CPYFPT, CPYFMT, CPYFET

Memory Copy Forward-only, 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: CPYFPT, then CPYFMT, and then CPYFET.

CPYFPT performs some preconditioning of the arguments suitable for using the CPYFMT instruction, and performs an implementation defined amount of the memory copy. CPYFMT performs an implementation defined amount of the memory copy. CPYFET 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.

The memory copy performed by these instructions is in the forward direction only, so the instructions are suitable for a memory copy only where there is no overlap between the source and destination locations, or where the source address is greater than the destination address.

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 CPYFPT, option A (which results in encoding PSTATE.C = 0):

• If Xn<63> == 1, the copy size is saturated to 0x7FFFFFFFFFFFFFFF.
• 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.
• PSTATE.{N,Z,V} are set to {0,0,0}.

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

• If Xn<63> == 1, the copy size is saturated to 0x7FFFFFFFFFFFFFFF.
• 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}.

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

• Xn is treated as a signed 64-bit number and holds -1* the number of bytes remaining to be copied in the memory copy in total.
• Xs + Xn holds the first address that the copy is copied from.
• Xd + Xn holds the first address that the copy is made to.
• 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.

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

• Xn holds the number of bytes remaining to be copied in the memory copy in total.
• Xs holds the first address that the copy is copied from.
• Xd holds the first 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 first address that has not been copied from.
  • the value of Xd is written back with the first address that has not been copied to.

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

• Xn is treated as a signed 64-bit number and holds -1* the number of bytes remaining to be copied in the memory copy in total.
• Xs + Xn holds the first address that the copy is copied from.
• Xd + Xn holds the first address that the copy is made to.
• At the end of the instruction, the value of Xn is written back with 0.

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

• Xn holds the number of bytes remaining to be copied in the memory copy in total.
• Xs holds the first address that the copy is copied from.
• Xd holds the first 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 first address that has not been copied from.
  • the value of Xd is written back with the first address that has not been copied to.

Integer
(FEAT_MOPS)

if !HaveFeatMOPS() then UNDEFINED; if sz != '00' then UNDEFINED; integer d = UInt(Rd); integer s = UInt(Rs); integer n = UInt(Rn); bits(4) options = op2; 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"; if d == s || s == n || d == n then UNDEFINED; if d == 31 || s == 31 || n == 31 then UNDEFINED;