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INDEX (scalar, immediate)

Create index starting from general-purpose register and incremented by immediate.

Populates the destination vector by setting the first element to the first signed scalar integer operand and monotonically incrementing the value by the second signed immediate integer operand for each subsequent element. The scalar source operand is a general-purpose register in which only the least significant bits corresponding to the vector element size are used and any remaining bits are ignored. This instruction is unpredicated.

313029282726252423222120191817161514131211109876543210
00000100size1imm5010001RnZd

SVE

INDEX <Zd>.<T>, <R><n>, #<imm>

if !HaveSVE() then UNDEFINED;
integer esize = 8 << UInt(size);
integer n = UInt(Rn);
integer d = UInt(Zd);
integer imm = SInt(imm5);

Assembler Symbols

<Zd>

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

<T> Is the size specifier, encoded in size:
size <T>
00 B
01 H
10 S
11 D
<R> Is a width specifier, encoded in size:
size <R>
01 W
x0 W
11 X
<n>

Is the number [0-30] of the source general-purpose register or the name ZR (31), encoded in the "Rn" field.

<imm>

Is the signed immediate operand, in the range -16 to 15, encoded in the "imm5" field.

Operation

CheckSVEEnabled();
integer elements = VL DIV esize;
bits(esize) operand1 = X[n];
integer element1 = SInt(operand1);
bits(VL) result;

for e = 0 to elements-1
    integer index = element1 + e * imm;
    Elem[result, e, esize] = index<esize-1:0>;

Z[d] = 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.
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