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LDFF1D (scalar plus scalar)

Contiguous load first-fault doublewords to vector (scalar index).

Contiguous load with first-faulting behavior of doublewords to elements of a vector register from the memory address generated by a 64-bit scalar base and scalar index which is multiplied by 8 and added to the base address. After each element access the index value is incremented, but the index register is not updated. Inactive elements will not read Device memory or signal a fault, and are set to zero in the destination vector.



LDFF1D { <Zt>.D }, <Pg>/Z, [<Xn|SP>{, <Xm>, LSL #3}]

if !HaveSVE() then UNDEFINED;
integer t = UInt(Zt);
integer n = UInt(Rn);
integer m = UInt(Rm);
integer g = UInt(Pg);
integer esize = 64;
integer msize = 64;
boolean unsigned = TRUE;

Assembler Symbols


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


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


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


Is the optional 64-bit name of the general-purpose offset register, defaulting to XZR, encoded in the "Rm" field.


integer elements = VL DIV esize;
bits(64) base;
bits(64) addr;
bits(PL) mask = P[g];
bits(VL) result;
bits(VL) orig = Z[t];
bits(msize) data;
bits(64) offset = X[m];
constant integer mbytes = msize DIV 8;
boolean first = TRUE;
boolean fault = FALSE;
boolean faulted = FALSE;
boolean unknown = FALSE;

if HaveMTEExt() then SetNotTagCheckedInstruction(FALSE);

if n == 31 then
    base = SP[];
    base = X[n];

for e = 0 to elements-1
    if ElemP[mask, e, esize] == '1' then
        addr = base + UInt(offset) * mbytes;
        if first then
            // Mem[] will not return if a fault is detected for the first active element
            data = Mem[addr, mbytes, AccType_NORMAL];
            first = FALSE;
            // MemNF[] will return fault=TRUE if access is not performed for any reason
            (data, fault) = MemNF[addr, mbytes, AccType_CNOTFIRST];
        (data, fault) = (Zeros(msize), FALSE);

    // FFR elements set to FALSE following a supressed access/fault
    faulted = faulted || fault;
    if faulted then
        ElemFFR[e, esize] = '0';

    // Value becomes CONSTRAINED UNPREDICTABLE after an FFR element is FALSE
    unknown = unknown || ElemFFR[e, esize] == '0';
    if unknown then
        if !fault && ConstrainUnpredictableBool(Unpredictable_SVELDNFDATA) then
            Elem[result, e, esize] = Extend(data, esize, unsigned);
        elsif ConstrainUnpredictableBool(Unpredictable_SVELDNFZERO) then
            Elem[result, e, esize] = Zeros();
        else  // merge
            Elem[result, e, esize] = Elem[orig, e, esize];
        Elem[result, e, esize] = Extend(data, esize, unsigned);

    offset = offset + 1;

Z[t] = result;