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.

Note

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.

Note

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

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.

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);
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;

CheckMOPSEnabled();

if (memset.s == memset.n || memset.s == memset.d || memset.n == memset.d || memset.d == 31 || memset.n == 31) then
    Constraint c = ConstrainUnpredictable(Unpredictable_MOPSOVERLAP31);
    assert c IN {Constraint_UNDEF, Constraint_NOP};
    case c of
        when Constraint_UNDEF UNDEFINED;
        when Constraint_NOP   EndOfInstruction();

Assembler Symbols

bits(8) data = X[memset.s, 8];
integer B;

memset.is_setg = TRUE;
memset.nzcv = PSTATE.<N,Z,C,V>;
memset.toaddress = X[memset.d, 64];
if memset.stage == MOPSStage_Prologue then
    memset.setsize = UInt(X[memset.n, 64]);
else
    memset.setsize = SInt(X[memset.n, 64]);
memset.implements_option_a = SETGOptionA();

boolean privileged = if options<0> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0;

AccessDescriptor accdesc = CreateAccDescSTGMOPS(privileged, nontemporal);

if memset.stage == MOPSStage_Prologue then
    if memset.setsize > 0x7FFFFFFFFFFFFFF0 then
        memset.setsize = 0x7FFFFFFFFFFFFFF0;

    if ((memset.setsize != 0 && !IsAligned(memset.toaddress, TAG_GRANULE)) || !IsAligned(memset.setsize<63:0>, TAG_GRANULE)) then
        AArch64.Abort(memset.toaddress, AlignmentFault(accdesc));

    if memset.implements_option_a then
        memset.nzcv = '0000';
        memset.toaddress = memset.toaddress + memset.setsize;
        memset.setsize = 0 - memset.setsize;
    else
        memset.nzcv = '0010';

memset.stagesetsize = MemSetStageSize(memset);

if memset.stage != MOPSStage_Prologue then
    CheckMemSetParams(memset, options);

    if ((memset.setsize != 0 && !IsAligned(memset.toaddress, TAG_GRANULE)) || !IsAligned(memset.setsize<63:0>, TAG_GRANULE)) then
        AArch64.Abort(memset.toaddress, AlignmentFault(accdesc));

integer tagstep;
bits(4) tag;
bits(64) tagaddr;
AddressDescriptor memaddrdesc;
PhysMemRetStatus memstatus;
integer memory_set;
boolean fault = FALSE;

if memset.implements_option_a then
    while memset.stagesetsize < 0 && !fault do
        // IMP DEF selection of the block size that is worked on. While many
        // implementations might make this constant, that is not assumed.
        B = SETSizeChoice(memset, 16);
        assert B <= -1 * memset.stagesetsize && B<3:0> == '0000';

        (memory_set, memaddrdesc, memstatus) = MemSetBytes(memset.toaddress + memset.setsize, data, B, accdesc);

        if memory_set != B then
            fault = TRUE;
        else
            tagstep = B DIV 16;
            tag = AArch64.AllocationTagFromAddress(memset.toaddress + memset.setsize);

            while tagstep > 0 do
                tagaddr = memset.toaddress + memset.setsize + (tagstep - 1) * 16;
                AArch64.MemTag[tagaddr, accdesc] = tag;
                tagstep = tagstep - 1;

            memset.setsize = memset.setsize + B;
            memset.stagesetsize = memset.stagesetsize + B;

else
    while memset.stagesetsize > 0 && !fault do
        // IMP DEF selection of the block size that is worked on. While many
        // implementations might make this constant, that is not assumed.
        B = SETSizeChoice(memset, 16);
        assert B <= memset.stagesetsize && B<3:0> == '0000';

        (memory_set, memaddrdesc, memstatus) = MemSetBytes(memset.toaddress, data, B, accdesc);

        if memory_set != B then
            fault = TRUE;
        else
            tagstep = B DIV 16;
            tag = AArch64.AllocationTagFromAddress(memset.toaddress);
            while tagstep > 0 do
                tagaddr = memset.toaddress + (tagstep - 1) * 16;
                AArch64.MemTag[tagaddr, accdesc] = tag;
                tagstep = tagstep - 1;

            memset.toaddress = memset.toaddress + B;
            memset.setsize = memset.setsize - B;
            memset.stagesetsize = memset.stagesetsize - B;

UpdateSetRegisters(memset, fault, memory_set);

if fault then
    if IsFault(memaddrdesc) then
        AArch64.Abort(memaddrdesc.vaddress, memaddrdesc.fault);
    else
        boolean iswrite = TRUE;
        HandleExternalAbort(memstatus, iswrite, memaddrdesc, B, accdesc);

if memset.stage == MOPSStage_Prologue then
    PSTATE.<N,Z,C,V> = memset.nzcv;