SETPN, SETMN, SETEN

Memory Set, 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: SETPN, then SETMN, and then SETEN.

SETPN performs some preconditioning of the arguments suitable for using the SETMN instruction, and performs an IMPLEMENTATION DEFINED amount of the memory set. SETMN performs an IMPLEMENTATION DEFINED amount of the memory set. SETEN performs the last part of the memory set.

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

After execution of SETPN, 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 SETPN, 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 SETMN, 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 holds the lowest address that the set 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 set in the memory set in total.

For SETMN, 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 lowest 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 lowest address that has not been set.

For SETEN, 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 holds the lowest address that the set is made to -Xn.
• At the end of the instruction, the value of Xn is written back with 0.

For SETEN, 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 lowest 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 lowest address that has not been set.

Integer
(FEAT_MOPS)

if !IsFeatureImplemented(FEAT_MOPS) || sz != '00' then UNDEFINED; SETParams memset; memset.d = UInt(Rd); memset.s = UInt(Rs); memset.n = UInt(Rn); bits(2) options = op2<1:0>; boolean nontemporal = options<1> == '1'; case op2<3:2> of when '00' memset.stage = MOPSStage_Prologue; when '01' memset.stage = MOPSStage_Main; when '10' memset.stage = MOPSStage_Epilogue; otherwise UNDEFINED;

Assembler Symbols