INDEX (scalar, immediate)

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

This instruction 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.

SVE
(FEAT_SVE || FEAT_SME)

313029282726252423222120191817161514131211109876543210
00000100size1imm5010001RnZd

Encoding

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

Decode for this encoding

if !IsFeatureImplemented(FEAT_SVE) && !IsFeatureImplemented(FEAT_SME) then EndOfDecode(Decode_UNDEF); end; let esize : integer{} = 8 << UInt(size); let n : integer = UInt(Rn); let d : integer = UInt(Zd); let imm : integer = 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>
00 W
01 W
10 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(); let VL : integer{} = CurrentVL(); let elements : integer = VL DIV esize; let operand1 : bits(esize) = X{}(n); let element1 : integer = SInt(operand1); var result : bits(VL); for e = 0 to elements-1 do let index : integer = element1 + e * imm; result[e*:esize] = index[esize-1:0]; end; Z{VL}(d) = result;

Operational information

This instruction is a data-independent-time instruction as described in About PSTATE.DIT.


2026-03_rel 2026-03-26 20:48:11

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