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DECP (scalar)

Decrement scalar by count of true predicate elements.

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

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00100101size1011011000100PmRdn
D

DECP <Xdn>, <Pm>.<T>

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

Assembler Symbols

<Xdn>

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

<Pm>

Is the name of the source scalable predicate register, encoded in the "Pm" field.

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

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(64) operand1 = X[dn];
bits(PL) operand2 = P[m];
integer count = 0;

for e = 0 to elements-1
    if ElemP[operand2, e, esize] == '1' then
        count = count + 1;

X[dn] = operand1 - count;
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