vext

Vector Extract

VEXT<c>.8 <Qd>, <Qn>, <Qm>, #<imm>

Extracts a new vector from a pair of vectors (Sliding window).

Pseudocode Operation

combined ← (Qn << (imm * 8)) | (Qm >> ((16 - imm) * 8))
Qd ← combined[127:0]
for i = 0 to 15
  Qd[8*i+7:8*i] ← (Qn || Qm)[8*(imm+i)+7:8*(imm+i)]

Example

VEXT.8 q0, q1, q2, #16

Encoding

Binary Layout

111100101

31:23

D

22

11

21:20

Vn

19:16

Vd

15:12

imm4

11:8

N

7

0

6

M

5

0

4

Vm

3:0

 

Format NEON Extract

Opcode 0xF2B00000

Extension NEON (SIMD)

Operands

• Qd
  Destination 128-bit SIMD register
• Qn
  Low Src
• Qm
  High Src
• imm
  Byte Offset

Related

More in NEON (SIMD)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xF2B00000	VEXT{<c>}{<q>}.8 {<Dd>,} <Dn>, <Dm>, #<imm>		A32		111100101 | D | 11 | Vn | Vd | imm4 | N | 0 | M | 0 | Vm
0xF2B00040	VEXT{<c>}{<q>}.8 {<Qd>,} <Qn>, <Qm>, #<imm>		A32		111100101 | D | 11 | Vn | Vd | imm4 | N | 1 | M | 0 | Vm
0xEFB00000	VEXT{<c>}{<q>}.8 {<Dd>,} <Dn>, <Dm>, #<imm>		T32		111011111 | D | 11 | Vn | Vd | imm4 | N | 0 | M | 0 | Vm
0xEFB00040	VEXT{<c>}{<q>}.8 {<Qd>,} <Qn>, <Qm>, #<imm>		T32		111011111 | D | 11 | Vn | Vd | imm4 | N | 1 | M | 0 | Vm
0xF2B00000	VEXT{<c>}{<q>}.<size> {<Dd>,} <Dn>, <Dm>, #<imm>		A32		111100101 | D | 11 | Vn | Vd | imm4 | N | 0 | M | 0 | Vm
0xF2B00040	VEXT{<c>}{<q>}.<size> {<Qd>,} <Qn>, <Qm>, #<imm>		A32		111100101 | D | 11 | Vn | Vd | imm4 | N | 1 | M | 0 | Vm
0xEFB00000	VEXT{<c>}{<q>}.<size> {<Dd>,} <Dn>, <Dm>, #<imm>		T32		111011111 | D | 11 | Vn | Vd | imm4 | N | 0 | M | 0 | Vm
0xEFB00040	VEXT{<c>}{<q>}.<size> {<Qd>,} <Qn>, <Qm>, #<imm>		T32		111011111 | D | 11 | Vn | Vd | imm4 | N | 1 | M | 0 | Vm

Description

Vector Extract extracts elements from the bottom end of the second operand vector and the top end of the first, concatenates them and places the result in the destination vector. The elements of the vectors are treated as being 8-bit fields. There is no distinction between data types. Depending on settings in the CPACR, NSACR, and HCPTR registers, and the Security state and PE mode in which the instruction is executed, an attempt to execute the instruction might be undefined, or trapped to Hyp mode. For more information see Enabling Advanced SIMD and floating-point support.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();  CheckAdvSIMDEnabled();
    if quadword_operation then
        Q[d>>1] = (Q[m>>1]:Q[n>>1])<position+127:position>;
    else
        D[d] = (D[m]:D[n])<position+63:position>;