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LASTB (SIMD&FP scalar)

Extract last element to SIMD&FP scalar register.

If there is an active element then extract the last active element from the final source vector register. If there are no active elements, extract the highest-numbered element. Then place the extracted element in the destination SIMD&FP register.

313029282726252423222120191817161514131211109876543210
00000101size100011100PgZnVd
B
if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer g = UInt(Pg);
integer n = UInt(Zn);
integer d = UInt(Vd);
boolean isBefore = TRUE;

Assembler Symbols

<V> Is a width specifier, encoded in size:
size <V>
00 B
01 H
10 S
11 D
<d>

Is the number [0-31] of the destination SIMD&FP register, encoded in the "Vd" field.

<Pg>

Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field.

<Zn>

Is the name of the source scalable vector register, encoded in the "Zn" 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(PL) mask = P[g];
bits(VL) operand = Z[n];
integer last = LastActiveElement(mask, esize);

if isBefore then
    if last < 0 then last = elements - 1;
else
    last = last + 1;
    if last >= elements then last = 0;
V[d] = Elem[operand, last, esize];