LASTA (scalar)
Extract element after last to general-purpose register
If there is an active element then extract the element after the last active element modulo the number of elements from the final source vector register. If there are no active elements, extract element zero. Then zero-extend and place the extracted element in the destination general-purpose register.
Green
True
0
0
0
0
0
1
0
1
1
0
0
0
0
0
1
0
1
LASTA <R><d>, <Pg>, <Zn>.<T>
if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then UNDEFINED;
constant integer esize = 8 << UInt(size);
constant integer rsize = if esize < 64 then 32 else 64;
constant integer g = UInt(Pg);
constant integer n = UInt(Zn);
constant integer d = UInt(Rd);
constant boolean isBefore = FALSE;
<R>
Is a width specifier,
<d>
Is the number [0-30] of the destination general-purpose register or the name ZR (31), encoded in the "Rd" 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,
size
<T>
00
B
01
H
10
S
11
D
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) operand = Z[n, VL];
bits(rsize) result;
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;
result = ZeroExtend(Elem[operand, last, esize], rsize);
X[d, rsize] = result;