TBXQ

Programmable table lookup within each quadword vector segment (merging)

For each 128-bit destination vector segment, reads each element of the corresponding second source (index) vector segment and uses its value to select an indexed element from the corresponding first source (table) vector segment. The indexed table element is placed in the element of the destination vector that corresponds to the index vector element. If an index value is greater than or equal to the number of elements in a 128-bit vector segment then the corresponding destination vector element is left unchanged. This instruction is unpredicated.

Encoding: SVE2

Variants: FEAT_SVE2p1 || FEAT_SME2p1 (FEAT_SVE2p1 || FEAT_SME2p1)

313029282726252423222120191817161514131211109876543210
000001011001101
sizeZmZnZd

TBXQ <Zd>.<T>, <Zn>.<T>, <Zm>.<T>

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE2p1) && !IsFeatureImplemented(FEAT_SME2p1) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer n = UInt(Zn);
constant integer m = UInt(Zm);
constant integer d = UInt(Zd);

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer segments = VL DIV 128;
constant integer elements = 128 DIV esize;
constant bits(VL) operand1 = Z[n, VL];
constant bits(VL) operand2 = Z[m, VL];
bits(VL) result = Z[d, VL];

for s = 0 to segments-1
    for e = 0 to elements-1
        constant integer idx = UInt(Elem[operand2, s * elements + e, esize]);
        if idx < elements then
            Elem[result, s * elements + e, esize] = Elem[operand1, s * elements + idx, esize];

Z[d, VL] = result;

Explanations

<Zd>: Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T>: <Zn>: Is the name of the first source scalable vector register, encoded in the "Zn" field.
<Zm>: Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operational Notes

If PSTATE.DIT is 1: