Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

## WHILELS (predicate pair)

While incrementing unsigned scalar lower or same as scalar (pair of predicates)

Generate a pair of predicates that starting from the lowest numbered element of the pair is true while the incrementing value of the first, unsigned scalar operand is lower or same as the second scalar operand and false thereafter up to the highest numbered element of the pair.

If the second scalar operand is equal to the maximum unsigned integer value then a condition which includes an equality test can never fail and the result will be an all-true predicate.

The full width of the scalar operands is significant for the purposes of comparison, and the full width first operand is incremented by one for each destination predicate element, irrespective of the predicate result element size. The first general-purpose source register is not itself updated.

The lower-numbered elements are placed in the first predicate destination register, and the higher-numbered elements in the second predicate destination register. Sets the First (N), None (Z), !Last (C) condition flags based on the predicate result, and the V flag to zero.

### SVE2
(FEAT_SVE2p1)

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 | 1 | 0 | 0 | 1 | 0 | 1 | size | 1 | Rm | 0 | 1 | 0 | 1 | 1 | 1 | Rn | 1 | Pd | 1
|  |  |  |  | U | lt |  |  |  | eq

####

WHILELS { <Pd1>.<T>, <Pd2>.<T> }, <Xn>, <Xm>

if !HaveSME2() && !HaveSVE2p1() then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer rsize = 64; integer n = UInt(Rn); integer m = UInt(Rm); integer d0 = UInt(Pd:'0'); integer d1 = UInt(Pd:'1'); boolean unsigned = TRUE; SVECmp op = Cmp_LE;

### Assembler Symbols

<Pd1> | Is the name of the first destination scalable predicate register, encoded as "Pd" times 2.

<T> | Is the size specifier, encoded in size:
size | <T>
--- | ---
00 | B
01 | H
10 | S
11 | D

<Pd2> | Is the name of the second destination scalable predicate register, encoded as "Pd" times 2 plus 1.

<Xn> | Is the 64-bit name of the first source general-purpose register, encoded in the "Rn" field.

<Xm> | Is the 64-bit name of the second source general-purpose register, encoded in the "Rm" field.

### Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = VL DIV esize; bits(PL*2) mask = Ones(PL*2); bits(rsize) operand1 = X[n, rsize]; bits(rsize) operand2 = X[m, rsize]; bits(PL*2) result; boolean last = TRUE; constant integer psize = esize DIV 8; for e = 0 to (elements*2)-1 boolean cond; case op of when Cmp_LT cond = (Int(operand1, unsigned) < Int(operand2, unsigned)); when Cmp_LE cond = (Int(operand1, unsigned) <= Int(operand2, unsigned)); last = last && cond; bit pbit = if last then '1' else '0'; Elem[result, e, psize] = ZeroExtend(pbit, psize); operand1 = operand1 + 1; PSTATE.<N,Z,C,V> = PredTest(mask, result, esize); P[d0, PL] = result<PL-1:0>; P[d1, PL] = result<PL*2-1:PL>;

### Operational information

If PSTATE.DIT is 1:

- The execution time of this instruction is independent of:
  - The values of the data supplied in any of its registers.
  - The values of the NZCV flags.
- The response of this instruction to asynchronous exceptions does not vary based on:
  - The values of the data supplied in any of its registers.
  - The values of the NZCV flags.

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: isa v33.64, AdvSIMD v29.12, pseudocode v2023-06_rel, sve v2023-06_rel ; Build timestamp: 2023-07-04T19:42

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