Subtract pairwise
This instruction subtracts pairs of adjacent elements within each source vector, and destructively places the interleaved results in the first source vector.
| 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 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | size | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | Pg | Zm | Zdn | |||||||||||
| opc | U | ||||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_SVE2p3) && !IsFeatureImplemented(FEAT_SME2p3) then EndOfDecode(Decode_UNDEF); constant integer esize = 8 << UInt(size); constant integer g = UInt(Pg); constant integer m = UInt(Zm); constant integer dn = UInt(Zdn);
| <Zdn> |
Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field. |
| <T> |
Is the size specifier,
encoded in
|
| <Pg> |
Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field. |
| <Zm> |
Is the name of the second source scalable vector register, encoded in the "Zm" field. |
CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; constant bits(PL) mask = P[g, PL]; constant bits(VL) operand1 = Z[dn, VL]; constant bits(VL) operand2 = if AnyActiveElement(mask, esize) then Z[m, VL] else Zeros(VL); bits(VL) result; integer element1; integer element2; for e = 0 to elements-1 if !ActivePredicateElement(mask, e, esize) then Elem[result, e, esize] = Elem[operand1, e, esize]; else if IsEven(e) then element1 = UInt(Elem[operand1, e + 0, esize]); element2 = UInt(Elem[operand1, e + 1, esize]); else element1 = UInt(Elem[operand2, e - 1, esize]); element2 = UInt(Elem[operand2, e + 0, esize]); constant integer res = element1 - element2; Elem[result, e, esize] = res<esize-1:0>; Z[dn, VL] = result;
This instruction is a data-independent-time instruction as described in About PSTATE.DIT.
This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is CONSTRAINED UNPREDICTABLE:
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