Memory Copy, reads and writes unprivileged. These instructions perform a memory copy. The prologue, main, and epilogue instructions are expected to be run in succession and to appear consecutively in memory: CPYPT, then CPYMT, and then CPYET.
CPYPT performs some preconditioning of the arguments suitable for using the CPYMT instruction, and performs an implementation defined amount of the memory copy. CPYMT performs an implementation defined amount of the memory copy. CPYET performs the last part of the memory copy.
The inclusion of implementation defined amounts of memory copy allows some optimization of the size that can be performed.
For CPYPT, the following saturation logic is applied:
If Xn<63:55> != 000000000, the copy size Xn is saturated to 0x007FFFFFFFFFFFFF.
After that saturation logic is applied, the direction of the memory copy is based on the following algorithm:
If (Xs > Xd) && (Xd + saturated Xn) > Xs, then direction = forward
Elsif (Xs < Xd) && (Xs + saturated Xn) > Xd, then direction = backward
Else direction = implementation defined choice between forward and backward.
The architecture supports two algorithms for the memory copy: option A and option B. Which algorithm is used is implementation defined.
Portable software should not assume that the choice of algorithm is constant.
After execution of CPYPT, option A (which results in encoding PSTATE.C = 0):
After execution of CPYPT, option B (which results in encoding PSTATE.C = 1):
For CPYMT, option A (encoded by PSTATE.C = 0), the format of the arguments is:
For CPYMT, option B (encoded by PSTATE.C = 1), the format of the arguments is:
For CPYET, option A (encoded by PSTATE.C = 0), the format of the arguments is:
For CPYET, option B (encoded by PSTATE.C = 1), the format of the arguments is:
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 | 0 | 0 | 1 | 1 | 0 | 1 | Rn | Rd | ||||||||||||||
op2 |
if !HaveFeatMOPS() || sz != '00' then UNDEFINED; integer d = UInt(Rd); integer s = UInt(Rs); integer n = UInt(Rn); bits(4) options = op2; boolean rnontemporal = options<3> == '1'; boolean wnontemporal = options<2> == '1'; MOPSStage stage; case op1 of when '00' stage = MOPSStage_Prologue; when '01' stage = MOPSStage_Main; when '10' stage = MOPSStage_Epilogue; otherwise SEE "Memory Copy and Memory Set"; CheckMOPSEnabled(); if s == n || s == d || n == d || d == 31 || s == 31 || n == 31 then Constraint c = ConstrainUnpredictable(Unpredictable_MOPSOVERLAP31); assert c IN {Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_UNDEF UNDEFINED; when Constraint_NOP EndOfInstruction();
For information about the constrained unpredictable behavior of this instruction, see Architectural Constraints on UNPREDICTABLE behaviors, and particularly Memory Copy and Memory Set CPY*.
integer N = MaxBlockSizeCopiedBytes(); bits(64) toaddress = X[d, 64]; bits(64) fromaddress = X[s, 64]; bits(64) cpysize = X[n, 64]; bits(4) nzcv = PSTATE.<N,Z,C,V>; bits(8*N) readdata; integer B; boolean implements_option_a = CPYOptionA(); boolean rprivileged = if options<1> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0; boolean wprivileged = if options<0> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0; AccessDescriptor raccdesc = CreateAccDescMOPS(MemOp_LOAD, rprivileged, rnontemporal); AccessDescriptor waccdesc = CreateAccDescMOPS(MemOp_STORE, wprivileged, wnontemporal); if stage == MOPSStage_Prologue then if cpysize<63:55> != '000000000' then cpysize = 0x007FFFFFFFFFFFFF<63:0>; boolean forward = IsMemCpyForward(toaddress, fromaddress, cpysize); if implements_option_a then nzcv = '0000'; if forward then // Copy in the forward direction offsets the arguments. toaddress = toaddress + cpysize; fromaddress = fromaddress + cpysize; cpysize = Zeros(64) - cpysize; else if !forward then // Copy in the reverse direction offsets the arguments. toaddress = toaddress + cpysize; fromaddress = fromaddress + cpysize; nzcv = '1010'; else nzcv = '0010'; else CheckMemCpyParams(stage, implements_option_a, nzcv, options, d, s, n, toaddress, fromaddress, cpysize); bits(64) stagecpysize = MemCpyStageSize(stage, toaddress, fromaddress, cpysize); if implements_option_a then while SInt(stagecpysize) != 0 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(toaddress, fromaddress, cpysize); if SInt(cpysize) < 0 then assert B <= -1 * SInt(stagecpysize); readdata<B*8-1:0> = Mem[fromaddress+cpysize, B, raccdesc]; Mem[toaddress+cpysize, B, waccdesc] = readdata<B*8-1:0>; cpysize = cpysize + B; stagecpysize = stagecpysize + B; else assert B <= SInt(stagecpysize); cpysize = cpysize - B; stagecpysize = stagecpysize - B; readdata<B*8-1:0> = Mem[fromaddress+cpysize, B, raccdesc]; Mem[toaddress+cpysize, B, waccdesc] = readdata<B*8-1:0>; if stage != MOPSStage_Prologue then X[n, 64] = cpysize; else while UInt(stagecpysize) > 0 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(toaddress, fromaddress, cpysize); assert B <= UInt(stagecpysize); if nzcv<3> == '0' then // PSTATE.N readdata<B*8-1:0> = Mem[fromaddress, B, raccdesc]; Mem[toaddress, B, waccdesc] = readdata<B*8-1:0>; fromaddress = fromaddress + B; toaddress = toaddress + B; else readdata<B*8-1:0> = Mem[fromaddress-B, B, raccdesc]; Mem[toaddress-B, B, waccdesc] = readdata<B*8-1:0>; fromaddress = fromaddress - B; toaddress = toaddress - B; cpysize = cpysize - B; stagecpysize = stagecpysize - B; if stage != MOPSStage_Prologue then X[n, 64] = cpysize; X[d, 64] = toaddress; X[s, 64] = fromaddress; if stage == MOPSStage_Prologue then X[n, 64] = cpysize; X[d, 64] = toaddress; X[s, 64] = fromaddress; PSTATE.<N,Z,C,V> = nzcv;
Internal version only: isa v33.64, AdvSIMD v29.12, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T19:42
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