PTRUE (predicate)

Initialise predicate from named constraint

Set elements of the destination predicate to true if the element number satisfies the named predicate constraint, or to false otherwise. If the constraint specifies more elements than are available at the current vector length then all elements of the destination predicate are set to false.

The named predicate constraint limits the number of active elements in a single predicate to:

  • A fixed number (VL1 to VL256)
  • The largest power of two (POW2)
  • The largest multiple of three or four (MUL3 or MUL4)
  • All available, implicitly a multiple of two (ALL).

    • Unspecified or out of range constraint encodings generate an empty predicate or zero element count rather than Undefined Instruction exception. Does not set the condition flags.

    Encoding: Not setting the condition flags

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

    313029282726252423222120191817161514131211109876543210
    001001010110001110000
    sizeSpatternPd

    PTRUE <Pd>.<T>{, <pattern>}

    Decoding algorithm

    if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer d = UInt(Pd);
constant boolean setflags = FALSE;
constant bits(5) pat = pattern;

    Operation

    CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant integer count = DecodePredCount(pat, esize);
bits(PL) result;
constant integer psize = esize DIV 8;

for e = 0 to elements-1
    constant bit pbit = if e < count then '1' else '0';
    Elem[result, e, psize] = ZeroExtend(pbit, psize);

if setflags then
    PSTATE. = PredTest(result, result, esize);
P[d, PL] = result;

    Explanations

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

    Operational Notes

    If PSTATE.DIT is 1: