetsize = MemSetStageSize(memset); if memset.stage != MOPSStage_Prologue then CheckMemSetParams(memset, options); AddressDescriptor memaddrdesc; PhysMemRetStatus memstatus; integer memory_set; boolean fault = FALSE; if memset.implements_option_a then while memset.stagesetsize < 0 && !fault do // IMP DEF selection of the block size that is worked on. While many // implementations might make this constant, that is not assumed. B = SETSizeChoice(memset, 1); assert B <= -1 * memset.stagesetsize; (memory_set, memaddrdesc, memstatus) = MemSetBytes(memset.toaddress + memset.setsize, data, B, accdesc); if memory_set != B then fault = TRUE; else memset.setsize = memset.setsize + B; memset.stagesetsize = memset.stagesetsize + B; else while memset.stagesetsize > 0 && !fault do // IMP DEF selection of the block size that is worked on. While many // implementations might make this constant, that is not assumed. B = SETSizeChoice(memset, 1); assert B <= memset.stagesetsize; (memory_set, memaddrdesc, memstatus) = MemSetBytes(memset.toaddress, data, B, accdesc); if memory_set != B then fault = TRUE; else memset.toaddress = memset.toaddress + B; memset.setsize = memset.setsize - B; memset.stagesetsize = memset.stagesetsize - B; UpdateSetRegisters(memset, fault, memory_set); if fault then if IsFault(memaddrdesc) then AArch64.Abort(memaddrdesc.vaddress, memaddrdesc.fault); else boolean iswrite = TRUE; HandleExternalAbort(memstatus, iswrite, memaddrdesc, B, accdesc); if memset.stage == MOPSStage_Prologue then PSTATE.<N,Z,C,V> = memset.nzcv;


Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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