cmp
Compare (Immediate)
CMP <Wn>, #<imm>
Subtracts immediate from register, updates flags (discard result). (Alias for SUBS)
Details
Subtracts a 12-bit immediate value from a register and updates the condition flags based on the result; the result itself is discarded. This is an alias for SUBS with destination WZR. Sets N, Z, C, V flags according to the subtraction result. Executes in AArch64 state only.
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
0
1
1
100010
sh
imm12
Rn
11111
Operands
-
Wn
First source / base 32-bit integer register -
imm
Imm
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.