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LD1ROB (scalar plus immediate)

Contiguous load and replicate thirty-two bytes (immediate index).

Load thirty-two contiguous bytes to elements of a 256-bit (octaword) vector from the memory address generated by a 64-bit scalar base address and immediate index that is a multiple of 32 in the range -256 to +224 added to the base address.

Inactive elements will not read Device memory or signal a fault, and are set to zero.

The resulting 256-bit vector is then replicated to fill the destination vector. The instruction requires that the current vector length is at least 256 bits, and if the current vector length is not an integer multiple of 256 bits then the trailing bits in the destination vector are set to zero.

Only the first thirty-two predicate elements are used and higher numbered predicate elements are ignored.

ID_AA64ZFR0_EL1.F64MM indicates whether this instruction is implemented.

313029282726252423222120191817161514131211109876543210
101001000010imm4001PgRnZt
msz<1>msz<0>ssz

SVE

LD1ROB { <Zt>.B }, <Pg>/Z, [<Xn|SP>{, #<imm>}]

if !HaveSVEFP64MatMulExt() then UNDEFINED;
integer t = UInt(Zt);
integer n = UInt(Rn);
integer g = UInt(Pg);
integer esize = 8;
integer offset = SInt(imm4);

Assembler Symbols

<Zt>

Is the name of the scalable vector register to be transferred, encoded in the "Zt" field.

<Pg>

Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Xn|SP>

Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.

<imm>

Is the optional signed immediate byte offset, a multiple of 32 in the range -256 to 224, defaulting to 0, encoded in the "imm4" field.

Operation

CheckSVEEnabled();
if VL < 256 then UNDEFINED;
integer elements = 256 DIV esize;
bits(64) base;
bits(64) addr;
bits(PL) mask = P[g]; // low bits only
bits(256) result;
constant integer mbytes = esize DIV 8;

if n == 31 then
    if LastActiveElement(mask, esize) >= 0 || 
          ConstrainUnpredictableBool(Unpredictable_CHECKSPNONEACTIVE) then 
        CheckSPAlignment();
    if HaveMTEExt() then SetTagCheckedInstruction(FALSE);
    base = SP[];
else
    if HaveMTEExt() then SetTagCheckedInstruction(TRUE);
    base = X[n];

addr = base + offset * 32;
for e = 0 to elements-1
    if ElemP[mask, e, esize] == '1' then
        Elem[result, e, esize] = Mem[addr, mbytes, AccType_NORMAL];
    else
        Elem[result, e, esize] = Zeros();
    addr = addr + mbytes;

Z[t] = ZeroExtend(Replicate(result, VL DIV 256), VL);