ext

Extract Vector

EXT <Vd>.<T>, <Vn>.<T>, <Vm>.<T>, #<index>

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

Pseudocode Operation

concatenated ← (Vn || Vm)
byte_index ← index
if Q == 1 then
  result_bytes ← 16
else
  result_bytes ← 8
for i = 0 to result_bytes - 1 do
  Vd[i] ← concatenated[byte_index + i]
N ← unaffected; Z ← unaffected; C ← unaffected; V ← unaffected

Example

EXT v0.4s.T, v1.4s.T, v2.4s.T, #index

Encoding

Binary Layout

101110

29:24

23:22

20:16

imm4

14:11

9:5

4:0

Format SIMD Extract

Opcode 0x2E000000

Extension NEON (SIMD)

Operands

Vd
Destination SIMD/FP vector register
Vn
Low Src
Vm
High Src
index
Byte Offset

Other forms of ext

ext SVE Extract Vector

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x2E000000	EXT <Vd>.<T>, <Vn>.<T>, <Vm>.<T>, #<index>	A64	0 \| Q \| 101110 \| 00 \| 0 \| Rm \| 0 \| imm4 \| 0 \| Rn \| Rd
0x05600000	EXT <Zd>.B, { <Zn1>.B, <Zn2>.B }, #<imm>	A64	00000101011 \| imm8h \| 000 \| imm8l \| Zn \| Zd
0x05200000	EXT <Zdn>.B, <Zdn>.B, <Zm>.B, #<imm>	A64	00000101001 \| imm8h \| 000 \| imm8l \| Zm \| Zdn

Description

Extract vector from pair of vectors. This instruction extracts the lowest vector elements from the second source SIMD&FP register and the highest vector elements from the first source SIMD&FP register, concatenates the results into a vector, and writes the vector to the destination SIMD&FP register vector. The index value specifies the lowest vector element to extract from the first source register, and consecutive elements are extracted from the first, then second, source registers until the destination vector is filled. Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Operation

CheckFPAdvSIMDEnabled64();
bits(datasize) hi = V[m, datasize];
bits(datasize) lo = V[n, datasize];
bits(datasize*2) concat = hi:lo;

V[d, datasize] = concat<(position+datasize)-1:position>;

ext