ARM VERSION 1.2 - Manual (Page 148)

ARM Instruction Reference
4-38 Copyright © 2000, 2001 ARM Limited. All rights reserved. ARM DUI 0068B
4.3.7 CLZ
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