Multi-vector conditional select
This instruction selects consecutive elements from the two or four first source vectors where vector select predicate elements are true, and places them in the corresponding elements of the two or four destination vectors. Where vector select predicate elements are false, the corresponding consecutive elements are selected from the two or four second source vectors and placed in the remaining elements of the destination vectors.
It has encodings from 2 classes: Two registers and Four registers
| 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 | 1 | size | 1 | Zm | 0 | 1 | 0 | 0 | PNv | Zn | 0 | Zd | 0 | ||||||||||||
if !IsFeatureImplemented(FEAT_SME2) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let n : integer = UInt(Zn::'0'); let m : integer = UInt(Zm::'0'); let d : integer = UInt(Zd::'0'); let v : integer = UInt('1'::PNv); let nreg : integer{} = 2;
| 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 | 1 | size | 1 | Zm | 0 | 1 | 1 | 0 | 0 | PNv | Zn | 0 | 0 | Zd | 0 | 0 | |||||||||
if !IsFeatureImplemented(FEAT_SME2) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let n : integer = UInt(Zn::'00'); let m : integer = UInt(Zm::'00'); let d : integer = UInt(Zd::'00'); let v : integer = UInt('1'::PNv); let nreg : integer{} = 4;
| <T> |
Is the size specifier,
encoded in
|
| <Zd2> |
Is the name of the second scalable vector register of the destination multi-vector group, encoded as "Zd" times 2 plus 1. |
| <PNv> |
Is the name of the vector select predicate register PN8-PN15, with predicate-as-counter encoding, encoded in the "PNv" field. |
| <Zn2> |
Is the name of the second scalable vector register of the first source multi-vector group, encoded as "Zn" times 2 plus 1. |
| <Zm2> |
Is the name of the second scalable vector register of the second source multi-vector group, encoded as "Zm" times 2 plus 1. |
| <Zd4> |
Is the name of the fourth scalable vector register of the destination multi-vector group, encoded as "Zd" times 4 plus 3. |
| <Zn4> |
Is the name of the fourth scalable vector register of the first source multi-vector group, encoded as "Zn" times 4 plus 3. |
| <Zm4> |
Is the name of the fourth scalable vector register of the second source multi-vector group, encoded as "Zm" times 4 plus 3. |
CheckStreamingSVEEnabled(); let VL : integer{} = CurrentVL(); let PL : integer{} = VL DIV 8; let elements : integer = VL DIV esize; var results : array[[4]] of bits(VL); let pred : bits(PL) = P{}(v); let mask : bits(PL * nreg) = CounterToPredicate{}(pred[15:0]); for r = 0 to nreg-1 do let operand1 : bits(VL) = Z{}(n+r); let operand2 : bits(VL) = Z{}(m+r); for e = 0 to elements-1 do if ActivePredicateElement{PL*nreg}(mask, r * elements + e, esize) then results[[r]][e*:esize] = operand1[e*:esize]; else results[[r]][e*:esize] = operand2[e*:esize]; end; end; end; for r = 0 to nreg-1 do Z{VL}(d+r) = results[[r]]; 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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