CMP (immediate)

Compare (immediate)

This instruction subtracts an optionally-shifted immediate value from a register value. It updates the condition flags based on the result, and discards the result.

Encoding: Setting the condition flags

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	0	1	0																			1	1	1	1	1
sf	op	S							sh	imm12												Rn					Rd

32-bit (sf == 0)

CMP <Wn|WSP>, #<imm>{, <shift>}

Equivalent to: SUBS WZR, <Wn|WSP>, #<imm>{, <shift>}

64-bit (sf == 1)

CMP <Xn|SP>, #<imm>{, <shift>}

Equivalent to: SUBS XZR, <Xn|SP>, #<imm>{, <shift>}

Explanations

<Wn|WSP>: Is the 32-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field.
<imm>: Is an unsigned immediate, in the range 0 to 4095, encoded in the "imm12" field.
<shift>: <Xn|SP>: Is the 64-bit name of the source general-purpose register or stack pointer, 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.