tbx

Table Lookup Extension (SVE)

TBX <Zd>.<T>, <Zn>.<T>, <Zm>.<T>

Vector table extension (SVE version of TBX).

Pseudocode Operation

No pseudocode available.

Encoding

Binary Layout

00000101

31:24

size

23:22

20:16

00101

15:11

9:5

4:0

Format SVE Permute

Opcode 0x05202C00

Extension SVE

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x0E001000	TBX <Vd>.<Ta>, { <Vn>.16B }, <Vm>.<Ta>	A64	0 \| Q \| 001110 \| 00 \| 0 \| Rm \| 0 \| 00 \| 1 \| 00 \| Rn \| Rd
0x0E003000	TBX <Vd>.<Ta>, { <Vn>.16B, <Vn+1>.16B }, <Vm>.<Ta>	A64	0 \| Q \| 001110 \| 00 \| 0 \| Rm \| 0 \| 01 \| 1 \| 00 \| Rn \| Rd
0x0E005000	TBX <Vd>.<Ta>, { <Vn>.16B, <Vn+1>.16B, <Vn+2>.16B }, <Vm>.<Ta>	A64	0 \| Q \| 001110 \| 00 \| 0 \| Rm \| 0 \| 10 \| 1 \| 00 \| Rn \| Rd
0x0E007000	TBX <Vd>.<Ta>, { <Vn>.16B, <Vn+1>.16B, <Vn+2>.16B, <Vn+3>.16B }, <Vm>.<Ta>	A64	0 \| Q \| 001110 \| 00 \| 0 \| Rm \| 0 \| 11 \| 1 \| 00 \| Rn \| Rd
0x05202C00	TBX <Zd>.<T>, <Zn>.<T>, <Zm>.<T>	A64	00000101 \| size \| 1 \| Zm \| 00101 \| 1 \| Zn \| Zd

Description

Reads each element of the second source (index) vector and uses its value to select an indexed element from a table of elements in the first source vector, and places the indexed 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 the corresponding destination vector element is left unchanged. Since the index values can select any element in a vector this operation is not naturally vector length agnostic.

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer PL = VL DIV 8;
constant integer elements = VL DIV esize;
bits(VL) operand1 = Z[n, VL];
bits(VL) operand2 = Z[m, VL];
bits(VL) result = Z[d, VL];

for e = 0 to elements-1
    integer element2 = UInt(Elem[operand2, e, esize]);
    if element2 < elements then
        Elem[result, e, esize] = Elem[operand1, element2, esize];

Z[d, VL] = result;

tbx