Extract last element to general-purpose register
This instruction extracts the Last active element to a general-purpose register. If there is an Active element, the Last active element from the final source vector register is extracted. If there are no Active elements, the highest-numbered element is extracted. Then the extracted element is zero-extended and placed in the destination general-purpose register.
| 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 |
| 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | size | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | Pg | Zn | Rd | |||||||||||
| B | |||||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let rsize : integer{} = if esize < 64 then 32 else 64; let g : integer = UInt(Pg); let n : integer = UInt(Zn); let d : integer = UInt(Rd); let isBefore : boolean = TRUE;
| <R> |
Is a width specifier,
encoded in
|
| <d> |
Is the number [0-30] of the destination general-purpose register or the name ZR (31), encoded in the "Rd" field. |
| <Pg> |
Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field. |
| <Zn> |
Is the name of the source scalable vector register, encoded in the "Zn" field. |
| <T> |
Is the size specifier,
encoded in
|
CheckSVEEnabled(); let VL : integer{} = CurrentVL(); let PL : integer{} = VL DIV 8; let elements : integer = VL DIV esize; let mask : bits(PL) = P{}(g); let operand : bits(VL) = Z{}(n); var result : bits(rsize); var last : integer = LastActiveElement{PL}(mask, esize); if isBefore then if last < 0 then last = elements - 1; end; else last = last + 1; if last >= elements then last = 0; end; end; result = ZeroExtend{rsize}(operand[last*:esize]); X{rsize}(d) = result;
If FEAT_SME is implemented and the PE is in Streaming SVE mode, then any subsequent instruction which is dependent on the general-purpose register written by this instruction might be significantly delayed.
2026-03_rel 2026-03-26 20:48:11
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