WHILELT (predicate as counter)

Generate a predicate for a group of two or four vectors that starting from the lowest numbered element of the group 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 group.

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 predicate result is placed in the predicate destination register using the predicate-as-counter encoding. 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 !HaveSME2() && !HaveSVE2p1() then UNDEFINED; constant integer esize = 8 << UInt(size); constant integer rsize = 64; integer n = UInt(Rn); integer m = UInt(Rm); integer d = UInt('1':PNd); boolean unsigned = FALSE; boolean invert = FALSE; SVECmp op = Cmp_LT; integer width = 2 << UInt(vl);

Assembler Symbols

<PNd>

Is the name of the destination scalable predicate register PN8-PN15, with predicate-as-counter encoding, encoded in the "PNd" field.

<T>

Is the size specifier, encoded in size:

size	<T>
00	B
01	H
10	S
11	D

<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.

<vl>

Is the vl specifier, encoded in vl:

vl	<vl>
0	VLx2
1	VLx4

Operation

if HaveSVE2p1() then CheckSVEEnabled(); else CheckStreamingSVEEnabled(); constant integer VL = CurrentVL; constant integer PL = VL DIV 8; constant integer elements = width * (VL DIV esize); bits(rsize) operand1 = X[n, rsize]; bits(rsize) operand2 = X[m, rsize]; bits(PL) result; boolean last = TRUE; integer count = 0; for e = 0 to elements-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; if last then count = count + 1; operand1 = operand1 + 1; result = EncodePredCount(esize, elements, count, invert, PL); PSTATE.<N,Z,C,V> = PredCountTest(elements, count, invert); P[d, PL] = result;

Internal version only: aarchmrs v2023-12_rel, pseudocode v2023-12_rel, sve v2023-12_rel ; Build timestamp: 2023-12-15T16:46

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	vl	0	0	1	Rn					1	0	PNd
																				U	lt							eq