setm

Memory Set (Main)

SETM [<Xd>]!, <Xn>!, <Xs>

Memory Set Main.

Pseudocode Operation

No pseudocode available.

Encoding

Binary Layout

31:30

011

29:27

25:24

23:22

20:16

0100

15:12

11:10

9:5

4:0

Format FEAT_MOPS

Opcode 0x19C04400

Extension FEAT_MOPS

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x19C04400	SETM [<Xd>]!, <Xn>!, <Xs>		A64		sz \| 011 \| 0 \| 01 \| 11 \| 0 \| Rs \| 0100 \| 01 \| Rn \| Rd

Description

Memory Set. 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: SETP, then SETM, and then SETE. SETP performs some preconditioning of the arguments suitable for using the SETM instruction, and performs an IMPLEMENTATION DEFINED amount of the memory set. SETM performs an IMPLEMENTATION DEFINED amount of the memory set. SETE 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 SETP, option A (which results in encoding PSTATE.C = 0): After execution of SETP, option B (which results in encoding PSTATE.C = 1): For SETM, option A (encoded by PSTATE.C = 0), the format of the arguments is: For SETM, option B (encoded by PSTATE.C = 1), the format of the arguments is: For SETE, option A (encoded by PSTATE.C = 0), the format of the arguments is: For SETE, option B (encoded by PSTATE.C = 1), the format of the arguments is:

Operation

CheckMOPSEnabled();

CheckSETConstrainedUnpredictable(memset.n, memset.d, memset.s);

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

memset.is_setg = FALSE;
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 = SETOptionA();

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

AccessDescriptor accdesc = CreateAccDescMOPS(MemOp_STORE, privileged, nontemporal);

if memset.stage == MOPSStage_Prologue then
    if memset.setsize > 0x7FFFFFFFFFFFFFFF then
        memset.setsize = 0x7FFFFFFFFFFFFFFF;

    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);

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, 1);
        assert B <= -1 * memset.stagesetsize;

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

        if memory_set != B then
            fault = TRUE;
        else
            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, 1);
        assert B <= memset.stagesetsize;

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

        if memory_set != B then
            fault = TRUE;
        else
            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;