UMOV

Unsigned move vector element to general-purpose register

This instruction reads the unsigned integer from the source SIMD&FP register, zero-extends it to form a 32-bit or 64-bit value, and writes the result to the destination general-purpose 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	1	1	1	1
	Q	op									imm5						imm4					Rn					Rd

32-bit (Q == 0)

UMOV <Wd>, <Vn>.<Ts>[<index>]

64-bit (Q == 1 && imm5 == x1000)

UMOV <Xd>, <Vn>.D[<index>]

Decoding algorithm

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

constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant integer esize = 8 << size;
constant integer datasize = 32 << UInt(Q);
if datasize == 64 && esize < 64 then EndOfDecode(Decode_UNDEF);
if datasize == 32 && esize >= 64 then EndOfDecode(Decode_UNDEF);
constant integer index = UInt(imm5<4:size+1>);
constant integer idxdsize = 64 << UInt(imm5<4>);

Operation

if index == 0 then
    CheckFPEnabled64();
else
    CheckFPAdvSIMDEnabled64();
constant bits(idxdsize) operand = V[n, idxdsize];

X[d, datasize] = ZeroExtend(Elem[operand, index, esize], datasize);

Explanations

<Wd>: Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.
<Vn>: Is the name of the SIMD&FP source register, encoded in the "Rn" field.
<Ts>: <index>: <index>: For the "64-bit" variant: is the element index encoded in "imm5<4>".
<Xd>: Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" 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.