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.

Encoding: Advanced SIMD

Variants: FEAT_AdvSIMD (ARMv8.0)

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	1	1	1	0	0	0	0						0	0	0	0	1	1
	Q	op									imm5						imm4					Rn					Rd

DUP <Vd>.<T>, <R><n>

Decoding algorithm

if !IsFeatureImplemented(FEAT_AdvSIMD) then EndOfDecode(Decode_UNDEF);
if imm5 IN 'x0000' then EndOfDecode(Decode_UNDEF);
if imm5 IN 'x1000' && Q == '0' then EndOfDecode(Decode_UNDEF);
constant integer size = LowestSetBitNZ(imm5<3:0>);

constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
// imm5<4:size+1> is IGNORED
constant integer esize = 8 << size;
constant integer datasize = 64 << UInt(Q);

Operation

CheckFPAdvSIMDEnabled64();
constant bits(esize) element = X[n, esize];
constant integer elements = datasize DIV esize;
bits(datasize) result;

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

Explanations

<Vd>: Is the name of the SIMD&FP destination register, encoded in the "Rd" field.
<T>: <R>: <n>: Is the number [0-30] of the general-purpose source register or ZR (31), encoded in the "Rn" 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.