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Extract vector from pair of vectors

Copy the indexed byte up to the last byte of the first source vector to the bottom of the result vector, then fill the remainder of the result starting from the first byte of the second source vector. The result is placed destructively in the destination and first source vector, or constructively in the destination vector. This instruction is unpredicated.

An index that is greater than or equal to the vector length in bytes is treated as zero, resulting in the first source vector being copied to the result unchanged.

It has encodings from 2 classes: Constructive and Destructive

Constructive

(FEAT_SVE2 || FEAT_SME)

313029282726252423222120191817161514131211109876543210
00000101011imm8h000imm8lZnZd

Encoding

EXT <Zd>.B, { <Zn1>.B, <Zn2>.B }, #<imm>

Decode for this encoding

if !IsFeatureImplemented(FEAT_SVE2) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); constant integer esize = 8; constant integer dst = UInt(Zd); constant integer s1 = UInt(Zn); constant integer s2 = (s1 + 1) MOD 32; constant integer position = UInt(imm8h:imm8l) * 8;

Destructive

(FEAT_SVE || FEAT_SME)

313029282726252423222120191817161514131211109876543210
00000101001imm8h000imm8lZmZdn

Encoding

EXT <Zdn>.B, <Zdn>.B, <Zm>.B, #<imm>

Decode for this encoding

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); constant integer esize = 8; constant integer dst = UInt(Zdn); constant integer s1 = dst; constant integer s2 = UInt(Zm); constant integer position = UInt(imm8h:imm8l) * 8;

Assembler Symbols

<Zd>

Is the name of the destination scalable vector register, encoded in the "Zd" field.

<Zn1>

Is the name of the first scalable vector register of the source multi-vector group, encoded in the "Zn" field.

<Zn2>

Is the name of the second scalable vector register of the source multi-vector group, encoded in the "Zn" field.

<imm>

Is the unsigned immediate operand, in the range 0 to 255, encoded in the "imm8h:imm8l" fields.

<Zdn>

Is the name of the first source and destination scalable vector register, encoded in the "Zdn" field.

<Zm>

Is the name of the second source scalable vector register, encoded in the "Zm" field.

Operation

CheckSVEEnabled(); constant integer VL = CurrentVL; constant integer elements = VL DIV esize; constant bits(VL) operand1 = Z[s1, VL]; constant bits(VL) operand2 = Z[s2, VL]; bits(VL) result; constant bits(VL*2) concat = operand2 : operand1; if position >= VL then result = concat<VL-1:0>; else result = concat<(position+VL)-1:position>; Z[dst, VL] = result;