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DECP (scalar)

Decrement scalar by active predicate element count.

Counts the number of active elements in the source predicate and then uses the result to decrement the scalar destination.



DECP <Xdn>, <Pg>.<T>

if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer g = UInt(Pg);
integer dn = UInt(Rdn);

Assembler Symbols


Is the 64-bit name of the source and destination general-purpose register, encoded in the "Rdn" field.


Is the name of the governing scalable predicate register, encoded in the "Pg" field.

<T> Is the size specifier, encoded in size:
size <T>
00 B
01 H
10 S
11 D


integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(64) operand = X[dn];
integer count = 0;

for e = 0 to elements-1
    if ElemP[mask, e, esize] == '1' then
        count = count + 1;

X[dn] = operand - count;