3.10.2. CBZ and CBNZ

Compare and Branch on Zero, Compare and Branch on Non‑Zero.

Syntax

op{cond} Rn, label

Where:

cond

Is an optional condition code. See Conditional execution.

Rn

Is the register holding the operand.

label

Is the branch destination.

Operation

Use the CBZ or CBNZ instructions to avoid changing the condition code flags and to reduce the number of instructions.

CBZ Rn, label does not change condition flags but is otherwise equivalent to:

    CMP     Rn, #0
    BEQ     label

CBNZ Rn, label does not change condition flags but is otherwise equivalent to:

    CMP     Rn, #0
    BNE     label

Restrictions

The restrictions are:

  • Rn must be in the range of R0-R7.

  • The branch destination must be within 4 to 130 bytes after the instruction.

  • These instructions must not be used inside an IT block.

Condition flags

These instructions do not change the flags.

Examples

    CBZ    R5, target ; Forward branch if R5 is zero
    CBNZ   R0, target ; Forward branch if R0 is not zero 

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