# _tzcnt_u32/64

Counts the number of trailing least significant zero bits in source operand and returns the result in destination. When source operand is 0, it returns its size in bits. The corresponding Intel® AVX2 instruction is TZCNT.

## Syntax

extern unsigned int _tzcnt_u32(unsigned int source);

extern unsigned __int64 _tzcnt_u64(unsigned __int64 source);

## Arguments

source | the source operand used for the operation

## Description

Searches the source operand for the least significant set bit. If a least significant 1 bit is found, its bit index is returned, otherwise the result is the number of bits in the operand size.

## Returns

Result of the operation.

Parent topic: Intrinsics for Operations to Manipulate Integer Data at Bit-Granularity