SETGPT, SETGMT, SETGET

Memory set with tag setting, unprivileged

These instructions perform a memory set using the value in the bottom byte of the source register and store an Allocation Tag to memory for each Tag Granule written. The Allocation Tag is calculated from the Logical Address Tag in the register which holds the first address that the set is made to. The prologue, main, and epilogue instructions are expected to be run in succession and to appear consecutively in memory: SETGPT, then SETGMT, and then SETGET.

SETGPT performs some preconditioning of the arguments suitable for using the SETGMT instruction, and performs an IMPLEMENTATION DEFINED amount of the memory set. SETGMT performs an IMPLEMENTATION DEFINED amount of the memory set. SETGET 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 SETGPT, option A (which results in encoding PSTATE.C = 0):

• If Xn<63> == 1, the set size is saturated to 0x7FFFFFFFFFFFFFF0.
• 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 SETGPT, option B (which results in encoding PSTATE.C = 1):

• If Xn<63> == 1, the copy size is saturated to 0x7FFFFFFFFFFFFFF0.
• 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 SETGMT, 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* number of bytes remaining to be set in the memory set in total.

For SETGMT, 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 SETGET, 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 SETGET, 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.

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) || !IsFeatureImplemented(FEAT_MTE) || sz != '00' then UNDEFINED; SETParams memset; memset.d = UInt(Rd); memset.s = UInt(Rs); memset.n = UInt(Rn); constant bits(2) options = op2<1:0>; constant 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