TRN2

Transpose vectors (secondary)

This instruction reads corresponding odd-numbered vector elements from the two source SIMD&FP registers, places each result into consecutive elements of a vector, and writes the vector to the destination SIMD&FP register. Vector elements from the first source register are placed into even-numbered elements of the destination vector, starting at zero, while vector elements from the second source register are placed into odd-numbered elements of the destination vector.


Note

By using this instruction with TRN1, a 2 x 2 matrix can be transposed.


The following figure shows an example of the operation of TRN1 and TRN2 halfword operations where Q = 0.
TRN1 and TRN2 halfword operations where Q = 0

Depending on the settings in the CPACR_EL1, CPTR_EL2, and CPTR_EL3 registers, and the current Security state and Exception level, an attempt to execute the instruction might be trapped.

Advanced SIMD
(FEAT_AdvSIMD)

313029282726252423222120191817161514131211109876543210
0Q001110size0Rm011010RnRd
op

Encoding

TRN2 <Vd>.<T>, <Vn>.<T>, <Vm>.<T>

Decode for this encoding

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF); end; if size::Q == '110' then EndOfDecode(Decode_UNDEF); end; let d : integer{} = UInt(Rd); let n : integer{} = UInt(Rn); let m : integer{} = UInt(Rm); let esize : integer{} = 8 << UInt(size); let datasize : integer{} = 64 << UInt(Q); let elements : integer = datasize DIV esize; let part : integer = UInt(op); let pairs : integer = elements DIV 2;

Assembler Symbols

<Vd>

Is the name of the SIMD&FP destination register, encoded in the "Rd" field.

<T>

Is an arrangement specifier, encoded in (size :: Q):

size Q <T>
00 0 8B
00 1 16B
01 0 4H
01 1 8H
10 0 2S
10 1 4S
11 0 RESERVED
11 1 2D
<Vn>

Is the name of the first SIMD&FP source register, encoded in the "Rn" field.

<Vm>

Is the name of the second SIMD&FP source register, encoded in the "Rm" field.

Operation

AArch64_CheckFPAdvSIMDEnabled(); let operand1 : bits(datasize) = V{}(n); let operand2 : bits(datasize) = V{}(m); var result : bits(datasize); for p = 0 to pairs-1 do result[(2*p+0)*:esize] = operand1[(2*p+part)*:esize]; result[(2*p+1)*:esize] = operand2[(2*p+part)*:esize]; end; V{datasize}(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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