PUNPKHI, PUNPKLO

Unpack and widen half of predicate

Unpack elements from the lowest or highest half of the source predicate and place in elements of twice their size within the destination predicate. This instruction is unpredicated.

Encoding: High half

Variants: FEAT_SVE || FEAT_SME (FEAT_SVE || FEAT_SME)

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	0	0	0	1	0	1	0	0	1	1	0	0	0	1	0	1	0	0	0	0	0					0
															H								Pn					Pd

PUNPKHI <Pd>.H, <Pn>.B

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 16;
constant integer n = UInt(Pn);
constant integer d = UInt(Pd);
constant boolean hi = TRUE;

Encoding: Low half

Variants: FEAT_SVE || FEAT_SME (FEAT_SVE || FEAT_SME)

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	0	0	0	1	0	1	0	0	1	1	0	0	0	0	0	1	0	0	0	0	0					0
															H								Pn					Pd

PUNPKLO <Pd>.H, <Pn>.B

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 16;
constant integer n = UInt(Pn);
constant integer d = UInt(Pd);
constant boolean hi = FALSE;

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(PL) operand = P[n, PL];
bits(PL) result;
constant integer psize = esize DIV 8;

for e = 0 to elements-1
    constant bit pbit = PredicateElement(operand, if hi then e + elements else e, esize DIV 2);
    Elem[result, e, psize] = ZeroExtend(pbit, psize);

P[d, PL] = result;

Explanations

<Pd>: Is the name of the destination scalable predicate register, encoded in the "Pd" field.
<Pn>: Is the name of the source scalable predicate register, encoded in the "Pn" field.