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LD2D (scalar plus immediate)

Contiguous load two-doubleword structures to two vectors (immediate index).

Contiguous load two-doubleword structures, each to the same element number in two vector registers from the memory address generated by a 64-bit scalar base and an immediate index which is a multiple of 2 in the range -16 to 14 that is multiplied by the vector's in-memory size, irrespective of predication,

Each predicate element applies to the same element number in each of the two vector registers, or equivalently to the two consecutive doublewords in memory which make up each structure. Inactive elements will not cause a read from Device memory or signal a fault, and the corresponding element is set to zero in each of the two destination vector registers.

313029282726252423222120191817161514131211109876543210
101001011010imm4111PgRnZt
msz<1>msz<0>

LD2D { <Zt1>.D, <Zt2>.D }, <Pg>/Z, [<Xn|SP>{, #<imm>, MUL VL}]

if !HaveSVE() then UNDEFINED;
integer t = UInt(Zt);
integer n = UInt(Rn);
integer g = UInt(Pg);
integer esize = 64;
integer offset = SInt(imm4);
integer nreg = 2;

Assembler Symbols

<Zt1>

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

<Zt2>

Is the name of the second scalable vector register to be transferred, encoded as "Zt" plus 1 modulo 32.

<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 vector offset, a multiple of 2 in the range -16 to 14, defaulting to 0, encoded in the "imm4" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(64) base;
bits(64) addr;
bits(PL) mask = P[g];
constant integer mbytes = esize DIV 8;
array [0..1] of bits(VL) values;

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

for r = 0 to nreg-1
    Z[(t+r) MOD 32] = values[r];