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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.

It has encodings from 2 classes: High half and Low half

High half

313029282726252423222120191817161514131211109876543210
00000101001100010100000Pn0Pd

High half

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

if !HaveSVE() then UNDEFINED;
integer esize = 16;
integer n = UInt(Pn);
integer d = UInt(Pd);
boolean hi = TRUE;

Low half

313029282726252423222120191817161514131211109876543210
00000101001100000100000Pn0Pd

Low half

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

if !HaveSVE() then UNDEFINED;
integer esize = 16;
integer n = UInt(Pn);
integer d = UInt(Pd);
boolean hi = FALSE;

Assembler Symbols

<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.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(PL) operand = P[n];
bits(PL) result;

for e = 0 to elements-1
    ElemP[result, e, esize] = ElemP[operand, if hi then e + elements else e, esize DIV 2];

P[d] = result;

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.
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