WHILELT (predicate pair)

Generate a pair of predicates that starting from the lowest numbered element of the pair is true while the incrementing value of the first, signed scalar operand is less than the second scalar operand and false thereafter up to the highest numbered element of the pair.

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)

if !IsFeatureImplemented(FEAT_SME2) && !IsFeatureImplemented(FEAT_SVE2p1) then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer rsize = 64; constant integer n = UInt(Rn); constant integer m = UInt(Rm); constant integer d0 = UInt(Pd:'0'); constant integer d1 = UInt(Pd:'1'); constant boolean unsigned = FALSE; constant SVECmp op = Cmp_LT;

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; constant bits(PL*2) mask = Ones(PL*2); bits(rsize) operand1 = X[n, rsize]; constant 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; constant 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>;

Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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	0	1	Rn					1	Pd			0
																				U	lt										eq