CLASTB (scalar)
Conditionally extract last element to general-purpose register.
From the source vector register extract the last active element, and then zero-extend that element to destructively place in the destination and first source general-purpose register. If there are no active elements then destructively zero-extend the least significant element-size bits of the destination and first source general-purpose register.
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | size | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | Pg | Zm | Rdn |
| | | B | | | | |
if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer g = UInt(Pg);
integer dn = UInt(Rdn);
integer m = UInt(Zm);
integer csize = if esize < 64 then 32 else 64;
boolean isBefore = TRUE;
Assembler Symbols
<R> |
Is a width specifier,
encoded in
size :
|
<dn> | Is the number [0-30] of the source and destination general-purpose register or the name ZR (31), encoded in the "Rdn" field. |
<Pg> | Is the name of the governing scalable predicate register P0-P7, encoded in the "Pg" field. |
<Zm> | Is the name of the source scalable vector register, encoded in the "Zm" field. |
<T> |
Is the size specifier,
encoded in
size :
|
Operation
CheckSVEEnabled();
integer elements = VL DIV esize;
bits(PL) mask = P[g];
bits(esize) operand1 = X[dn];
bits(VL) operand2 = Z[m];
bits(csize) result;
integer last = LastActiveElement(mask, esize);
if last < 0 then
result = ZeroExtend(operand1);
else
if !isBefore then
last = last + 1;
if last >= elements then last = 0;
result = ZeroExtend(Elem[operand2, last, esize]);
X[dn] = result;
Internal version only: isa v32.03v31.05b, AdvSIMD v29.02, pseudocode v2020-03v2019-12_rc3_1, sve v2020-03_rc1v2019-12_rc3
; Build timestamp: 2020-04-15T132019-12-13T11:3302
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