CPYPWTN, CPYMWTN, CPYEWTN

Memory copy, writes unprivileged, reads and writes non-temporal

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: CPYPWTN, then CPYMWTN, and then CPYEWTN.

CPYPWTN performs some preconditioning of the arguments suitable for using the CPYMWTN instruction, and performs an IMPLEMENTATION DEFINED amount of the memory copy. CPYMWTN performs an IMPLEMENTATION DEFINED amount of the memory copy. CPYEWTN performs the last part of the memory copy.

For CPYPWTN, 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.

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

• PSTATE.{N,Z,V} are set to {0,0,0}.
• If the copy is in the forward direction, then:
  • Xs holds the original Xs + saturated Xn.
  • Xd holds the original Xd + saturated Xn.
  • Xn holds -1* saturated Xn + an IMPLEMENTATION DEFINED number of bytes copied.
• If the copy is in the backward direction, then:
  • Xs and Xd are unchanged.
  • Xn holds the saturated value of Xn - an IMPLEMENTATION DEFINED number of bytes copied.

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

• If the copy is in the forward direction, then:
  • Xs holds the original Xs + an IMPLEMENTATION DEFINED number of bytes copied.
  • Xd holds the original Xd + an IMPLEMENTATION DEFINED number of bytes copied.
  • Xn holds the saturated Xn - an IMPLEMENTATION DEFINED number of bytes copied.
  • PSTATE.{N,Z,V} are set to {0,0,0}.
• If the copy is in the backward direction, then:
  • Xs holds the original Xs + saturated Xn - an IMPLEMENTATION DEFINED number of bytes copied.
  • Xd holds the original Xd + saturated Xn - an IMPLEMENTATION DEFINED number of bytes copied.
  • Xn holds the saturated Xn - an IMPLEMENTATION DEFINED number of bytes copied.
  • PSTATE.{N,Z,V} are set to {1,0,0}.

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

• Xn is treated as a signed 64-bit number.
• If the copy is in the forward direction (Xn is a negative number), then:
  • Xn holds -1* the number of bytes remaining to be copied in the memory copy in total.
  • Xs holds the lowest address that the copy is copied from -Xn.
  • Xd holds the lowest address that the copy is made to -Xn.
  • At the end of the instruction, the value of Xn is written back with -1* the number of bytes remaining to be copied in the memory copy in total.
• If the copy is in the backward direction (Xn is a positive number), then:
  • Xn holds the number of bytes remaining to be copied in the memory copy in total.
  • Xs holds the highest address that the copy is copied from -Xn+1.
  • Xd holds the highest address that the copy is copied to -Xn+1.
  • At the end of the instruction, the value of Xn is written back with the number of bytes remaining to be copied in the memory copy in total.

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

• Xn holds the number of bytes to be copied in the memory copy in total.
• If the copy is in the forward direction (PSTATE.N == 0), then:
  • Xs holds the lowest address that the copy is copied from.
  • Xd holds the lowest address that the copy is copied to.
  • At the end of the instruction:
    • the value of Xn is written back with the number of bytes remaining to be copied in the memory copy in total.
    • the value of Xs is written back with the lowest address that has not been copied from.
    • the value of Xd is written back with the lowest address that has not been copied to.
• If the copy is in the backward direction (PSTATE.N == 1), then:
  • Xs holds the highest address that the copy is copied from +1.
  • Xd holds the highest address that the copy is copied to +1.
  • At the end of the instruction:
    • the value of Xn is written back with the number of bytes remaining to be copied in the memory copy in total.
    • the value of Xs is written back with the highest address that has not been copied from +1.
    • the value of Xd is written back with the highest address that has not been copied to +1.

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

• Xn is treated as a signed 64-bit number.
• If the copy is in the forward direction (Xn is a negative number), then:
  • Xn holds -1* the number of bytes remaining to be copied in the memory copy in total.
  • Xs holds the lowest address that the copy is copied from -Xn.
  • Xd holds the lowest address that the copy is made to -Xn.
  • At the end of the instruction, the value of Xn is written back with 0.
• If the copy is in the backward direction (Xn is a positive number), then:
  • Xn holds the number of bytes remaining to be copied in the memory copy in total.
  • Xs holds the highest address that the copy is copied from -Xn+1.
  • Xd holds the highest address that the copy is copied to -Xn+1.
  • At the end of the instruction, the value of Xn is written back with 0.

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

• Xn holds the number of bytes to be copied in the memory copy in total.
• If the copy is in the forward direction (PSTATE.N == 0), then:
  • Xs holds the lowest address that the copy is copied from.
  • Xd holds the lowest address that the copy is copied to.
  • At the end of the instruction:
    • the value of Xn is written back with 0.
    • the value of Xs is written back with the lowest address that has not been copied from.
    • the value of Xd is written back with the lowest address that has not been copied to.
• If the copy is in the backward direction (PSTATE.N == 1), then:
  • Xs holds the highest address that the copy is copied from +1.
  • Xd holds the highest address that the copy is copied to +1.
  • At the end of the instruction:
    • the value of Xn is written back with 0.
    • the value of Xs is written back with the highest address that has not been copied from +1.
    • the value of Xd is written back with the highest address that has not been copied to +1.

Explicit Memory Write effects produced by the instruction behave as if the instruction was executed at EL0 if the Effective value of PSTATE.UAO is 0 and either:

• The instruction is executed at EL1.
• The instruction is executed at EL2 when the Effective value of HCR_EL2.{E2H, TGE} is {1, 1}.

Otherwise, the Explicit Memory Write effects operate with the restrictions determined by the Exception level at which the instruction is executed.

Integer
(FEAT_MOPS)

if !IsFeatureImplemented(FEAT_MOPS) || sz != '00' then UNDEFINED; CPYParams memcpy; memcpy.d = UInt(Rd); memcpy.s = UInt(Rs); memcpy.n = UInt(Rn); constant bits(4) options = op2; constant boolean rnontemporal = options<3> == '1'; constant boolean wnontemporal = options<2> == '1'; case op1 of when '00' memcpy.stage = MOPSStage_Prologue; when '01' memcpy.stage = MOPSStage_Main; when '10' memcpy.stage = MOPSStage_Epilogue; otherwise SEE "Memory Copy and Memory Set";

Assembler Symbols