CMP (immediate) -- A64

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 for the 32-bit variant

Applies when (sf == 0)

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

is equivalent to

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

and is always the preferred disassembly.

Encoding for the 64-bit variant

Applies when (sf == 1)

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

is equivalent to

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

and is always the preferred disassembly.

Assembler Symbols

<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>

Is the optional left shift to apply to the immediate, defaulting to LSL #0 and encoded in sh:

sh	<shift>
0	LSL #0
1	LSL #12

<Xn|SP>

Is the 64-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field.

Operation

The description of SUBS (immediate) gives the operational pseudocode for this instruction.

Operational Information

The description of SUBS (immediate) gives the operational information for this instruction.

2026-03_rel 2026-03-26 20:48:11

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