Arm® A64 Instruction Set Architecture: Future Architecture Technologies in the A architecture profile

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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

if !HaveSVE2() then UNDEFINED;
integer esize = 8;
integer dst = UInt(Zd);
integer s1 = UInt(Zn);
integer s2 = (s1 + 1) MOD 32;
integer position = UInt(imm8h:imm8l);

Destructive

if !HaveSVE() then UNDEFINED;
integer esize = 8;
integer dst = UInt(Zdn);
integer s1 = dst;
integer s2 = UInt(Zm);
integer position = UInt(imm8h:imm8l);

Assembler Symbols

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(VL) operand1 = Z[s1];
bits(VL) operand2 = Z[s2];
bits(VL) result;

if position >= elements then
    position = 0;

position = position << 3;
bits(VL*2) concat = operand2 : operand1;
result = concat<position+VL-1:position>;

Z[dst] = result;

Operational information

If PSTATE.DIT is 1:

• The execution time of this instruction is independent of:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.
• The response of this instruction to asynchronous exceptions does not vary based on:
  • The values of the data supplied in any of its registers.
  • The values of the NZCV flags.