MOVK

Move wide with keep

This instruction moves an optionally-shifted 16-bit immediate value into a register, keeping other bits unchanged.

Encoding: Immediate packed into 16-bit value and 2-bit shift

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
	1	1	1	0	0	1	0	1
sf	opc								hw		imm16																Rd

32-bit (sf == 0 && hw == 0x)

MOVK <Wd>, #<imm>{, LSL #<shift>}

64-bit (sf == 1)

MOVK <Xd>, #<imm>{, LSL #<shift>}

Decoding algorithm

if sf == '0' && hw<1> == '1' then EndOfDecode(Decode_UNDEF);

constant integer d = UInt(Rd);
constant integer datasize = 32 << UInt(sf);
constant bits(16) imm = imm16;
constant integer pos = UInt(hw) << 4;

Operation

bits(datasize) result = X[d, datasize];
result = imm;
X[d, datasize] = result;

Explanations

<Wd>: Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.
<imm>: Is the 16-bit unsigned immediate, in the range 0 to 65535, encoded in the "imm16" field.
<shift>: For the "32-bit" variant: is the amount by which to shift the immediate left, either 0 (the default) or 16, encoded in the "hw" field as <shift>/16.
<shift>: For the "64-bit" variant: is the amount by which to shift the immediate left, either 0 (the default), 16, 32 or 48, encoded in the "hw" field as <shift>/16.
<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.