SETPTN, SETMTN, SETETN

Memory Set, unprivileged and 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: SETPTN, then SETMTN, and then SETETN.

SETPTN performs some preconditioning of the arguments suitable for using the SETMTN instruction, and performs an implementation defined amount of the memory set. SETMTN performs an implementation defined amount of the memory set. SETETN performs the last part of the memory set.

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.

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

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

• If Xn<63> == 1, the set size is saturated to 0x7FFFFFFFFFFFFFFF.
• Xd holds the original Xd + saturated Xn.
• Xn holds -1* saturated Xn + an implementation defined number of bytes set.
• PSTATE.{N,Z,V} are set to {0,0,0}.

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

• If Xn<63> == 1, the copy size is saturated to 0x7FFFFFFFFFFFFFFF.
• Xd holds the original Xd + an implementation defined number of bytes set.
• Xn holds the saturated Xn – an implementation defined number of bytes set.
• PSTATE.{N,Z,V} are set to {0,0,0}.

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

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

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

• Xn holds the number of bytes remaining to be set in the memory set in total.
• Xd holds the first address that the set is made to.
• At the end of the instruction:
  • the value of Xn is written back with the number of bytes remaining to be set in the memory set in total.
  • the value of Xd is written back with the first address that has not been set.

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

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

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

• Xn holds the number of bytes remaining to be set in the memory set in total.
• Xd holds the first address that the set is made to.
• At the end of the instruction:
  • the value of Xn is written back with 0.
  • the value of Xd is written back with the first address that has not been set.

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(2) options = op2<1:0>; MOPSStage stage; case op2<3:2> of when '00' stage = MOPSStage_Prologue; when '01' stage = MOPSStage_Main; when '10' stage = MOPSStage_Epilogue; otherwise UNDEFINED; if s == n || s == d || n == d then UNDEFINED; if d == 31 || n == 31 then UNDEFINED;