Lookup table read with 2-bit indexes (single)
This instruction copies 8-bit, 16-bit or 32-bit elements from ZT0 to one destination vector using packed 2-bit indices from a segment of the source vector register. A segment corresponds to a portion of the source vector that is consumed in order to fill the destination vector. The segment is selected by the vector segment index modulo the total number of segments.
This instruction is unpredicated.
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | i4 | size | 0 | 0 | Zn | Zd | ||||||||||||
| opc2 | |||||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_SME2) then EndOfDecode(Decode_UNDEF); end; if size == '11' then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let isize : integer{} = 2; let n : integer = UInt(Zn); let d : integer = UInt(Zd); let imm : integer = UInt(i4); let nreg : integer{} = 1;
| <Zd> |
Is the name of the destination scalable vector register, encoded in the "Zd" field. |
| <T> |
Is the size specifier,
encoded in
|
| <Zn> |
Is the name of the source scalable vector register, encoded in the "Zn" field. |
| <index> |
Is the vector segment index, in the range 0 to 15, encoded in the "i4" field. |
CheckStreamingSVEEnabled(); CheckSMEZT0Enabled(); let VL : integer{} = CurrentVL(); let elements : integer = VL DIV esize; let segments : integer = (esize DIV (isize * nreg)) as integer{1, 2, 4, 8, 16}; let segment : integer = imm MOD segments; let indexes : bits(VL) = Z{}(n); let dst : integer = d; let table : bits(512) = ZT0{}(); for r = 0 to nreg-1 do let base : integer = (segment * nreg + r) * elements; var result : bits(VL); for e = 0 to elements-1 do let index : integer = UInt(indexes[(base+e)*:isize]); result[e*:esize] = table[index*:32][esize-1:0]; end; Z{VL}(dst+r) = result; end;
This instruction is a data-independent-time instruction as described in About PSTATE.DIT.
2026-03_rel 2026-03-26 20:48:11
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