ARM Cortex-M4 - CMP and CMN; Compare and Compare Negative

The Cortex-M4 Instruction Set
ARM DUI 0553A Copyright © 2010 ARM. All rights reserved. 3-49
ID121610 Non-Confidential
3.5.5 CMP and CMN
Compare and Compare Negative.
Syntax
CMP{cond} Rn, Operand2
CMN{cond} Rn, Operand2
where:
cond Is an optional condition code, see Conditional execution on page 3-18.
Rn Specifies the register holding the first operand.
Operand2 Is a flexible second operand. See Flexible second operand on page 3-12 for
details of the options.
Operation
These instructions compare the value in a register with
Operand2 . They update the condition
flags on the result, but do not write the result to a register.
The
CMP instruction subtracts the value of Operand2 from the value in Rn . This is the same as a
SUBS instruction, except that the result is discarded.
The
CMN instruction adds the value of Operand2 to the value in Rn . This is the same as an ADDS
instruction, except that the result is discarded.
Restrictions
In these instructions:
• do not use PC
•
Operand2 must not be SP.
Condition flags
These instructions update the N, Z, C and V flags according to the result.
Examples
CMP R2, R9
CMN R0, #6400
CMPGT SP, R7, LSL #2