cmp

Compare (Immediate)

CMP <Wn>, #<imm>

Subtracts immediate from register, updates flags (discard result). (Alias for SUBS)

Pseudocode Operation

result ← Wn - imm
N ← result[31]
Z ← (result == 0)
C ← NOT(BorrowFrom(Wn - imm))
V ← OverflowFrom(Wn - imm)

Example

CMP w1, #16

Encoding

Binary Layout

100010

28:23

imm12

21:10

9:5

11111

4:0

Format Data Processing

Opcode 0x7100001F

Extension Base

Operands

Wn
First source / base 32-bit integer register
imm
Imm

Other forms of cmp

cmp Compare (A32)

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x6B20001F	CMP <Wn\|WSP>, <Wm>{, <extend> {#<amount>}}	A64	0 \| 1 \| 1 \| 01011 \| 00 \| 1 \| Rm \| option \| imm3 \| Rn \| 11111
0xEB20001F	CMP <Xn\|SP>, <R><m>{, <extend> {#<amount>}}	A64	1 \| 1 \| 1 \| 01011 \| 00 \| 1 \| Rm \| option \| imm3 \| Rn \| 11111
0x7100001F	CMP <Wn\|WSP>, #<imm>{, <shift>}	A64	0 \| 1 \| 1 \| 100010 \| sh \| imm12 \| Rn \| 11111
0xF100001F	CMP <Xn\|SP>, #<imm>{, <shift>}	A64	1 \| 1 \| 1 \| 100010 \| sh \| imm12 \| Rn \| 11111
0x6B00001F	CMP <Wn>, <Wm>{, <shift> #<amount>}	A64	0 \| 1 \| 1 \| 01011 \| shift \| 0 \| Rm \| imm6 \| Rn \| 11111
0xEB00001F	CMP <Xn>, <Xm>{, <shift> #<amount>}	A64	1 \| 1 \| 1 \| 01011 \| shift \| 0 \| Rm \| imm6 \| Rn \| 11111

Description

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

cmp