FMAXP

Floating-point maximum pairwise

Compute the maximum value of each pair of adjacent floating-point elements within each source vector, and interleave the results from corresponding lanes. The interleaved result values are destructively placed in the first source vector.

When FPCR.AH is 0, the behavior is as follows for each pairwise operation:

  • Negative zero compares less than positive zero.
  • When FPCR.DN is 0, if either element is a NaN, the result is a quiet NaN.
  • When FPCR.DN is 1, if either element is a NaN, the result is Default NaN.

    • When FPCR.AH is 1, the behavior is as follows for each pairwise operation:

  • If both elements are zeros, regardless of the sign of either zero, the result is the second element.
  • If either element is a NaN, regardless of the value of FPCR.DN, the result is the second element.

    • Encoding: SVE2

    Variants: FEAT_SVE2 || FEAT_SME (FEAT_SVE2 || FEAT_SME)

    313029282726252423222120191817161514131211109876543210
    01100100010110100
    sizeopcPgZmZdn

    FMAXP <Zdn>.<T>, <Pg>/M, <Zdn>.<T>, <Zm>.<T>

    Decoding algorithm

    if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
if size == '00' then EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer g = UInt(Pg);
constant integer m = UInt(Zm);
constant integer dn = UInt(Zdn);

    Operation

    CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
constant bits(PL) mask = P[g, PL];
constant bits(VL) operand1 = Z[dn, VL];
constant bits(VL) operand2 = if AnyActiveElement(mask, esize) then Z[m, VL] else Zeros(VL);
bits(VL) result = Z[dn, VL];
bits(esize) element1;
bits(esize) element2;

for e = 0 to elements-1
    if ActivePredicateElement(mask, e, esize) then
        if IsEven(e) then
            element1 = Elem[operand1, e + 0, esize];
            element2 = Elem[operand1, e + 1, esize];
        else
            element1 = Elem[operand2, e - 1, esize];
            element2 = Elem[operand2, e + 0, esize];
        Elem[result, e, esize] = FPMax(element1, element2, FPCR);

Z[dn, VL] = result;

    Explanations

    <Zdn>: Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field.
    <T>: <Pg>: Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.
    <Zm>: Is the name of the second source scalable vector register, encoded in the "Zm" field.

    Operational Notes

    This instruction might be immediately preceded in program order by a MOVPRFX instruction. The MOVPRFX must conform to all of the following requirements, otherwise the behavior of the MOVPRFX and this instruction is CONSTRAINED UNPREDICTABLE: