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DUP (general)

Duplicate general-purpose register to vector. This instruction duplicates the contents of the source general-purpose register into a scalar or each element in a vector, and writes the result to the SIMD&FP destination register.

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.

integer d = UInt(Rd);
integer n = UInt(Rn);

integer size = LowestSetBit(imm5);
if size > 3 then UNDEFINED;

// imm5<4:size+1> is IGNORED

if size == 3 && Q == '0' then UNDEFINED;
integer esize = 8 << size;
integer datasize = if Q == '1' then 128 else 64;
integer elements = datasize DIV esize;

Assembler Symbols


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

<T> Is an arrangement specifier, encoded in imm5:Q:
imm5 Q <T>
x0000 x RESERVED
xxxx1 0 8B
xxxx1 1 16B
xxx10 0 4H
xxx10 1 8H
xx100 0 2S
xx100 1 4S
x1000 0 RESERVED
x1000 1 2D
<R> Is the width specifier for the general-purpose source register, encoded in imm5:
imm5 <R>
xxxx1 W
xxx10 W
xx100 W
x1000 X
Unspecified bits in "imm5" are ignored but should be set to zero by an assembler.

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


bits(esize) element = X[n];
bits(datasize) result;

for e = 0 to elements-1
    Elem[result, e, esize] = element;
V[d] = result;

Operational information


  • 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.