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AIX Version 4.3 Assembler Language Reference

cntlzd (Count Leading Zeros Double Word) Instruction

Purpose

Count the number of consecutive zero bits in the contents of a general purpose register, beginning with the high-order bit.

Syntax

PowerPC
cntlzd rA, rS (Rc=0)
cntlzd. rA, rS (Rc=1)

Description

A count of the number of consecutive zero bits, starting at bit 0 (the high-order bit) of register GPR RS is placed into GPR RA. This number ranges from 0 to 64, inclusive.

This instruction is defined only for 64-bit implementations. Using it on a 32-bit implementation will cause the system illegal instruction error handler to be invoked.

Other registers altered:

Parameters

RA Specifies the target general purpose register for the results of the instruction.
RS Specifies the source general purpose register containing the double-word to examine.

Implementation

This instruction is defined only for 64-bit implementations. Using it on a 32-bit implementation will cause the system illegal instruction error handler to be invoked.


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