Programmable table lookup in one or two vector table (zeroing)
Reads each element of the second source (index) vector and uses its value to select an indexed element from a table of elements consisting of one or two consecutive vector registers, where the first or only vector holds the lower numbered elements, and places the indexed table element in the destination vector element corresponding to the index vector element. If an index value is greater than or equal to the number of vector elements then it places zero in the corresponding destination vector element.
Since the index values can select any element in a vector this operation is not naturally vector length agnostic.
It has encodings from 2 classes: SVE and SVE2
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 | Zm | 0 | 0 | 1 | 1 | 0 | 0 | Zn | Zd |
if !HaveSVE() && !HaveSME() then UNDEFINED; integer esize = 8 << UInt(size); integer n = UInt(Zn); integer m = UInt(Zm); integer d = UInt(Zd); boolean double_table = FALSE;
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 | Zm | 0 | 0 | 1 | 0 | 1 | 0 | Zn | Zd |
if !HaveSVE2() && !HaveSME() then UNDEFINED; integer esize = 8 << UInt(size); integer n = UInt(Zn); integer m = UInt(Zm); integer d = UInt(Zd); boolean double_table = TRUE;
<Zd> |
Is the name of the destination scalable vector register, encoded in the "Zd" field. |
<T> |
Is the size specifier,
encoded in
|
<Zn> |
Is the name of the first source scalable vector register, encoded in the "Zn" field. |
<Zn1> |
Is the name of the first scalable vector register of a multi-vector sequence, encoded in the "Zn" field. |
<Zn2> |
Is the name of the second scalable vector register of a multi-vector sequence, encoded in the "Zn" field. |
<Zm> |
Is the name of the second source scalable vector register, encoded in the "Zm" field. |
CheckSVEEnabled(); integer elements = VL DIV esize; bits(VL) indexes = Z[m]; bits(VL) result; integer table_size = if double_table then VL*2 else VL; integer table_elems = table_size DIV esize; bits(table_size) table; if double_table then bits(VL) top = Z[(n + 1) MOD 32]; bits(VL) bottom = Z[n]; table = (top:bottom)<table_size-1:0>; else table = Z[n]; for e = 0 to elements-1 integer idx = UInt(Elem[indexes, e, esize]); Elem[result, e, esize] = if idx < table_elems then Elem[table, idx, esize] else Zeros(); Z[d] = result;
If FEAT_SVE2 is enabled or FEAT_SME is enabled, then when PSTATE.DIT is 1:
Internal version only: isa v33.11seprel, AdvSIMD v29.05, pseudocode v2021-09_rel, sve v2021-09_rc3d ; Build timestamp: 2021-10-06T11:41
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