INDEX (immediates)

Create index starting from and incremented by immediate

Populates the destination vector by setting the first element to the first signed immediate integer operand and monotonically incrementing the value by the second signed immediate integer operand for each subsequent element. This instruction is unpredicated.

Encoding: SVE

Variants: FEAT_SVE || FEAT_SME (FEAT_SVE || FEAT_SME)

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	0	0	0	1	0	0			1						0	1	0	0	0	0
								size			imm5b											imm5					Zd

INDEX <Zd>.<T>, #<imm1>, #<imm2>

Decoding algorithm

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then
    EndOfDecode(Decode_UNDEF);
constant integer esize = 8 << UInt(size);
constant integer d = UInt(Zd);
constant integer imm1 = SInt(imm5);
constant integer imm2 = SInt(imm5b);

Operation

CheckSVEEnabled();
constant integer VL = CurrentVL;
constant integer elements = VL DIV esize;
bits(VL) result;

for e = 0 to elements-1
    constant integer index = imm1 + e * imm2;
    Elem[result, e, esize] = index;

Z[d, VL] = result;

Explanations

<Zd>: Is the name of the destination scalable vector register, encoded in the "Zd" field.
<T>: <imm1>: Is the first signed immediate operand, in the range -16 to 15, encoded in the "imm5" field.
<imm2>: Is the second signed immediate operand, in the range -16 to 15, encoded in the "imm5b" field.

Operational Notes

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.