ARM Cortex-M4 - Clz; Count Leading Zeros

The Cortex-M4 Instruction Set
ARM DUI 0553A Copyright © 2010 ARM. All rights reserved. 3-48
ID121610 Non-Confidential
3.5.4 CLZ
Count Leading Zeros.
Syntax
CLZ{cond} Rd, Rm
where:
cond Is an optional condition code, see Conditional execution on page 3-18.
Rd Specifies the destination register.
Rm Specifies the operand register.
Operation
The
CLZ instruction counts the number of leading zeros in the value in Rm and returns the result
in
Rd . The result value is 32 if no bits are set and zero if bit[31] is set.
Restrictions
Do not use SP and do not use PC.
Condition flags
This instruction does not change the flags.
Examples
CLZ R4,R9
CLZNE R2,R3