ARM Instruction Reference

4.3.7CLZ

Count Leading Zeroes.

Syntax

CLZ{cond} Rd, Rm where:

cond

is an optional condition code (see Conditional execution on page 4-4).

Rd

is the ARM register for the result. Rd must not be r15.

Rm

is the operand register.

Usage

The CLZ instruction counts the number of leading zeroes in the value in Rm and returns the result in Rd. The result value is 32 if no bits are set in the source register, and zero if bit 31 is set.

Condition flags

This instruction does not affect the flags.

Architectures

This instruction is available in ARM architecture versions 5 and above.

Examples

CLZ r4,r9

CLZNE r2,r3

4-38

Copyright © 2000, 2001 ARM Limited. All rights reserved.

ARM DUI 0068B

Page 148
Image 148
ARM VERSION 1.2 manual 7 CLZ, Count Leading Zeroes, Is the ARM register for the result. Rd must not be r15