Floating-point reversed subtract from immediate (predicated)
This instruction reverse subtracts from an immediate each active floating-point element of the source vector, and destructively places the results in the corresponding elements of the source vector. The immediate may take the value +0.5 or +1.0 only. Inactive elements in the destination vector register remain unmodified.
| 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 | 1 | 0 | 0 | 1 | 0 | 1 | size | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 0 | Pg | 0 | 0 | 0 | 0 | i1 | Zdn | |||||||
| opc | |||||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; if size == '00' then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let g : integer = UInt(Pg); let dn : integer = UInt(Zdn); let imm : bits(esize) = if i1 == '0' then FPPointFive{esize}('0') else FPOne{esize}('0');
| <Zdn> |
Is the name of the 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. |
| <const> |
Is the floating-point immediate value,
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 operand1 : bits(VL) = Z{}(dn); var result : bits(VL); for e = 0 to elements-1 do let element1 : bits(esize) = operand1[e*:esize]; if ActivePredicateElement{PL}(mask, e, esize) then result[e*:esize] = FPSub{esize}(imm, element1, FPCR()); else result[e*:esize] = element1; end; end; Z{VL}(dn) = result;
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:
2026-03_rel 2026-03-26 20:48:11
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