CPYPN, CPYMN, CPYEN -- A64

These instructions copy a requested number of bytes in memory from a source address to a destination address. The prologue, main, and epilogue instructions are expected to be run in succession and to appear consecutively in memory: CPYPN, then CPYMN, and then CPYEN.

CPYPN performs some preconditioning of the arguments suitable for using the CPYMN instruction, and copies an IMPLEMENTATION DEFINED portion of the requested number of bytes. CPYMN copies a further IMPLEMENTATION DEFINED portion of the remaining bytes. CPYEN copies any final remaining bytes.

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

Integer
(FEAT_MOPS)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_MOPS) || sz != '00' then EndOfDecode(Decode_UNDEF); end; var memcpy : CPYParams; memcpy.d = UInt(Rd); memcpy.s = UInt(Rs); memcpy.n = UInt(Rn); let options : bits(4) = op2; let rnontemporal : boolean = options[3] == '1'; let wnontemporal : boolean = options[2] == '1'; case op1 of when '00' => memcpy.stage = MOPSStage_Prologue; when '01' => memcpy.stage = MOPSStage_Main; when '10' => memcpy.stage = MOPSStage_Epilogue; end;

Assembler Symbols

Operation

CheckMOPSEnabled(); CheckCPYConstrainedUnpredictable(memcpy.n, memcpy.d, memcpy.s); memcpy.nzcv = PSTATE.[N,Z,C,V]; memcpy.toaddress = X{64}(memcpy.d); memcpy.fromaddress = X{64}(memcpy.s); if memcpy.stage == MOPSStage_Prologue then memcpy.cpysize = UInt(X{64}(memcpy.n)); else memcpy.cpysize = SInt(X{64}(memcpy.n)); end; memcpy.implements_option_a = CPYOptionA(); let rprivileged : boolean = (if options[1] == '1' then AArch64_IsUnprivAccessPriv() else PSTATE.EL != EL0); let wprivileged : boolean = (if options[0] == '1' then AArch64_IsUnprivAccessPriv() else PSTATE.EL != EL0); let raccdesc : AccessDescriptor = CreateAccDescMOPS(MemOp_LOAD, rprivileged, rnontemporal); let waccdesc : AccessDescriptor = CreateAccDescMOPS(MemOp_STORE, wprivileged, wnontemporal); if memcpy.stage == MOPSStage_Prologue then if memcpy.cpysize > ArchMaxMOPSCPYSize then memcpy.cpysize = ArchMaxMOPSCPYSize; end; memcpy.forward = IsMemCpyForward(memcpy); if memcpy.implements_option_a then memcpy.nzcv = '0000'; if memcpy.forward then // Copy in the forward direction offsets the arguments. memcpy.toaddress = memcpy.toaddress + memcpy.cpysize; memcpy.fromaddress = memcpy.fromaddress + memcpy.cpysize; memcpy.cpysize = 0 - memcpy.cpysize; end; else if !memcpy.forward then // Copy in the reverse direction offsets the arguments. memcpy.toaddress = memcpy.toaddress + memcpy.cpysize; memcpy.fromaddress = memcpy.fromaddress + memcpy.cpysize; memcpy.nzcv = '1010'; else memcpy.nzcv = '0010'; end; end; end; memcpy.stagecpysize = MemCpyStageSize(memcpy); if memcpy.stage != MOPSStage_Prologue then memcpy.forward = memcpy.cpysize < 0 || (!memcpy.implements_option_a && memcpy.nzcv[3] == '0'); CheckMemCpyParams(memcpy, options); end; var copied : integer; var iswrite : boolean; var memaddrdesc : AddressDescriptor; var memstatus : PhysMemRetStatus; var fault : boolean = FALSE; var B : MOPSBlockSize = 0; if memcpy.implements_option_a then while memcpy.stagecpysize != 0 && !fault looplimit ArchMaxMOPSCPYSize do // IMP DEF selection of the block size that is worked on. While many // implementations might make this constant, that is not assumed. B = CPYSizeChoice(memcpy); if memcpy.forward then assert B <= -1 * memcpy.stagecpysize; (copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes( memcpy.toaddress + memcpy.cpysize, memcpy.fromaddress + memcpy.cpysize, memcpy.forward, B, raccdesc, waccdesc); if copied != B then fault = TRUE; else memcpy.cpysize = memcpy.cpysize + B; memcpy.stagecpysize = memcpy.stagecpysize + B; end; else assert B <= memcpy.stagecpysize; memcpy.cpysize = memcpy.cpysize - B; memcpy.stagecpysize = memcpy.stagecpysize - B; (copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes( memcpy.toaddress + memcpy.cpysize, memcpy.fromaddress + memcpy.cpysize, memcpy.forward, B, raccdesc, waccdesc); if copied != B then fault = TRUE; memcpy.cpysize = memcpy.cpysize + B; memcpy.stagecpysize = memcpy.stagecpysize + B; end; end; end; else while memcpy.stagecpysize > 0 && !fault looplimit ArchMaxMOPSCPYSize do // IMP DEF selection of the block size that is worked on. While many // implementations might make this constant, that is not assumed. B = CPYSizeChoice(memcpy); assert B <= memcpy.stagecpysize; if memcpy.forward then (copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes(memcpy.toaddress, memcpy.fromaddress, memcpy.forward, B, raccdesc, waccdesc); if copied != B then fault = TRUE; else memcpy.fromaddress = memcpy.fromaddress + B; memcpy.toaddress = memcpy.toaddress + B; end; else (copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes(memcpy.toaddress - B, memcpy.fromaddress - B, memcpy.forward, B, raccdesc, waccdesc); if copied != B then fault = TRUE; else memcpy.fromaddress = memcpy.fromaddress - B; memcpy.toaddress = memcpy.toaddress - B; end; end; if !fault then memcpy.cpysize = memcpy.cpysize - B; memcpy.stagecpysize = memcpy.stagecpysize - B; end; end; end; UpdateCpyRegisters(memcpy, fault, copied); if fault then if IsFault(memaddrdesc) then AArch64_Abort(memaddrdesc.fault); else let accdesc : AccessDescriptor = if iswrite then waccdesc else raccdesc; HandleExternalAbort(memstatus, iswrite, memaddrdesc, B, accdesc); end; end; if memcpy.stage == MOPSStage_Prologue then PSTATE.[N,Z,C,V] = memcpy.nzcv; end;

2026-03_rel 2026-03-26 20:48:11

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
sz		0	1	1	1	0	1	op1		0	Rs					1	1	0	0	0	1	Rn					Rd
					o0											op2

<Xn>	For the "Prologue" variant: is the 64-bit name of the general-purpose register that holds the number of bytes to be transferred and is updated by the instruction to encode the remaining size and destination, 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 transferred, encoded in the "Rn" field.
	For the "Epilogue" variant: is the 64-bit name of the general-purpose register that holds an encoding of the number of bytes to be transferred and is set to zero on completion of the instruction, encoded in the "Rn" field.